Emerging Infectious Diseases: Actions Needed to Address the Challenges of Responding to Zika Virus Disease Outbreaks
Released: 2017-05-23T00:00:00


Highlights: section_title: Why GAO Did This Study
paragraphs: Zika virus disease can cause adverse pregnancy and neurological outcomes. Given this ongoing threat, GAO was asked to evaluate progress made and challenges faced by federal agencies in responding to the Zika virus outbreak in the United States.

GAO examined (1) information on what is known and not known about the epidemiology of the Zika virus, and any challenges with conducting surveillance and epidemiological studies, (2) characteristics of different diagnostic tests authorized during the outbreak, challenges test manufacturers and users faced, and the extent to which FDA and CDC followed their own communication guidance, and (3) the strengths and limitations of available mosquito control methods, and challenges federal agencies face supporting these efforts.

GAO reviewed literature and agency documentation, and interviewed federal and state officials about the Zika virus and the U.S. response. GAO also convened an expert meeting with the assistance of the National Academy of Sciences to discuss various issues surrounding the response to the Zika virus.

section_title: What GAO Found
paragraphs: Since Zika virus disease was a newly emerging disease threat in the United States, and relatively little was known about the Zika virus prior to the 2016 U.S. outbreak, the Centers for Disease Control and Prevention (CDC), and the states were not fully equipped with needed information and resources at the beginning of the outbreak. This presented several challenges for Zika virus disease surveillance and research efforts, such as challenges related to establishing a national definition for reporting cases. Knowledge about Zika virus epidemiology has increased in the past year, including information about Zika virus disease incidence and distribution of cases, and its associated adverse health outcomes. Most of the 5,197 Zika virus disease cases reported by April 5, 2017 in the United States were associated with travel from affected areas outside the continental United States. Only two states had disease cases of local, mosquito-borne transmission—216 were in Florida and 6 in Texas. While much has been learned about the epidemiology of the Zika virus, many unknowns remain, including the actual number of infections and the full spectrum of outcomes.

The 16 Zika virus diagnostic tests authorized during the outbreak varied in their performance and operational characteristics. For example, they varied in their ability to detect the virus and provide accurate results. In developing the diagnostic tests, manufacturers faced challenges in several areas, including access to clinical samples and other authorized diagnostic tests for comparison purposes. Users of the tests also encountered challenges, including determining the most accurate test to use, and obtaining equipment needed to conduct the tests. Some manufacturers raised concerns about the difficulty in developing diagnostic tests that met the Food and Drug Administration's (FDA) requirements for Emergency Use Authorization and some users expressed concerns about selecting tests amongst those authorized. GAO also determined that CDC and FDA did not follow some of their guidance in communicating with users of diagnostic tests, including providing clear information that would have enabled users to more easily compare performance across different tests.

Mosquito control programs in the United States are implemented at state and local levels and are critical to mitigating the risks associated with the Zika virus. Control methods include applying pesticides, reducing available water sources for breeding, and using personal protection. Each method has its strengths and limitations. For example, some control methods are more effective at reducing mosquito populations while others help prevent individuals from mosquito bites. Similarly, each method has some limitations, for example, there is varied public opposition to the use of certain pesticides. CDC supports state and local mosquito control activities primarily by providing guidance on mosquito control methods and funding to support certain mosquito control efforts. Challenges federal agencies faced in supporting these activities include sustaining staff expertise in mosquito control during periods when there are no outbreaks, funding constraints, and effectively communicating information about the geographical distribution of mosquitoes that transmit the Zika virus.

section_title: What GAO Recommends
paragraphs: GAO is making five recommendations to FDA and CDC, including that CDC establish a transparent process for providing test manufacturers access to diagnostic tests and FDA and CDC provide information to help ensure that users of diagnostic tests can compare performance. Agencies agreed with four recommendations but raised some concerns with the fifth. GAO has addressed these concerns in the report.

section_title: Letter
paragraphs: Emerging infectious diseases such as Zika virus disease constitute an  ongoing threat to the health of people in the United States and around the  world. Many advances in medical research and treatments were made in  the past century, but infectious diseases have been nevertheless a  leading cause of death worldwide (they account for one of every five  deaths). Additionally, infectious diseases impose a heavy societal and  economic burden on individuals, families, communities, and countries.  Infectious diseases are a continuous threat because of (1) emergence— at times rapid—of new infectious diseases; (2) reemergence of previously  known infectious diseases; and (3) persistence of intractable infectious  diseases.

Changes in human demographics, behavior, and land use—among other  factors—bring people into closer and more frequent contact with  pathogens and contribute to infectious disease emergence. This may  involve exposure to animal carriers of disease and increased  opportunities for pathogens to jump between animal and human  reservoirs. In addition to Zika virus, other examples of emerging infectious  diseases include Ebola virus disease, severe acute respiratory syndrome  (SARS), influenza, dengue, and chikungunya, among others. The Zika  virus attracted attention from health officials in the United States and  abroad after geographic and time-period similarities between reported  cases of Zika virus infection and adverse health outcomes, especially in  newborns, were reported in Brazil in 2015—a pattern that was also  observed during a Zika virus outbreak in French Polynesia in 2014.

As shown in figure 1, the Zika virus is primarily transmitted to humans by  infected mosquitoes but can also be transmitted from mother-to-child  during pregnancy or around the time of birth, or from person to person  through sexual contact or blood transfusion. The virus can cause signs  and symptoms that include fever, rash, conjunctivitis (“pink eye” where  the eyes appear red or pink), and joint and muscle pain, although most  people with Zika virus infection have only mild or no symptoms. Disease  surveillance and epidemiological studies have established that Zika virus  infection in a pregnant woman can cause birth defects in newborns and is  also associated with increased cases of nervous system illnesses in  infected adults.

Because of concern about the threat and emergence of Zika virus  disease in the United States, you asked us to review a number of issues  related to the Zika virus and the U.S. response to the outbreak. This  report (1) provides information on what is known and not known about the  epidemiology of the Zika virus and determine the challenges, if any, in  conducting surveillance and epidemiological studies, (2) determines the  characteristics of different Zika virus diagnostic tests and any challenges  manufacturers and users faced, and the extent to which the Centers for  Disease Control and Prevention (CDC) and Food and Drug  Administration (FDA) followed their own communication guidance during  the U.S. outbreak, and (3) identifies available mosquito control methods,  describes their strengths and weaknesses, and identifies any challenges  federal agencies and others face in assisting mosquito control efforts.

To conduct this work, we reviewed relevant documentation, such as  FDA’s guidance to manufacturers, product labels, and agencies’ reports  on epidemiology of the Zika virus. We also interviewed officials from key  federal agencies and departments responding to the domestic Zika virus  outbreak, including the Department of Defense (DOD), Environmental  Protection Agency (EPA), and Department of Health and Human Services  (HHS) including CDC, FDA and National Institutes of Health (NIH).

We also convened, with the assistance of the National Academy of  Sciences, a 2-day meeting with 16 experts knowledgeable about the Zika  virus to discuss issues related to the outbreak. These experts  represented academia, the federal government, state government, and  industry and combined expertise in epidemiology, diagnostic testing, and  mosquito control.

To assess the Zika virus outbreak in terms of epidemiology, diagnostic  tests, and mosquito control, we selected two cities for site visits in the  continental United States based on their reported Zika virus cases at the  time of our site visit selection: New York City, New York, which had the  largest number of cases acquired from travel outside the United States,  and Miami, Florida. Florida was the only state with local mosquito-borne  transmission at the time of our site selection. For both site visits, we  interviewed and collected information from officials in the city and state  public health departments.

To provide information on what is known about Zika virus epidemiology  and the challenges in conducting surveillance and epidemiological  studies, we reviewed surveillance case count data from CDC and data  reported jointly by the Pan American Health Organization (PAHO) and the  World Health Organization (WHO). We reviewed peer-reviewed journal  articles, agency documents, and reports about Zika virus infection and  associated health outcomes. We interviewed federal and selected state  and city officials about challenges in Zika virus surveillance and  epidemiology, including initial response efforts. We also interviewed  representatives from key public health organizations, including the  Association of State and Territorial Health Officials (ASTHO), Council of  State and Territorial Epidemiologists (CSTE), National Association of  County and City Health Officials (NACCHO), and PAHO.

To determine the characteristics of different Zika virus diagnostic tests,  we reviewed and compared the product labels, letters of authorization,  and factsheets for healthcare providers and patients for each test posted  on the FDA website in April 2017. To determine the strengths and  limitations of different diagnostic tests and the challenges associated with  Zika virus diagnostic testing, research, development, and regulatory  approval, we interviewed several manufacturers of Zika diagnostic tests.  We also interviewed officials at selected public health laboratories and  asked officials at selected federal laboratories about the strengths and  limitations of different diagnostic tests. We compared the information that  we gathered from our interviews and agency documents to Standards for  Internal Control in the Federal Government.

To determine whether CDC and FDA followed their own communication  guidance, we compared information collected from agency interviews, our  expert meeting, scientific professional societies, and relevant agencies’  documents to internal agency guidance documents, such as FDA’s  transparency initiative information.

To identify available mosquito control methods and their strengths and  limitations, we reviewed agency documents and peer-reviewed literature  and interviewed experts and officials from eight mosquito control entities.

To assess the challenges federal agencies face in assisting mosquito  control efforts in the United States, we interviewed federal agency officials  from CDC, EPA, and FDA as well as experts in the federal government,  academia, state and local governments, and experts from our meeting.  (More information on our objectives, scope, and methodology is in  appendix II.)

We conducted this performance audit from June 2016 to May 2017 in  accordance with generally accepted government auditing standards.  Those standards require that we plan and perform the audit to obtain  sufficient, appropriate evidence to provide a reasonable basis for our  findings and conclusions based on our audit objectives. We believe that  the evidence obtained provides a reasonable basis for our findings and  conclusions based on our audit objectives.
subsections: section_title: Background
subsections: section_title: Zika Virus: An Overview
paragraphs: The Zika virus is related to dengue, yellow fever, West Nile, and  Japanese encephalitis viruses, among others. The virus was first  identified in the Zika Forest in Uganda, Africa in 1947, from where it  moved east, causing only sporadic human disease until 2007. The first  documented outbreak of Zika virus disease was reported in Yap State,  Federated States of Micronesia, in 2007 and subsequent outbreaks  occurred in Southeast Asia and the Western Pacific. Some researchers  have suggested that several combined factors contributed to the current  outbreak and that travel was a major factor. Figure 2 illustrates the  spread of the Zika virus over time.

In February 2016, a WHO emergency committee on the Zika virus noted  a strong association in time and place between Zika virus infection and a  rise in detected cases of congenital malformations and neurological  complications, suspecting a causal relationship. WHO declared that the  recent cluster of microcephaly cases and other neurological disorders,  including Guillain-Barré syndrome, reported in Brazil and following a  similar cluster in French Polynesia in 2013, constituted a Public Health  Emergency of International Concern which required urgent and  coordinated research. The Secretary of Health and Human Services  also designated the Zika virus a public health emergency in Puerto Rico  in August 2016.

Microcephaly is a rare nervous system disorder that causes a baby’s  head to be smaller than expected and not fully developed, which can lead  to impaired thought processes, delayed motor function, and other adverse  outcomes. Guillain-Barré syndrome is a rare disorder in which the body’s  immune system attacks the nervous system outside the brain and spinal  cord, causing muscle weakness and, in some cases paralysis, although  most people recover.

Currently available Zika virus prevention methods include various  mosquito control and control methods, guidance on safe sex practices if a  person has or is suspected of having Zika virus or has traveled to an area  with high rates of local transmission, and guidance for travel to areas  affected by Zika virus. Although at present no vaccine has been approved  by the FDA to prevent Zika virus disease, several vaccines are in different  development phases.

section_title: Zika Virus Surveillance Overview
paragraphs: Key Terms Related to Epidemiology  Emerging Infections: Infectious disease that  is newly recognized; one that has been  recognized before but is newly appearing in a  different population or geographic area than  previously affected; one that is newly affecting  many more individuals; and/or one that has  developed new attributes (e.g., resistance or  virulence).  Epidemiology: The study of the occurrence  and distribution of health-related events,  states, and processes in specified  populations, including the study of the  determinants influencing such processes and  the application of this knowledge to control  relevant health problems.  Incidence: The number of new cases of a  disease in a defined population within a  specified time.  Incidence rate: The rate at which new events  occur in a population expressed as the  number of new cases divided by the  population at risk in a defined time period.  Outbreak: An epidemic limited to a localized  increase in the incidence of a disease as in a  village, town, or closed institution.  Surveillance: Systematic and continuous  collection, analysis, and interpretation of data,  closely integrated with the timely and coherent  dissemination of the results and assessment  to those who have the right to know so that  action can be taken.

The Zika virus was added to the list of nationally notifiable diseases in  February 2016. CDC collects data on new cases of notifiable diseases  through its National Notifiable Diseases Surveillance System (NNDSS),  by encouraging states and territories to report laboratory-confirmed  cases. Arthropod-borne viruses (also called arboviruses) are also  reported in a surveillance system that is specific to arboviral diseases,  called ArboNET. Reporting nationally notifiable diseases, including the  Zika virus, from states and territories to CDC is voluntary. States and  territories rely on healthcare providers or laboratories to report cases to  their local, state, or territorial health departments according to the laws or  regulations within their jurisdictions. A surveillance case definition is a set  of uniform criteria used to define a disease for public health surveillance,  with the purpose of enabling public health officials to classify and count  cases consistently across reporting jurisdictions.

CSTE—a professional organization of member states and territories  representing public health epidemiologists—recommends that state  health departments report cases of selected diseases to CDC’s NNDSS,  in accordance with CSTE’s position statements that establish case  definitions and are reviewed by CDC. The CSTE Zika virus interim case  definition position statement was published in February 2016 and revised  in June 2016. By April 2017, all states with the exception of Alaska, and  three U.S. territories reported Zika virus cases to CDC through the  ArboNET system, according to CDC’s reports.

To understand more about Zika virus infection, CDC established the U.S.  Zika Pregnancy Registry and is collaborating with state, tribal, local, and  territorial health departments to collect information about pregnancy and  infant outcomes following laboratory evidence of possible Zika virus  infection during pregnancy. According to CDC, the data collected through  this registry will be used to update recommendations for clinical care, to  plan for services for pregnant women and families affected by Zika virus,  and to improve prevention of Zika virus infection during pregnancy. The  Puerto Rico Department of Health and CDC developed the Zika Active  Pregnancy Surveillance System (ZAPSS)/Sistema de Vigilancia Activa de  Zika en Embarazos (SVAZE) to evaluate the association between  possible Zika virus infection during pregnancy and adverse outcomes  during pregnancy, birth, and early childhood up to 3 years of age.  Pregnant women in Puerto Rico with laboratory evidence of possible Zika  virus infection (positive or equivocal test results, regardless of whether  they have symptoms) and prenatally or perinatally exposed infants born  to these women will be actively monitored. According to CDC, this  information has been used to inform best practices in care for women  infected with Zika virus during pregnancy and their infants. CDC compiles  data from the aforementioned systems to regularly update its website  information regarding case counts and its Morbidity and Mortality Weekly  Report (MMWR) of notifiable diseases.

section_title: Diagnostic Tests for the Zika Virus
paragraphs: Accurate diagnostic tests have a key role in patient management and the  control of most infectious diseases. Good quality diagnostic tests that are  fit for purpose and can provide accurate results can help in reducing the  burden of infectious diseases. The choice of which diagnostic test to use  can depend on several factors, such as: which tests are approved for use  by regulatory authorities, which tests are available for use at the patient’s  health care location, and the physician’s decision on which of the  available tests he or she judges might be useful in clinical decision  making. Zika virus diagnostic testing is now performed in federal, state,  and commercial laboratories.

HHS, through FDA, oversees the safety and effectiveness of diagnostic  tests, which are regulated as medical devices sold in the United States.  FDA can authorize the use of unapproved medical products, including  diagnostic tests or an unapproved use of approved medical products for  certain emergencies. Under an Emergency Use Authorization (EUA),  these medical products can be used in emergencies under certain  conditions, when there are no adequate, approved, and available  alternatives. An EUA for a specific diagnostic test is intended to be  temporary and only remains in effect for the duration of the declared  emergency unless it is revoked, for example because of issues with the  diagnostic test.

Before FDA may issue an EUA, the Secretary of Health and Human  Services must declare that circumstances exist justifying the authorization  (see fig. 3). In appropriate circumstances, an HHS EUA declaration may support issuance of more than one EUA. For example, based on an HHS  EUA declaration that circumstances exist to justify the authorization of  emergency use of diagnostics for a specified biological agent, FDA may  authorize emergency use for multiple diagnostic tests to meet the need,  provided that each EUA meets the statutory criteria for issuance. The  FDA website includes a current list of available diagnostic tests and  associated letters of authorization, fact sheets, and product labels. The  letter of authorization includes the criteria for issuance, the scope of the  authorization, waiver of certain requirements, and conditions and duration  of authorization. Fact sheets are available for public health providers and  for patients. Product labels include the intended use, procedures for  conducting the test, and performance characteristics, among others.

HHS determined that the Zika virus posed a significant potential for a  public health emergency affecting national security and declared in  February 2016 that circumstances justified EUA of Zika virus diagnostic  tests. FDA’s analytical and clinical evaluation of an EUA for a medical  product is limited in comparison to the extensive evaluation required for  premarket notification (also called a 510(k) review) or premarket  approval.

Laboratory developed tests, on the other hand, are intended for clinical  use, not for commercial sale and distribution, and are designed,  manufactured and used within a single laboratory or laboratory network.  FDA has generally not enforced premarket review and other applicable  FDA requirements for laboratory developed tests because such tests are  relatively simple and generally available on a limited basis. However,  according to an expert from out meeting, laboratory developed tests have  increased in technical and analytical complexity.

FDA has authorized under EUA two different types of diagnostic tests for  the Zika virus—molecular and serologic. Molecular tests are used to  detect genetic material in samples of bodily fluids, such as serum and  urine. Serologic tests are diagnostic tests that detect antibodies against  the Zika virus in the blood. CDC manufactured and received authorization  for both types of tests, one called Trioplex (molecular) and the other,  Immunoglobulin M Antibody Capture enzyme linked immunosorbent  assay, called MAC-ELISA (serological). Trioplex is a real time reverse  transcription polymerase chain reaction test (real time RT-PCR) and the  MAC-ELISA is used to detect antibodies created against the Zika virus.

section_title: Mosquito Control EffortsMosquito Control Efforts
paragraphs: Because Zika virus disease cannot yet be prevented by drugs or  vaccines, mosquito control is critical in mitigating risks associated with  this disease. According to a CDC webpage, Zika virus is transmitted to  people mainly through the bite of infected Aedes aegypti or possibly  Aedes albopictus mosquitoes, which an article in a CDC journal reports  are present in the United States and widely distributed globally  Figure 4  shows the potential range of the Aedes aegypti and Aedes albopictus  mosquitoes in the United States. The Aedes aegypti mosquitoes are  reportedly the primary mosquito spreading Zika virus in the Americas,  while the Aedes albopictus mosquitoes share many of the same traits as  Aedes aegypti.

A female mosquito that bites someone with Zika virus of sufficient titer  can obtain the virus, allow it to multiply within it, and enter its salivary  gland such that subsequent humans bitten by this mosquito can  potentially be infected with the Zika virus. According to experts, the Aedes aegypti mosquitoes are primarily daytime biters and can bite  multiple human hosts in succession. According to the CDC, mosquito  control measures that reduce the number of potentially infectious  mosquitoes can help reduce the spread of the Zika virus.

Mosquito control in the United States is implemented and overseen at the  state and local levels, by entities such as mosquito control districts and  health agencies. CDC, using sources such as the American Mosquito  Control Association, identified over 900 entities in the United States that  perform mosquito control; however, not all geographic areas within the  United States are covered by a mosquito control entity. Federal agencies  support such control entities with funding and subject matter experts and  may regulate some control methods such as pesticides.

section_title: Federal Agency Roles in a Zika Virus Outbreak Response
paragraphs: HHS is the lead federal agency for public health and medical response to  disease outbreaks and it leverages national public health and medical  resources to prepare for and respond to disease outbreaks. For a Zika  virus response, HHS coordinates activities across federal agencies to  prevent and reduce Zika virus disease transmission and detect Zika virus  disease and infection in communities where it may emerge. It would  provide clinical guidance for diagnosis and case management. Table 1  shows the role of federal agencies and other agencies with respect to  Zika virus disease in the United States.

section_title: Challenges to Gathering New Information about Zika Virus Epidemiology
paragraphs: Surveillance and research during the recent Zika virus outbreaks in the  United States and abroad have established new information about the  epidemiology of Zika virus. Since the Zika virus was a newly emerging  infectious disease threat in the United States, and relatively little was  known about the virus prior to 2016, CDC and the states were not fully  equipped with information and resources needed for a rapid response at  the outset of the recent outbreaks. This presented surveillance and  research challenges in addressing the Zika virus knowledge gaps.
subsections: section_title: What Is Known about the Epidemiology of Zika Virus
paragraphs: Knowledge about Zika virus epidemiology has increased in the past year,  including information about Zika virus disease incidence and distribution  of cases and its associated adverse health outcomes.
subsections: section_title: Zika Virus Cases Reported in the U.S. States and Territories
paragraphs: Between January 1, 2015 and April 5, 2017, reported Zika virus disease  cases numbered 5,197 in the United States. Florida and New York had  the largest number of reported cases, followed by California and Texas.

With the exception of Alaska, every state and three territories reported at  least one Zika virus disease case by April 5, 2017. (See fig. 5.) Ten states  reported more than 100 cases each. Ninety-four percent of all cases in  U.S. states and the District of Columbia were travel-associated.  According to a CDC analysis of reported cases between January 1, 2016  and July 31, 2016 in U.S. states and the District of Columbia, 66 percent  of the 2,354 travel-related cases were associated with travel to countries  and territories in the Caribbean, followed by Central America (18 percent),  South America (10 percent), North America (5 percent), and Southeast  Asia and the Pacific Islands (<1 percent).

According to CDC, the first identified occurrence of local (mosquito-borne)  areas of transmission and the first identified outbreak of mosquito-borne  Zika virus infection in the continental United States occurred in Florida in  Miami-Dade and Broward counties during June–August, 2016. This led  to the designation of red zones for those areas and guidance for people  living in or traveling to those areas. Texas is the only other state that  has since reported locally-acquired cases. As of April 5, 2017, 216 of the  total reported cases in Florida and 6 of the total cases in Texas were  locally-acquired. Seventy-four reported cases in U.S. states and the  District of Columbia were acquired through other routes, including  maternal-fetal transmission, person-to-person through sexual  transmission, and laboratory transmission.

At 36,504 reported cases, the U.S. territories had about seven times the  number of cases as U.S. states, and most of these cases were presumed  to have been acquired through local mosquito-borne transmission; only  143 cases reported in the U.S. territories were among travelers returning  to territories from other affected areas. CDC reports that with local  transmission in the territories, it is not possible to determine whether  infection was caused by mosquito-borne or sexual transmission.

In addition to routinely updating cumulative Zika virus disease case  counts on its Zika webpage, CDC periodically publishes Zika case  demographic and other information in its MMWR. For example, 63  percent of the 2,382 Zika virus disease cases reported between January  1, 2016 and July 31, 2016 in U.S. states and the District of Columbia  were female, and the same percentage was reported in an analysis of  Puerto Rico cases between November 1, 2015 and October 20, 2016.  CDC noted that the higher proportion of women with symptomatic disease  could be because of care-seeking behavior, differential exposure to  mosquitoes or other risks, or testing of pregnant women increased.

The median age of reported Zika virus disease cases was 39 years in  U.S. states and the District of Columbia. Preliminary CDC analysis  indicated that reported cases in U.S. states typically were among older  persons compared to cases in U.S. territories. According to CDC, the age  difference observed in this preliminary analysis was most likely due to  differences in the traveler population versus the general population. The  majority of cases in U.S. states were travel-associated, while most cases  in U.S. territories were acquired through presumed local mosquito-borne  transmission, according to a CDC Zika case count update report.

section_title: Zika Virus Infection Can Cause Microcephaly and Other Adverse Health Outcomes
paragraphs: In a paper published in May 2016, CDC authors applied criteria for  causality in a review of available data and concluded that a causal  relationship exists between prenatal Zika virus infection and microcephaly  and other serious brain abnormalities. In September 2016, a WHO Zika  causality statement concluded that the most likely explanation of available  evidence from outbreaks of Zika virus infection and clusters of  microcephaly is that Zika virus infection during pregnancy is a cause of  congenital brain abnormalities including microcephaly. Other studies  have sought to estimate the risk of adverse health outcomes to pregnant  women infected with Zika virus. For example, a CDC study estimated that  the risk of microcephaly from Zika virus infection in the first trimester in  Brazil was between about 100 to 1300 cases per 10,000 births, compared  to an estimated baseline risk of 2 to 12 cases per 10,000 births.  According to CDC and WHO, microcephaly is just one of a range of birth  defects that could be related to Zika virus infection.

WHO reported that by January 18, 2017, 29 countries or territories had  reported microcephaly and other central nervous system malformations  that were potentially associated with Zika virus infection. In the United  States, the U.S. Zika Pregnancy Registry publicly reports about twice a  month the total number of pregnant women with laboratory evidence of  possible Zika virus infection who were reported to the registry. The March  28, 2017 update included 1,716 pregnant women in U.S. states and the  District of Columbia with laboratory evidence of possible Zika virus  infection. Of 1,311 completed pregnancies as of March 28, 2017 with  laboratory evidence of Zika virus infection in U.S. states and the District of  Columbia, there were 56 live born infants reported to have birth defects  and 7 pregnancy losses with birth defects. As of March 28, 2017, 3,461  pregnant women with laboratory evidence of Zika virus infection in U.S.  territories were reported to the U.S. Zika Pregnancy Registry or to the  Zika Active Pregnancy Surveillance System for Puerto Rico. CDC noted  in this update that Puerto Rico was not using the same case inclusion  criteria, and CDC was not reporting numbers for adverse pregnancy  outcomes in the territories at that time. A CDC report in April 2017  provided data on the impact of Zika virus on pregnant women and babies  for 2016, including that 44 states reported cases of pregnant women with evidence of Zika virus infection and most were travel-associated, and  about 1 in 10 pregnant women with confirmed Zika virus had a fetus or  baby with birth defects.

As of January 18, 2017, 21 countries or territories had reported an  increase in the incidence of Guillain-Barré syndrome or laboratory  confirmation of a Zika virus infection among Guillain-Barré syndrome  cases. CDC also reported that its own research suggested a strong  association between Guillain-Barré syndrome and Zika virus, but also  noted that only a small proportion of persons with a recent Zika virus  infection got Guillain-Barré syndrome. CDC reported that of 56  suspected cases of Guillain-Barré syndrome with onset of neurologic  signs identified between January 1 and July 31, 2016 in Puerto Rico, 20  patients had no evidence of Zika virus infection, compared to 34 patients  who had evidence of Zika virus or flavivirus infection.

section_title: What Is Not Known about the Epidemiology of Zika Virus
paragraphs: While much has been learned about the epidemiology of Zika virus, many  unknowns remain, including  the total number of infections;  the biological mechanisms, risks, reasons for geographic differences,  and full spectrum of outcomes associated with maternal-fetal  transmission;  the presence and duration of the virus in different bodily fluids;  the role of prior Zika virus infections or exposure to other related  flaviviruses; and  the full spectrum of outcomes of Zika virus infection.
subsections: section_title: The Total Number of Infections Is Not Known
paragraphs: Zika virus case counts obtained from the national disease surveillance  system underestimate the total number of Zika virus infections over a  specified time period, for reasons including that an infected person may not seek medical care because they have only mild or no  symptoms, or other reasons, may not be diagnosed because of limitations in Zika virus diagnostic  surveillance reporting can be incomplete for a variety of reasons.

First, the ArboNET surveillance system captures only reported Zika virus  disease and infection cases. As such, the case counts does not capture  the suspected high proportion of infected people who are asymptomatic  and may not seek care and get a diagnosis of Zika virus infection. One  study estimated that about 18 percent of Zika-infected persons will have  clinical symptoms of the infection. CDC and WHO have reported that  about 80 percent of people who have Zika virus infection won’t have any  symptoms.

Findings from a May 2017 study in Puerto Rico also suggested there is a  high rate of asymptomatic people infected with Zika virus who are not  diagnosed. The study applied results from a blood donor population that  was screened for Zika virus to estimate the number of Zika infections in  the population of Puerto Rico and estimated that there were over 450,000  Zika virus infections in Puerto Rico over approximately four months in  mid-2016. In comparison, 35,375 disease cases were reported in Puerto  Rico from January 1, 2015 through April 5, 2017, according to a CDC  Zika virus disease case count update report. The Puerto Rico blood donor  study authors concluded that results from blood donation screening  during arboviral outbreaks can supplement routine clinical and  surveillance data for improved targeting of prevention efforts.

Second, limitations in Zika virus diagnostic testing can also affect the  accuracy of the number of Zika virus cases reported in disease  surveillance due to inaccurate laboratory test results. Some Zika  diagnostic tests can determine that a recent flavivirus infection has  occurred, which may or may not be caused by Zika virus. This is because  the antibodies produced in response to flavivirus infection (Zika, dengue,  West Nile, yellow fever) are cross-reactive and may produce a positive  result in a test for any of these viruses. This is of particular concern in  areas where there has been co-circulation of flaviruses, such as dengue  virus in Puerto Rico. The ability of the test to detect the virus also  depends on the type of test used, when it is used, and the type of  specimen collected. CDC recommends additional criteria and testing  strategies for pregnant women for definitive diagnoses. The different  types of Zika virus diagnostic tests, their challenges, and testing  strategies for mitigating these challenges are discussed later in this  report.

Third, according to CDC documentation, notifiable disease reporting is  likely incomplete, and the completeness varies depending upon the  disease and the reporting state or territory. Factors that can influence  completeness of reporting include the availability of diagnostic facilities;  control measures in effect, public awareness of a specific disease, the  state and local health officials responsible for disease control and public  health surveillance, changes in methods for public health surveillance, or  introduction of new diagnostics tests or other diseases. However, CDC  documentation states that it has undertaken efforts to educate providers  on Zika virus infection and provided guidance for screening and testing.

section_title: The Biological Mechanisms, Risks, and Reasons for Geographic Differences in Outcomes Associated with Maternal-Fetal Transmission Are Unclear
paragraphs: The mechanisms of causality between Zika virus infection and  microcephaly are not well-understood. According to a recent CDC Zika  virus key messages document published on its website, questions also  remain regarding the timing, risk, and full spectrum of adverse pregnancy  outcomes as a result of Zika virus infection. Adding to the complexity,  microcephaly is also caused by other environmental and genetic factors,  including infections such as rubella during pregnancy, maternal exposure  to toxic chemicals such as heavy metals or smoking, injuries to the  developing brain, genetic abnormalities such as Down syndrome, and  severe malnutrition during fetal life.

The reasons for differences in the reported incidence of microcephaly and  other birth defects between geographic areas with Zika virus outbreaks  are also not well-understood. For example, in Brazil in 2015,  municipalities with high reports (defined as greater than 20 cases per  10,000 municipalities) of confirmed cases (per 10,000 live births) of  newborns and children with changes in growth related to Zika virus  infection and other infectious etiologies were concentrated in the  Northeast region, although there was wider dispersion in other regions in  2016.

There is also wide variation in reported microcephaly cases relative to  Zika virus cases in different countries. Using case data from PAHO, we  found a wide variation among countries in the ratio of number of reported  cases of birth defects associated with Zika virus infection to the total  number of confirmed locally-acquired and travel-associated cases of Zika  virus as of March 9, 2017 (table 2). For example, there were about 55  Zika virus cases for every birth defect case in Brazil, whereas in Colombia  there are about 77 Zika virus cases for every birth defect case.

According to literature we reviewed, some possible reasons for these  variations include differences in mosquito prevention and family planning  practices, environmental factors, population differences, and surveillance  system differences (including case definitions).

section_title: The Presence and Duration of the Virus in Different Bodily Fluids Is Not Well-Understood
paragraphs: It is not well-understood how long the Zika virus can remain in different  bodily fluids or how long it can be transmitted to other people. CDC  reports that Zika can remain in semen longer than in other bodily fluids,  including vaginal fluids, urine, and blood. One case report study found  that Zika virus was detectable in semen at 69 days after symptom  onset, and another study reported a maximum duration of Zika virus  genetic material in semen of 125 days after symptom onset.

section_title: The Role of Prior Zika Virus Infections or Exposure to Other Related Flaviviruses is Not Clear
paragraphs: The role of previous Zika virus infections or related flaviviruses such as  dengue virus is unclear. According to WHO, it is not known whether Zika  virus presence in a population over time results in widespread or low-level  immune protection or possibly no protection. The cross-reactivity  between Zika virus and related flaviviruses has not been established,  although some studies are beginning to address this gap. For example, a  study published in December 2016 suggests that preexisting dengue  virus immunity may enhance Zika virus infection and lead to greater  disease severity. Another study published in April 2017 found evidence  that antibodies against related flaviviruses such as dengue and West Nile  can cross-react with Zika virus and could increase disease severity.

section_title: The Full Spectrum of Outcomes of Zika Virus Infection is Not Known
paragraphs: The full spectrum of outcomes from maternal-fetal transmission is not  known. A paper published by CDC authors identified research gaps that  need rapid and systematic assessment, including a complete  understanding of the frequency and full spectrum of clinical outcomes  resulting from fetal Zika virus infection and of the environmental factors  that influence emergence. Another review paper noted that with  causality between Zika virus infection and adverse pregnancy outcomes  having been established, the critical research issues can turn to  understanding the full spectrum of outcomes and quantifying the relative  and absolute risks among infants who are born to women who were  infected at different times during pregnancy, and identifying factors that  modify the risk of an adverse pregnancy or birth outcome, such as coinfection with another virus, preexisting immune response to another  flavivirus, genetic background of the mother or fetus, and severity of  infection.

The associations between Zika virus infection and Guillain-Barré  syndrome are also unclear. It has been reported that the most likely  explanation of an association is that Zika virus infection can trigger  Guillain-Barré syndrome. According to CDC documentation, CDC  collaborates with state and local health departments to investigate  possibly unusually large numbers or clusters of Guillain-Barré syndrome  cases, and Puerto Rico has a surveillance system for Guillain-Barré  syndrome.

section_title: Three Key Challenges to Zika Virus Surveillance
paragraphs: CDC, CSTE, and state and local public health agencies faced several  challenges in implementing surveillance for Zika virus and its associated  health outcomes. These challenges involved establishing early case  definitions, timely communication of critical information, and  interoperability between surveillance databases.
subsections: section_title: Establishing Case Definitions Challenged the Collection of Consistent and Timely Information
paragraphs: We identified several challenges related to establishing case definitions  for Zika virus infection and disease surveillance. According to CDC  officials, typically, the process for adding a new disease to the national  notifiable disease list is that the CSTE votes during its annual meetings  whether to add the disease. If approved, the disease is usually made  notifiable the following January. According to CDC officials, this allows  time to plan and prepare for implementation, including the information  technology aspects of reporting the disease. However, because of the  emergent nature and emergency response needed for Zika virus, CSTE  released an interim case definition in February 2016 so that Zika virus  disease would become immediately notifiable.

These interim definitions included only laboratory diagnosed cases in  persons who also reported certain clinical criteria. CDC officials and  representatives from public health organizations told us that as more was  learned about Zika virus, including the need to capture asymptomatic  cases, the interim case definitions were revised. CSTE approved the  revised case definitions position statement in June 2016, which included  laboratory confirmed, asymptomatic cases (Zika virus infection) and some  revisions related to laboratory diagnostic testing.

These changes presented some challenges, according to some public  health officials and organizational representatives we interviewed. CDC  and CSTE officials told us that because there were two case definitions  approved during the year, changes had to be made to the reporting  system twice, and all cases classified according to the first definition had  to be reclassified based on the new definition, which takes time. CDC  officials also told us that another challenge is that jurisdictions use  different systems and have different capacities related to surveillance and  informatics expertise, which required a lot of resources from CDC and  others to assist these jurisdictions.

CDC officials noted that it takes time for states to reclassify their older  cases. CDC designates Zika virus cumulative case counts as provisional  on its Zika virus case counts website. CDC officials told us that cases  can be added or removed as new information becomes available, and  that due to lags in investigation, testing, and reporting, newly reported  cases often occurred weeks or even months earlier than the reported  date.

Experts at our meeting and public health officials at selected sites  emphasized the importance of educating health care providers, including  on testing and reporting guidelines. For instance, an official from one of  the selected sites stated that “a well-informed clinician is the best  reporting tool.” HHS officials told us that CDC engaged frequently with  key professional organizations such as the American College of  Obstetricians and Gynecologists to provide updated information; however  gaps remain among providers who do not access up-to-date information  provided on the CDC or professional organization websites.

section_title: Information Dissemination and Communication Were Not Always Timely
paragraphs: Public health officials from a selected site and representatives of public  health organizations had some positive things to say regarding the  assistance that federal agencies, or more specifically CDC, provided in  responding to the Zika virus outbreaks. For example, officials from one  selected site told us that a lot of guidance was coming out rapidly from  CDC, and in general the guidance was very helpful and made providers  more comfortable in patient care. Representatives from a public health  organization told us that they viewed the U.S. government’s response to  Zika as much stronger and more organized, forward leaning, inclusive,  and transparent than it was for response to some earlier diseases,  especially recognizing the many unknowns about Zika virus.  Representatives from another public health organization told us that CDC  demonstrated flexibility in its willingness to make modifications to Zika  virus reporting based on feedback from states.

Nonetheless, we identified some challenges regarding the communication  of guidance from CDC early in Zika virus surveillance implementation. For  example, officials from one selected site told us that they were sometimes  not able to get guidance consistently because entities within CDC did not  talk with each other, and that CDC could not come to a quick conclusion  about who to include in the Zika virus case definition. Representatives  from a public health organization told us that they were sometimes not  informed of changes in Zika-related information before learning about a  change from a CDC media release, but that this had improved compared  to 5 or 10 years ago.

However, according to HHS officials, CDC frequently uses media outlets  to disseminate important information to reach a broad audience. CDC  also provided updated guidance for diagnosis and clinical practice,  including several clinical guidelines and health alert network messages.

Public health officials in selected sites also told us that earlier in the Zika  virus response, challenges resulted from officials from different CDC units  needing to establish communication channels that had not existed before  the Zika virus outbreak. Officials from one selected site told us about  difficulty in communication and the importance of agency-wide  communication and partnerships, and relationships that can make things  happen faster. Officials from this site also told us that communication  across different units improved over time. CDC officials similarly told us  that many people were involved across CDC, including from birth defects  and reproductive health, and arboviral diseases units, and that rarely  were so many different people involved in a response effort.  .

section_title: The Interoperability of Surveillance Databases Was Lacking
paragraphs: There are separate systems for Zika virus cases and associated health  outcomes surveillance that collect different information but also some of  the same information, and these systems are not electronically linked.  Officials from selected sites and representatives from a public health  organization told us that having several different surveillance systems that  were not interoperable was a challenge. Representatives we interviewed  from one public health organization noted that states took issue with  having to report data to the pregnancy registry that they already reported  to other registries. Officials from one site we visited told us that there  were questions as to whether different tracking systems are necessary,  and that it is a challenge that they have different requirements. In another  selected site, officials told us it is challenging when changes need to be  made in the system because there’s no cross-communication in the data.

However, HHS officials told us that surveillance systems for infectious  diseases and surveillance of pregnancies and pregnancy outcomes and  birth defects serve very different purposes and are also tailored to each  jurisdiction’s needs. HHS officials also noted that the different and  complementary surveillance systems serve equally important, yet very  different critical needs during public health emergencies.

section_title: Two Key Challenges in Conducting Epidemiological Zika Virus Research
paragraphs: We identified two key challenges for Zika virus epidemiological research:  study designs needed for establishing association and causality  challenged linking Zika virus and associated health outcomes, and  insufficient data and lack of developed models challenged prediction of  the spread of the virus.
subsections: section_title: Establishing Association and Causality Between Zika Virus Infection and Adverse Health Outcomes Faced Study Design Challenges
paragraphs: We identified challenges in linking the Zika virus with associated health  outcomes. CDC was able to report pregnancy outcomes of women who  were infected with or are suspected to have been infected with Zika virus  and reported to the pregnancy registries. According to HHS officials,  combining this prospective monitoring of pregnant women with  retrospective birth defect surveillance allows for a comprehensive picture  of pregnancy outcomes and has already provided critical information to  inform the public health response to Zika virus. However, because the  Zika pregnancy registry only includes pregnant women who have  laboratory evidence of Zika virus infection, there is no control group of  pregnant women without Zika virus in the pregnancy registry.

According to HHS officials, studies that prospectively follow an identified  group of people over time to monitor for both disease and outcomes are  needed. WHO also noted that cohort studies of the populations currently  at risk are needed to determine both absolute and relative risks of a Zika- affected pregnancy, the role of co-factors and effect modifiers, and to  determine whether there is a specific congenital Zika virus syndrome.

NIH recently launched such a studyZika in Infants and Pregnancy (ZIP)  that aims to enroll as many as 10,000 pregnant women at up to 15 sites  in Puerto Rico and abroad in order to study the outcomes of pregnant  women who test positive for the Zika virus as well as those who test  negative and their infants. The researchers plan to compare birth  outcomes between mothers who were infected with Zika virus and those  who were not, documenting the frequency of microcephaly and other  adverse health outcomes. The study will also evaluate how the timing of  infection affects pregnancy outcomes and the role that environmental  influences, social determinants and other infections, such as dengue  fever, may have on the health of the study participants and their  newborns.

However, there are challenges in conducting prospective cohort studies  such as the ZIP study. These studies can take years before complete  results are available and published in peer-reviewed journals. For  example, the ZIP study start date was June 2016, and the estimated  study completion date is June 2018. Prospective cohort studies that  follow large numbers of individuals in multiple sites for many months or  years are also generally expensive and time-consuming.

section_title: Predicting the Spread of the Zika Virus Was Challenged by Insufficient Data and Lack of Developed Models
paragraphs: Modeling and simulation studies that accurately estimate the number of  disease cases in a population or predict cases of a disease can improve  planning and allocating scarce public health resources. According to an  April 2017 Zika virus key messages report, CDC has not been able to  predict how much the Zika virus will spread in the continental United  States. CDC officials told us that there was no epidemiologic model that  looked at both types of transmission togethersexual and mosquito- borne. In addition, there are several major assumptions that need to be  made for descriptive and predictive modeling of the Zika virus, including  the number of infections and the overall number of pregnant women.  CDC officials told us that as of October 2016, many uncertainties  remained for Zika virus modeling. The models are constantly being  refined and updated.

A December 2016 report from an intergovernmental committee on  infectious disease modeling noted the importance and potential of  outbreak prediction and modeling to improve outbreak preparedness. The  report outlined three major challenges concerning data‐ and information‐sharing, including the need for timely and  accurate data and information, especially at the beginning of a  novel disease outbreak, when knowledge about the pathogen and  data on the epidemiological situation is limited; outbreak model development and decision support, including a  systematic effort to synthesize results across modeling efforts and  support on how to use this information in outbreak response  decision-making; and science of disease emergence, which involves the need for better  understanding of the processes that drive disease emergence and  transmission well enough to predict where and when diseases are  likely to emerge.

section_title: Characteristics of Different Diagnostic Tests Varied, Manufacturers and Users Faced Several Challenges, and FDA and CDC Did Not Consistently Communicate Sufficient Information
paragraphs: Authorized diagnostic tests used for the recent Zika virus outbreak varied  in their performance and operational characteristics. Diagnostic test  manufacturers faced challenges in several areas, including research and  development, testing, and regulatory approval of these tests. Diagnostic  test users also encountered challenges, including determining the most  accurate test to use, comparing clinical performance characteristics  across tests, and obtaining equipment required to conduct authorized  tests. Both manufacturers and users we spoke with raised issues about  the EUA process. Moreover, CDC and FDA did not consistently  communicate sufficient information about Zika virus diagnostic tests that  could have enabled users to more easily identify the test that could detect  the smallest amount of virus in a sample.
subsections: section_title: Molecular and Serological Zika Virus Diagnostic Tests Varied in Performance and Operational Characteristics
paragraphs: There are currently no available diagnostic tests cleared by FDA for the  detection of Zika virus. By April 12, 2017, FDA had authorized 16  diagnostic tests for the Zika virus (13 molecular tests and 3 serologic  tests) under EUAs following the public health emergency declaration.  According to FDA officials, they revoked one test, and as a result, 15  diagnostic tests are currently authorized. These authorized diagnostic  tests for the Zika virus vary in their performance and operational  characteristics. Molecular and serologic tests have different strengths and  limitations, but some of the limitations can be mitigated by using an  algorithm that CDC published.
subsections: section_title: Molecular Tests Varied in Their Ability to Detect Zika Virus
paragraphs: Limit of detection: The measure of how

Operational characteristics: The time to  perform the test, its technical simplicity or  ease of use, user acceptability, and the  stability of the test under user conditions.  description of quality of a diagnostic test  result including the analysis of accuracy,  prevision, sensitivity, and specificity,  among others.

Authorized molecular diagnostic tests for the Zika virus varied in their  performance characteristics, and some may not have been sensitive  enough to detect Zika virus infection in samples that were collected when  the level of virus was low, namely, towards the end of, or after, the  recommended collection time post onset of symptoms. The product labels  for these authorized Zika virus diagnostic tests list a variety of different  performance characteristics, including: analytical sensitivity, cross- reactivity, interference, and clinical evaluation. The differences between  these performance characteristics are important for understanding the  accuracy of the diagnostic test. For instance, the limit of detection listed  on manufacturers’ product labels using their own samples and protocols  range from 5.9 copies/mL (less virus is needed for detection) to 42,000  copies/mL (more virus is needed for detection) (appendix V has more  details on these characteristics). If a person had 1,000 copies/mL of Zika  virus RNA in his or her blood stream, the test that had the lower limit of  detection (5.9 copies/mL) would indicate a positive result, while the test  with the higher limit of detection (42,000 copies/mL) would incorrectly  indicate a negative result (called a false negative). The limit of detection is  an important measure for the Zika virus, which can be present in relatively  low levels in the body. It is important to note that a negative result by  molecular testing should be followed by serological testing, according to  CDC’s guidance, in order to reduce the risk of false negative results.

FDA created Zika virus reference material for molecular tests to compare  test results to ensure accuracy. We found that the limit of detection varied  between different tests when performed using samples and protocols  FDA provided from 100 detectable units/mL to 30,000 detectable units/mL  (See appendix V). The diagnostic accuracy of a new test refers to the  extent of agreement between the outcome of the new test seeking  authorization and the reference standard.

According to FDA officials, when a new test is evaluated by comparison  to a nonreference standard, as with the Zika virus, one cannot directly  calculate unbiased estimates of sensitivity and specificity and therefore  these terms are not appropriate. Instead, estimates called positive  percent agreement and negative percent agreement are calculated and  reflect the agreement of the new test with the nonreference standard.  According to FDA officials, a major disadvantage with agreement  measures is that agreement is not a measure of “correctness.” The two  tests could agree; however, agreement does not indicate how good or  poor test sensitivities and specificities are (for example, both tests could  agree because they are both false negatives). Also, that two tests are not  in agreement does not necessarily mean that the new test is inaccurate  and the comparator test is correct.

section_title: Molecular Tests Varied in Ease of Use and Timeliness
paragraphs: The authorized molecular diagnostic tests for the Zika virus after the  public health emergency declaration also varied in their operational  characteristics. These molecular diagnostic tests vary in their ease of  use—some require manual steps, while others have some automation.  Automation potentially allows for faster and more consistent processing  and fewer staff resources. The time to perform individual authorized  molecular diagnostic tests for the Zika virus is around 4 hours. One  manufacturer using automation can process multiple samples in 8 hours.  However, all the authorized molecular tests for the Zika virus have to be  performed at Clinical Laboratory Improvement Amendments (CLIA) high  complexity laboratories.

section_title: Strengths and Limitations of Molecular Diagnostic Tests
paragraphs: Molecular diagnostic tests can be designed to be more specific to a single  virus and, as a result, have fewer issues with identifying the specific virus  compared to serological testing. These tests detect specific virus  sequences of genetic material. According to a manufacturer we  interviewed, some Zika virus diagnostic molecular tests detect multiple  targets, meaning a test detects multiple segments of genetic material  from the Zika virus, rendering the test more accurate since it can still  detect the virus even if there is an alteration in one of the segments that  the test is detecting. Molecular tests can also be used to simultaneously  detect other viruses such as dengue, chikungunya, and Zika (see table 3  for strengths and limitations for both types of tests).  .Molecular diagnostic tests give a definitive diagnosis independent of  other tests when the result is positive. To reliably detect the Zika virus,  molecular diagnostic tests should be performed within two weeks after  symptom onset (see fig. 6).

A negative molecular test does not rule out Zika virus infection because  the amount of virus in the sample could be too low to be detected at the  time of molecular testing. Some scientists have expressed concern over  the limit of detection of some authorized molecular diagnostic tests, which  could have resulted in missed Zika virus infections by molecular testing  and increase the need for serological follow-up testing; however,  additional testing according to CDC guidance is intended to correct these  false negative findings. An expert from our meeting stated that the  sensitivity limitation of molecular testing cannot be overcome by  additional testing if the molecular test is negative based on low levels of  virus but before the body has developed an antibody response.  Specifically, CDC guidance specifies that negative samples from  molecular tests should be sent for serology testing.

Serology tests can be used to detect the Zika virus-specific IgM  antibodies that typically develop during the first week of illness and persist  for about 12 weeks. As previously mentioned, three serological tests  were authorized for the Zika virus, of which CDC manufactured one (the  MAC-ELISA) and the two others were commercially manufactured.  Officials at a public health laboratory we interviewed said that one of the  commercially authorized tests had better specificity than the CDC MAC- ELISA when compared using 30 different samples. However, the  laboratory officials found that the commercially authorized test was easier  to perform but more time consuming to interpret and evaluate.

Manufacturers evaluated cross-reactivity by testing specimens from  patients with antibodies to other diseases that could potentially cause  false positive results. Our analysis of the data provided by manufacturers  in their EUA fact sheets and labeling found that one of the commercial  tests did not demonstrate any cross-reactivity when compared to other  flaviviruses and to nonflaviviruses during the initial qualification testing.  An expert from our meeting stated that false positives based on cross- reactivity may depend on complex mixtures of antibodies at different  states of infection, so it is complicated to assess this problem in a  comprehensive and definitive manner. However, data provided in the  EUA fact sheets and labeling for the CDC MAC-ELISA demonstrate that  this assay had significant cross reactivity to dengue virus but not to other  flaviviruses. CDC did not perform experimental studies for nonflaviviruses  for the CDC MAC-ELISA test, stating in the label that the scientific  literature indicated that only minimal cross-reactivity is expected with  antibodies against other virus families.

The positive percent agreement listed on the label for one of the  commercial tests is 100 percent, and for the CDC MAC-ELISA is 93.98  percent. The negative percent agreement is 92.5 percent for one of the  commercial tests, but the CDC MAC-ELISA does not list a negative  percent agreement in the product label. One of the commercial tests also  showed that there is no interference with substances normally found in  serum, while the CDC MAC-ELISA test did not include this information in  the product label. According to HHS officials, the three diagnostic tests  use different antigens for detection of Zika virus antibodies, which may be  cross-reactive with antibodies from related flaviviruses. According to HHS  officials, a side-by-side comparison of the performance of these  diagnostic tests has demonstrated some cross-reactivity to other  flaviviruses by each assay.

section_title: Serological Tests Varied in Their Timeliness and Throughput
paragraphs: Of the serologic tests authorized for Zika virus diagnosis, one takes three  hours and the CDC MAC-ELISA takes three days to administer. Some  diagnostic users we interviewed stated that one of the commercially  authorized tests was easier to use and a more efficient assay than the  CDC MAC-ELISA because it is automated. According to FDA, automation  decreases the time and staff required to run the samples. The CDC MAC- ELISA test takes approximately 2 to 3 days because laboratories are  required to perform two overnight incubations in the laboratory to  complete the test; in contrast one of the commercial tests only takes  about 3 hours, in part because the plates are pre-coated. Similarly, one of  the commercially authorized tests can run 28 samples per plate, while the  CDC MAC-ELISA test can run 8 samples per plate.

Diagnostic users we spoke with stated that running the CDC MAC-ELISA  in this format created issues with test throughput and capacity. One  reason for different number of samples per plate between the tests is that  the outer wells of the plates are used in one of the commercial tests and  not in the CDC MAC-ELISA test. In addition, each CDC test sample was  run in triplicate at the same time, decreasing the number of samples that  can be run at one time.

section_title: Strengths and Limitations of Serological Diagnostic Tests
paragraphs: Serologic tests for IgM can diagnose a recent infection for a wider range  of time (from about 7 days to up to 12 weeks after infection) compared to  molecular tests, which generally detect current infections. Another  strength of serologic tests is that they can be used to detect recent  exposure to the Zika virus in asymptomatic patients.

One limitation of these tests is that antibodies produced against one  flavivirus may be cross-reactive to other flaviviruses, so a positive Zika  virus IgM result does not necessarily indicate a Zika virus infection. The  reason is that related flaviviruses such as dengue, yellow fever, West  Nile, and Japanese encephalitis, which can be caused by a previous  natural infection or vaccination, can give a positive Zika virus IgM result  by a serology test. This has proven to be an issue in South America,  Central America, Mexico, and Puerto Rico, where multiple flaviviruses are  circulating, according to FDA officials.

Another limitation is that positive results need to be confirmed by using  the CDC algorithm, which can include the plaque reduction neutralizing  testing (PRNT) that is performed only at CDC or one of CDC’s designated  confirmatory testing laboratories (currently there are five designated state  public health laboratories, according to HHS officials). The PRNT  requires about six days to complete, and the logistics of specimen  shipment can further extend the time, according to HHS officials.  According to CDC officials, CDC typically takes three weeks to send  PRNT results but reporting time may be longer during the summer. Based  on our analysis of a recent FDA document, this prolonged period between  getting the IgM results and the PRNT confirmatory results may have led  some clinicians and patients to make family planning decisions without  confirmation of Zika virus infection.

Because the PRNT measures virus-specific neutralizing antibodies to  confirm infection, not only does it take more time, but it is also difficult to  perform. The test requires mixing patient serum with live Zika virus to  determine how effective the serum is at neutralizing the virus in cell  culture. However, neutralizing antibodies may still react to related  viruses. According to FDA officials, the PRNT is a well-recognized,  established standard laboratory technique and therefore did not have to  go through FDA approval or authorization. However, as mentioned above,  only a few laboratories are able to perform the PRNT for the Zika virus.  According to a CDC document, PRNT is considered the “gold-standard”  for confirmatory testing for Zika virus infection. An expert from our  meeting stated that there can still be cross-reactivity with PRNT that  confounds interpretation of the results. The five state public health  laboratories that perform Zika virus PRNT have demonstrated capacity  and proficiency to perform PRNT testing on their own, according to HHS  officials.

Finally, according to CDC officials, neutralizing antibodies to the Zika  virus develop shortly after IgM antibodies and consist primarily of IgG  antibodies. Serology testing could be used to detect IgG antibodies;  however, the United States has no EUA test for detecting Zika virus  specific IgG at this time. The associations between the Zika virus and  adverse health outcomes in newborns and the ability to detect infections  older than 12 weeks could be relevant to family planning and clinical care  of patients, if such tests were available. However, IgG is typically highly  cross-reactive to other flaviviruses and can remain elevated for years  following an infection or vaccination, so it is difficult to determine when a  patient has an elevated IgG if it is elevated for a recent infection, a prior  flavivirus infection (possibly years earlier) or both.

section_title: Overall Limitations of Diagnostic Testing Can be Addressed Through the Use of Algorithms
paragraphs: As discussed above, different types of diagnostic tests for the Zika virus  have different strengths and limitations. As a result, rather than a single  diagnostic test being considered in isolation, multiple tests and sample  types are often needed to establish a definitive laboratory diagnosis. The  window of acute Zika virus infection is small. Viral RNA is the first thing  that can be detected in an infected person in multiple specimen types. In  blood, as the immune response develops and antibodies rise, levels of  viral RNA decline.

Zika virus diagnostic tests that have been authorized since the public  health emergency declaration varied in their ability to detect the Zika virus  or antibodies to Zika virus. Consequently, a test that is less sensitive may  produce a false negative result, while a more sensitive test may detect  the virus.

CDC provides guidance for determining the order of testing (known as  testing algorithms) with different types of tests based on the strengths and  limitations of the different test types, presence of symptoms, pregnancy  status, and time between symptom onset or exposure and sample  collection. For individuals with symptoms, the time between symptom  onset and sample collection dictates test order. For pregnant women who  have no symptoms but meet certain epidemiological criteria for testing,  time between exposure or return from travel dictates test order. The  testing order algorithms are shown in table 4.

section_title: Manufacturers and Users Faced Several Challenges in Developing and Using Zika Diagnostic Tests
paragraphs: We identified five challenges that manufacturers of diagnostic tests faced  related to Zika virus diagnostic testing, research, and development, and  regulatory approval: (1) biological aspects of the virus and the immune  response, including low levels of virus in the bodily fluids of infected  patients for short periods of time and the cross-reactivity of antibodies to  other flaviviruses, (2) difficulty in accessing well-characterized clinical  samples, (3) getting access to EUA tests for use as a comparator assay,  (4) gaining cooperation with international entities, and (5) challenges  interacting with FDA during review. Challenges users of the diagnostic  tests faced included: (1) requirements to purchase new specific  equipment to be compliant with the EUA label on a test they wanted to  use; and (2) determining the most accurate test because information in  the EUA labels for some of the performance characteristics were not  easily comparable. Consequently, users could not easily compare  diagnostic test performance measures from product labels.
subsections: section_title: Manufacturers Faced Several Challenges Developing Diagnostic Tests
paragraphs: The first challenge to manufacturers developing diagnostic tests was the  lack of knowledge of Zika virus biology and infections, especially at the  beginning of the U.S. outbreak. The best sample type to use for molecular  testing was uncertain at the beginning of the outbreak. For instance, the  Zika virus had been found to be present longer in urine than in serum or  plasma, but information on just how long the virus could persist in  different bodily fluids was still evolving. Compared to related viruses, the  Zika virus is present at low levels in bodily fluids of patients during an  active infection. Manufacturers also faced challenges in identifying ways  to test for antibodies, as well as unique Zika virus antigens to target due  to issues with extensive cross-reactivity with other flaviviruses.  Information is still evolving about antigens that are unique to the Zika  virus and how long the virus persists in various bodily fluids, making it  difficult to develop diagnostic tests for the virus.

Second, the lack of well characterized clinical samples for diagnostic test  development was identified as a major challenge for developing Zika virus  diagnostic tests, according to the federal agency officials and  manufacturers we interviewed, and all the experts who participated in our  meeting. However, several manufacturers told us that obtaining samples  for testing was difficult because of high costs, potential cross-reactivity  with other flaviviruses, and an insufficient number of samples. For  example, one manufacturer had to pay more than $200,000 to acquire  samples from commercial vendors. According to another manufacturer  we interviewed, a single clinical sample for the Zika virus can cost around  $450. Manufacturers told us they requested, but were not able to obtain,  samples from CDC in the early stages of the outbreak and one  manufacturer stated this was because not enough samples were  available. One manufacturer stated that this delayed the development of  its test. According to HHS officials, to help address the lack of samples for  test development, BARDA, a component of ASPR, provided  characterized samples to test manufacturers, once the samples became  available in midsummer 2016. However, HHS officials stated that no test  manufacturer received enough samples from BARDA for the EUA testing  requirements and had to acquire samples from other sources to support  the EUA application.

BARDA officials told us they have worked closely with CDC and  manufacturers to collect and characterize clinical samples that can be  used to develop and validate diagnostic tests to detect Zika virus  infection. Manufacturers also had issues with clinical samples, since  samples sourced from Central and South America were not well  characterized, because other circulating flaviviruses could cause cross- reactivity, creating uncertainty in the outcome of a given test.

Third, FDA recommends that manufacturers perform clinical evaluation  studies that compare their tests to another “comparator” assay that is  laboratory developed, an in-house assay, or an EUA test. The selection  and quality of the comparator assay directly affects the measurements of  the test performance. A CDC document states that CDC rarely has the  resources needed to fully respond to public health emergencies but  should provide a consistent, fair, and transparent review process for all  public-private initiatives. However, according to CDC officials, they did not  make their EUA test available to some commercial manufacturers for use  as a comparator assay. One manufacturer we interviewed said its request  to CDC for reagents to perform the Trioplex test was denied since it was  a commercial manufacturer. Another manufacturer told us it attempted to  purchase an EUA test from another manufacturer but was unable to  because the other manufacturer refused to sell the EUA diagnostic test.  According to HHS officials, in order to obviate this challenge, FDA allows  manufacturers to use laboratory developed tests as comparator tests. An  expert at our meeting, stated a manufacturer had to establish their own  assay because commercial manufacturers cannot purchase the Trioplex  test or create it since it is unpublished.

Two of the 12 authorized molecular diagnostic test labels have CDC’s  Trioplex listed as their comparator assay. CDC was the first manufacturer  to receive an EUA and therefore the Trioplex test was the first authorized  molecular test that other tests attempting to get EUA could be compared  to. According to CDC officials, diagnostic tests CDC created are  distributed only to public health laboratories performing Zika virus clinical  diagnoses because in the early stage of the response, CDC did not have  the capacity to adequately support public health laboratories and also  supply commercial manufacturers with CDC tests for performance testing.  CDC officials also stated that issues with intellectual property rights, such  as patents, or material transfer agreements, may prevent sharing  reagents, individual components and technology. An expert from our  meeting stated that this could have been overcome by publishing the test  protocol with specific details about the test. However, CDC distributed its  tests to four manufacturers through technology transfers, when no  shortage of reagents was experienced by September 2016. CDC officials  we spoke with were unclear of how the process to transfer authorized  CDC tests to manufacturers originally started. Standards for Internal  Control in the Federal Government state that agencies should document  their operational processes to ensure that the organization meets its  objectives. Without a clear and transparent process for distributing CDC  diagnostic tests, the agency may not be able to develop the capacity of  the commercial sector during an outbreak.

Fourth, interacting with international entities to obtain samples and  perform testing presented some challenges. Some foreign countries have  laws that must be followed when collecting samples. A manufacturer we  interviewed faced import challenges trying to perform a diagnostic test in  another country. One manufacturer told us it took 6 weeks for diagnostic  manufacturers to ship materials to another country for testing, and the  import tax was $30,000. An expert from our meeting also stated that  obtaining CDC import permits was challenging.

Fifth, manufacturers had mixed opinions on the effectiveness of  communication from FDA. Specifically, representatives of some  manufacturers said that FDA did a good job communicating with them  throughout the EUA process during the recent outbreaks while some said  that communication with FDA could be improved. FDA interacts with  manufacturers about potential EUA products to help ensure that  manufacturers submit complete EUA applications and thereby enhances  FDA’s ability to review and ultimately authorize the EUA. FDA stated  that its review expertise is scarce, making it imperative to prioritize efforts  to move the best diagnostic tests forward first (that is, the test that is most  effective in addressing an unmet public health need). However, one  manufacturer we interviewed stated that the longer time for  communication and time to receive authorization from FDA were  challenging in developing diagnostic test for Zika virus. According to FDA,  the average time between pre-EUA, a time when FDA begins review of  fact sheets and other documentation before the submission and EUA  submission is 87.6 days, with a range of 14 to 178 days for Zika  diagnostic tests. The average time once an application was submitted to  the authorization date was 7.4 days, with a range of 1 to 26 days. A  manufacturer suggested an improvement would be to shorten the time to  respond to inquiries.

FDA developed templates for molecular and serology diagnostic tests and  sent them to manufacturers in order to support obtaining an EUA.  According to FDA officials, templates provided transparency in terms of  the studies required for a successful EUA submission and streamlined  submission for the manufacturers. FDA officials stated that updates to  studies were communicated to manufacturers as new information became  available during the Zika outbreak, including by direct communication with  manufacturers and through FDA’s webpages. As new information on Zika  virus became available, FDA instituted changes to the EUA to ensure that  manufacturers were demonstrating adequate performance for their  diagnostic tests. However, some manufacturers requested greater clarity.  Some manufacturers we interviewed stated that FDA changed its  requirements for authorization throughout the process. HHS officials  stated that they had to incorporate new information about the Zika virus  into their review process as it became available throughout the outbreak,  consequently changing the required amount of analytical and clinical data  requested from manufacturers before they could make EUA  authorizations.

section_title: Diagnostic Test Users Faced Challenges Acquiring Equipment and Determining the Most Accurate Test
paragraphs: Zika virus diagnostic test users we interviewed faced challenges because  they had to purchase new equipment to be compliant with the EUA label  on a test they wanted to use. It was difficult to determine the most  accurate test because information on the EUA labels of the performance  characteristics of tests were not comparable or not available on the CDC  website.

First, although CDC officials stated that all states had at least one public  health laboratory that had the equipment to run the CDC MAC-ELISA  test, representatives from several laboratories we interviewed stated that  they had to acquire new equipment to be able to perform a certain EUA  diagnostic test. For instance, implementation of serological testing within  another federal laboratory was delayed because additional equipment  was needed to perform the authorized test. CDC officials stated that the  agency is working to expand diagnostic testing capacity within both public  health and commercial laboratories in the United States.

Second, diagnostic test users also faced challenges in determining the  most accurate test because information on the labels was not easily  comparable. An FDA document states that the agency should share  information that is up-to-date, understandable, and easily accessible so  diagnostic test users has some basis for choosing medical products to  purchase and use. Moreover, according to this document, posting  compilation or analysis of data can benefit users since all users may not  have the ability or resources to independently analyze raw data. By  comparing the diagnostic test labels, we found that the labels had units  listed differently for key performance characteristics, data had to be  extracted from each product insert, and some of the information could not  be readily compared with other data. We also found that performance  characteristics are listed on the diagnostic test labels, but it is not  available in a consolidated format.

According to FDA officials, the agency began collecting information using  FDA Reference Materials because different manufacturers were using  different samples and potentially different methods to determine the limit  of detection of their tests. Using common samples across  manufacturers allowed FDA to directly compare the limits of detection  across different molecular diagnostic tests. However, the FDA Reference  Materials were available only after certain diagnostic tests were already  authorized under EUA. Therefore, those diagnostic test labels did not  initially list the limit of detection using the FDA Reference Materials until  their labels were updated.

FDA officials stated that if manufacturers had not previously performed  the limit of detection using the FDA Reference Materials, they would need  to perform those tests and provide results to FDA. This would allow users  to compare limits of detection for tests that were performed using the  same samples and procedures. FDA officials stated that they were  waiting to receive all the results from all the manufacturers with an  authorized diagnostic test before considering consolidating information  about performance characteristics, since this information was already  publically available in the updated product labels of the individual tests.  All authorized molecular test manufacturers had submitted limit of  detection data using the FDA Reference Materials to FDA by March 6,  2017.

Until limit of detection data have been extracted and summarized from all  the diagnostic test labels, it may be difficult and time-consuming for users  to compare the performance characteristics and results of diagnostic  tests. By waiting until FDA has all the information before compiling  information about performance characteristics, it will be time-consuming  for users to compare the limit of detection across the authorized  molecular diagnostic tests. This will become especially important with  the mosquito season approaching and public health laboratories making  decisions about which tests to use.

Another challenge users faced was related to the lack of information on  comparator assays. An FDA document recommends that there should be  a clear description of all methods used and how and what data were  collected when performing comparison testing, including a description of  the comparator assay “nonreference standard.” Experts at our meeting  agreed that identifying the comparator assay would make it easier to  compare the risks and benefits of different Zika virus diagnostic tests.  The selection and quality of the comparator assay directly affects the  legitimacy of the comparison of the test performance. When we  compared product labels for different molecular tests, we found that 6 of  12 product labels did not identify the comparator assay and that the  comparator assay could fall into one of three types: (1) another EUA test,  (2) a laboratory developed test, or (3) an in-house assay (see appendix  V).

FDA officials stated that the comparator assay for authorized diagnostic  tests can be either another authorized test or a validated reference  method and manufacturers are allowed to decide if they will identify the  comparator assay. However, the manufacturers are not required to do so.  According to FDA officials, comparison studies for EUA diagnostic tests  are based on a relatively low number of clinical specimens, and the levels  of viral RNA in a number of specimens can be low. In addition, FDA  officials stated that these two factors preclude definitive conclusions  regarding the comparative performance of devices, and FDA staff are  concerned that studies using comparator assays in labeling may be used  to make inappropriate claims and could be misinterpreted by end users.  The use of FDA Reference Material allows for a more rigorous analysis of  the comparative sensitivities of the assays from the various  manufacturers, according to FDA officials.

However, without knowing the identity of the comparator assay, it is more  difficult for users to compare performance characteristics across different  diagnostic tests and determine the most appropriate test to use.  According to an expert at our meeting, this information would be helpful  for laboratories in determining what test to use in the face of multiple  approved tests. Although the criteria for procuring diagnostic tests can  vary, for most laboratories the paramount focus is on test performance.

Standards for Internal Control in the Federal Government state that  agencies are to communicate quality information externally through  reporting lines so that external parties can help an entity achieve its  objectives and address related risks. CDC did not make publically  available data comparing the performance characteristics of different  CDC diagnostic tests that it distributed during the outbreak. CDC’s  website has information about the performance of its two authorized  diagnostic tests and the PRNT technique, but not the laboratory- developed test it distributed, called the Singleplex laboratory developed  test (Singleplex).

According to a HHS report, CDC did not provide information about one of  its diagnostic tests because it could potentially create confusion and could  have caused public health laboratories to discontinue use of the Trioplex  test, and it had not done a comprehensive comparison of the Trioplex and  Singleplex assay. Because CDC did not publically provide performance  information about its laboratory developed test—which was distributed to  some public health laboratories—questions arose regarding the sensitivity  of the two CDC tests (Singleplex and Trioplex, see text box).

A CDC scientist (who later became a whistleblower) alleged that  the Emergency Operation Center at CDC endangered public  health when it failed to disclose that an emergency use authorized  CDC test used to detect Zika virus—called the Trioplex Real-time  RT-PCR assay (Trioplex)—was substantially less sensitive than  another CDC laboratory developed test (Singleplex). After raising  concern about the test’s sensitivity, an Office of Special Counsel  (OSC) investigation was conducted.

The CDC investigation into the whistleblower’s claims did not  attempt to gather additional information on comparing the tests  from public health laboratories using the Singleplex test.  According to CDC officials, they could not do a direct comparison  of the two tests because the equipment required for both tests did  not exist at either location. The agency acknowledged that the  original Trioplex test was authorized only a smaller input volume  while the Singleplex is not subject to such limitation because it  had never been submitted to the Food and Drug Administration  (FDA) for review and was used only as a laboratory-developed  test.

OSC encouraged CDC to promote scientific debate on this issue  and said that whistleblowers should be encouraged to speak out  on matters of public concern. OSC also requested the Department  of Health and Human Services (HHS) to conduct an independent  investigation about the allegations made and CDC’s Associate  Director of Laboratory Science and Safety, who conducted the  investigation, found that the evidence did not support the  allegations. OSC found the CDC investigation reasonable. CDC  had three sources of data to compare the different tests’  sensitivities. One was from the whistleblowers’ laboratory, another  from the creator of the Trioplex test that was alleged to be less  sensitive, and the third was an independent laboratory that  compared the Singleplex and Trioplex tests.

CDC submitted a substantial amendment to the Trioplex test for  FDA’s authorization to increase the input volume of the test in  August 2016, and in January 2017 the authorization was  amended again to allow laboratories to use a singleplex reaction  on the Trioplex assay. According to CDC, the larger input volume  has been demonstrated to increase the sensitivity of the Trioplex  assay. According to a CDC website, a “head-to-head comparison  of the Trioplex test and the Zika-only assay” has not been  conducted. In HHS’ technical  comments they stated that a “head- to-head comparison of the Trioplex and the Singleplex laboratory  developed test” has been performed and showed equivalent  performance.

A journal article later showed that the original Trioplex test was  less sensitive than the Singleplex test. Increasing the input  volume of the test increased the limit of detection of the Trioplex  test approximately 20 to 50 times.

Representatives of three scientific professional societies told us that  information about the development and verification of CDC’s diagnostic  test should be made available to the scientific and medical communities.  Access to such data would provide transparency and allow for optimal  patient care, according to these representatives. According to these  societies’ representatives, the lack of access to data on test performance  prevented users from making informed decisions about which test to  adopt or recommend during the outbreak. Without including information  on the performance characteristics of tests it is distributing, CDC cannot  ensure that healthcare providers and the public have the information they  need to make informed decisions about which test is best for their use.

section_title: Mosquito Control Methods Have Strengths and Limitations, and Federal Agencies Face Several Challenges Assisting These Efforts
subsections: section_title: Mosquito Control Methods in the United States Are Often Combined Under Integrated Vector Management
paragraphs: Types of mosquito control methods available in the United States include:  (1) physical control, or nonchemical mosquito control, (2) larval mosquito  control, (3) adult mosquito control, and (4) personal protection. Mosquito  control entities and literature identified available methods that may control  mosquitoes in general. However, not all methods presented in this report  specifically apply to Aedes aegypti mosquitoes, in part because not all  such entities we spoke with had Aedes aegypti in their area. For example,  HHS identified ditching as irrelevant for Aedes aegypti mosquitoes.  These methods can be combined with surveillance of the mosquito  population, using integrated vector management (IVM) to optimize the  application of multiple methods, depending on knowledge of mosquito  biology and distribution.

Different mosquito control methods target different stages of the mosquito  lifecycle. The mosquito’s lifecycle has two stages—an aquatic stage in  which eggs develop into larvae and pupae and a terrestrial stage in which  the mosquito leaves the water, can fly, and can transmit pathogens and  lay eggs. Figure 7 depicts major lifecycle steps encompassing these  stages.

Physical control, or the use of physical or mechanical means to remove  water sources serving as larval development sites or prevent mosquito  entry into buildings, includes (1) controlling water sources needed for  mosquito breeding and (2) using barriers, such as window screens, to  keep mosquitoes away from people. A National Science and  Technology Council (NSTC) report stated that physical control includes  removing standing sources of water, such as from containers, old tires, or  blocked drains, and using well-fitted and intact screens on all house doors  and windows.

Mosquito control entity officials we interviewed told us that they use a  variety of physical control methods. For example, one told us that his  mosquito control program still benefits from ditching projects completed in  the 1960s and is continuing to use excavators to ditch areas to enhance  water run-off. Another official told us that his program includes a “drain  and cover” community outreach approach, asking residents to drain  standing water, use window screens, and wear long-sleeved clothing. A  third official we interviewed included a program for swimming pool  management by helping identify and fill in abandoned swimming pools.

Each of these physical control methods has strengths and limitations.  Specifically, officials from mosquito control entities told us that water- source control such as by large-scale ditching is very effective and avoids  the use of chemicals for certain types of mosquitoes. However, a  mosquito control entity official also said that this method is probably  challenged in the current regulatory environment. According to a NSTC  report, large-scale outdoor water source control may have limited  effectiveness against Aedes aegypti mosquitoes because breeding  requires only small volumes of water (for example, one tablespoon, under  certain conditions). Another mosquito control entity stated that inspections  of property by mosquito control personnel may be effective but are time- consuming. According to a NSTC report and mosquito control entity  officials we interviewed, such property inspections can be challenged by  privacy and property rights.

In addition, while physical control of larval development sites can reduce  or eliminate mosquito larvae, the local environment may not be suited to  such measures if extensive water bodies are present. It may be  impractical or impossible to remove or move volumes of water. For  example, a mosquito control entity official told us that since nearby  swampland cannot be removed, physical control through water  management is not an option for them.
subsections: section_title: Available Methods for Controlling Mosquito Larvae and their Strengths and Limitations
paragraphs: Controlling immature mosquitoes includes using chemical or biological  control methods. Chemical larvicides include methoprene and  pyriproxyfen, and biologically based larvicides include Bacillus  thuringiensis israelensis (Bti). CDC guidance includes another method  of larvae control—applying certain oils on water surfaces to suffocate  mosquito larvae and pupae. Mosquito control entity officials we spoke  with all told us they use larviciding, such as with Bti, or with mosquito fish  that eat mosquito larvae.

Using larvicides has strengths and limitations. Specifically, using  biologically based larvicides may be more accepted by the public than  adult pesticides, but is limited by cost and effectiveness. Officials from  mosquito control entities we spoke with told us that residents are more  accepting of biologically-based larvicides because they consider them  more natural. However, a mosquito control entity official added that  larviciding tends to be more expensive than other techniques. A mosquito  control official told us that mosquito-borne diseases have not been  successfully controlled by using larvicide alone because, while it reduces  the population by 70 percent to 80 percent, controlling a disease such as  the Zika virus disease requires a population reduction greater than 80  percent to 90 percent. Even very few mosquitoes can lead to an  outbreak or epidemic.

A mosquito control entity official told us that larvicide also needs to be  applied within a limited window of opportunity and that larvicide  application is delayed in its effect. Similarly, control using mosquito fish  appears to be “natural” to the public, but is time consuming and has  limited applicability for Aedes mosquitoes that carry the Zika virus,  because Aedes mosquito eggs can survive in small containers that dry  out.

section_title: Available Methods for Controlling Adult Mosquitoes and their Strengths and Limitations
paragraphs: Adult mosquitoes can be controlled with certain pesticides, or adulticides,  applied indoors or outdoors. An EPA official told us it has registered nine  active ingredients for use as adulticides, including malathion, naled, and  permethrin. CDC and NSTC documents indicate that some adulticides  are intended for area-wide space spraying (fogging), while others are  intended for residual spraying (in and around buildings), where   the pesticide remains active on surfaces that mosquitoes land on.  Mosquito control entity officials we spoke with said they disperse a variety  of adulticides using a variety of methods, including handheld units,  helicopters, fixed wing aircraft, and trucks. CDC guidance includes  additional methods such as nonpesticide traps—for example, CDC’s  Autocidal Gravid Ovitrap, which captures egg-laying mosquitoes on a  sticky glue.

When someone spends long periods of time  outdoors, insect repellent should be reapplied  according to product label instructions. The  best way to protect yourself and your family  from chikungunya, as well as other mosquito- borne illnesses including the Zika virus, is to  avoid being bitten by mosquitoes by using  insect repellent, wearing long sleeves and  pants, using air conditioning or window and  door screens to keep mosquitoes outside, and  reducing mosquito breeding grounds such as  standing water.

Using adulticides also has strengths and limitations. Specifically, officials  from mosquito control entities told us that adulticide spraying can be  effective in controlling mosquito populations. One mosquito control  professional noted that mosquito-borne diseases such as West Nile virus  disease have historically been controlled by adulticides. However, we  identified several limitations with adulticide spraying. One limitation  mosquito control entity officials and CDC staff identified is public  resistance to pesticides. Another limitation is that adulticiding  effectively requires control over droplet size; mosquito control entity  officials we spoke with told us they required special equipment to control  the dispersal rate and properties of the adulticides. Other limitations  include limited effectiveness under certain weather conditions and the  potentially deleterious effect of broad-spectrum adulticides on other  insects such as bees.

Additionally, Aedes aegypti mosquitoes are primarily daytime biters,  requiring spraying during certain times for optimal effectiveness.  However, one mosquito control entity official was reluctant to spray during  commuting hours, including times when schoolchildren go to or return from schools. Further, increasing resistance of mosquitoes to existing  active ingredients decreases the effectiveness of adulticiding and creates  the need for new control methods. Finally, pesticide spraying over waters  of the U.S. is subject to permit requirements under the Clean Water Act,  which may present a challenge for mosquito control entities in applying  pesticides for mosquito control (see appendix VI).

Alternative strategies may enhance the effectiveness of adulticide  application. For example, one study demonstrated that data from “contact  tracing”—which uses travel histories to help identify potential sites of  infection—can be used to target locations for indoor spraying.  According to this study, this method may reduce mosquito-borne dengue  transmission by about 90 percent. However, the method requires access  to indoor environments and permission to spray inside homes.

section_title: Available Methods for Personal Protection against Mosquitoes and their Strengths and Limitations
paragraphs: Personal protection includes using repellents, wearing long-sleeved  clothing, and using bed nets. Repellent ingredients can include dermally  applied chemicals such as DEET. Some repellents such as permethrin  can be impregnated in clothing.

Personal protection methods also have strengths and limitations.  Specifically, NSTC reports that using repellents permits individuals to  remain protected as they conduct their daily routines. While personal  protection methods are under the individual’s control, they are effective  only when properly and regularly applied. For example, one mosquito  control expert at our meeting told us that despite having authority over a  specific population, compliance related to the usage of bed nets or  repellants is still difficult to enforce.

section_title: Other Issues Related to Available Mosquito Control Efforts
paragraphs: We identified three other related issues that affect available mosquito  control efforts:  Community Awareness of Mosquito Control Efforts. NSTC reports  that the effectiveness of public-health interventions, such as mosquito  control, depends on community awareness and perception and the  implementation of control practices. The risk of the Zika virus is generally  under-perceived and misinformation is widespread about vector-control  practices. Further, communication and outreach between the mosquito  control entities and the community are necessary for effective mosquito  control. Mosquito control entity officials we spoke with agreed, noting the  importance of public education and outreach. For example, mosquito  control entity officials sometimes use a variety of approaches for such  efforts, such as going door to door, attending meetings and conferences,  holding public events at schools, buying radio time, and communicating  online. Mosquito control entity officials told us that two major challenges  that mosquito control efforts face are educating the public and ensuring  public compliance. One told us that the public generally misunderstands  mosquito control methods. Additionally, while reducing sources of water  can be effective and people tend to be receptive to such messages, they  can forget to implement them.

This “light trap” enabled CDC scientists to  venture easily into dense, remote areas when  conducting arbovirus epidemiological field  work that included capturing mosquito  vectors. The trap weighs only 1.75 pounds  and is easily repaired. Different types of traps  are used for different types of mosquitoes. For  example, the “light trap” is not used for Aedes  aegypti mosquitoes.

Mosquito Control Methods Can Be More Effective with an IVM  Approach. IVM combines control methods with surveillance of the  mosquito population. A CDC website describes IVM as combining  methods to control mosquitoes and prevent the spread of mosquito-borne  viruses based on an understanding of mosquito biology, behavior, and  spread of viruses. IVM uses methods that are safe and scientifically  proven to reduce mosquito populations when applied correctly, according  to this website. An expert from our meeting included education as a  critical component of IVM; an NSTC report describes education as a  prerequisite for successful IVM. Officials from all the mosquito control  entities we spoke with told us they use some form of IVM, and include  surveillance of the mosquito population. One mosquito control official also  noted that IVM is sometimes tailored to specific mosquito species.

Additional methods being developed may eventually be incorporated into  IVM strategies.

Mosquito Control Methods Under Development Show Promise but   Their Effectiveness Remains to be Established  Mosquito control methods under development include the use of genetically-engineered  mosquitoes and mosquitoes infected with the Wolbachia bacterium, among others.  Some of these approaches can decrease the number of offspring that survive to  adulthood. Other approaches under development can decrease the transmission of  disease-causing virus. An NSTC report stated that some reported strengths of these  approaches include potentially lower impact on other species and minimizing collateral  risks to humans by more specific targeting of mosquito species. Some potential  limitations include public opposition to some of the methods as well as a lack of studies  demonstrating their effect on mosquito-borne disease transmission.

Surveillance Helps Inform Mosquito Control Efforts. All mosquito  control entity officials we spoke with told us that they use surveillance of  the mosquito population to assess the presence and abundance of  mosquitoes and to direct the use of mosquito control methods. Traps can  be used to perform surveillance. Different traps are suited to different  species—for example, mosquito control entity officials told us that they  use BioGents-Sentinel traps to specifically target Zika virus vectors such  as Aedes aegypti and Aedes albopictus. Mosquito control entity officials  also said that sentinel animals, such as regularly monitored chickens, are  used for surveillance of mosquitoes that carry West Nile virus. One  mosquito control entity uses landing counts, which enumerate the number  of mosquitoes landing on a human volunteer over some period such as 1  minute. Finally, mosquito control entities can rely on reported mosquito  complaints from the community as part of their surveillance.

section_title: The Federal Government Faced Challenges Supporting Mosquito Control Efforts
paragraphs: The federal government has a limited role in implementing mosquito  control because mosquito control efforts are implemented at the state and  local levels. However, the federal government faced a number of  challenges in supporting these mosquito control efforts. According to  CDC documentation, the agency developed technical guidance and  provides funding and technical assistance to support state and local  mosquito control activities. We identified four challenges to the federal  government’s efforts to support mosquito control activities: (1) the timing  of the availability of funds and sustaining expertise, (2) communication of  data about mosquito distribution, (3) linking the effects of mosquito control  to disease outcomes, and (4) limited information about mosquito control  entities.
subsections: section_title: The Timing of the Availability of Funds and Sustaining Expertise
paragraphs: Federal agencies faced challenges related to the cyclic nature of  mosquito-borne diseases, including recruiting and maintaining expertise.  For example, part of IVM is matching specific methods or tools to specific  situations and requires an understanding of mosquito biology.  However, experts at our meeting identified two issues in implementing  IVM. First, one expert at our meeting said that vector biology is “ kind of a  dying field” in which “trained people cannot get jobs,” and another expert  at our meeting indicated that vector biology program support has not  been sustained. CDC officials agreed, stating that it is challenging to  study cyclic diseases such as West Nile virus. When the disease fades,  the jobs and resources also go away, so that the next time the disease  appears, staff must be retrained or new staff trained.

Second, CDC officials told us that mosquito control needs vary with  seasonal cycles, resulting in periods of several months that require more  resources followed by some periods when little or no resources are  needed. For example, CDC officials told us that even though surveillance  traps are not perishable, mosquito control entities ran out of certain traps  during the 2016 mosquito season and had to wait 6-months to acquire  new traps. According to CDC officials, funds for purchasing traps were  not available until summer.

Further, grant funds awarded for mosquito control may not make it to  some local mosquito control districts. CDC staff stated that CDC awarded  funds to combat the Zika virus, including $56 million between August and  December 2016 for mosquito control and surveillance. However, an expert at our meeting told us that CDC does not directly fund specific  mosquito control entities but instead provides funds to grant recipients,  typically states. Since the states submit the grant applications and  direct the use of certain grant funds after the award, and CDC does not  directly monitor mosquito control entities, CDC may face challenges  addressing entity needs.

section_title: CDC Faced Challenges Communicating the Presence of Mosquitoes
paragraphs: CDC faced challenges in communicating the presence of mosquitoes in a  manner that was clear and useful to different groups such as mosquito  control entities and the general public. CDC distributed maps of the  estimated potential range of the primary Zika virus vector mosquitoes on  its webpage and in guidance, but imprecision in the maps can lead to  confusion, according to some mosquito control officials. According to  CDC officials, the maps allowed states to determine the level of effort  needed for more precise mosquito surveillance as well as to show the  public where they may encounter certain mosquito species.

One mosquito control official told us that confusion about CDC’s maps  resulted from people failing to look at the qualifications stated in the map  captions and mistakenly concluding that an entire state was infested with  Zika virus vector mosquitoes. This official said that CDC’s maps of the  range of Aedes mosquitoes may be unhelpful since they are intended to  show the mosquitoes’ potential range while some residents who saw the  maps were worried that they were in an area with Zika virus. This  official also told us the maps created a challenge of reconciling  information that their own mosquito control program staff had gathered  with that presented on a highly publicized CDC map. For example, one  mosquito control entity official we spoke with told us that it has not had  Aedes aegypti in its county since 2012. However, the state where the  mosquito control entity is located is entirely within the potential range  identified by the CDC map. An expert from our meeting told us that the  CDC map showed regions painted with a broad brush, and such  information could spread fear.

To illustrate some differences between CDC’s estimated potential range  of Aedes aegypti mosquitoes and locations with reported occurrence of  the mosquito, we compared the CDC map to a map of historical mosquito  data compiled from multiple sources and published in a recent article  written by CDC scientists. The map from the article shows a different,  much sparser, pattern of recorded presence than CDC’s estimated  potential range (figure 8).

Experts identified limitations with both maps. For example, one expert  from our meeting told us that the CDC map may extend the potential  mosquito range too far north in some locations. Another expert stated that  the CDC map does not account for all the factors that affect mosquito  distribution. In addition, one expert told us that the data for the map on  the right in figure 8 may be incomplete, and a mosquito control official told  us that the map did not convey whether an area reporting no mosquitoes  had performed mosquito surveillance.

CDC officials told us that their map was generated with data ranging as  far back as 1995, and was sourced from a combination of published  records and an understanding of species ecology and U.S. geography.

However, the detailed information was not posted on the CDC website or  in documentation associated with the map. As a result, the map may  not be useful for all of its intended purposes. According to Standards for  Internal Control in the Federal Government, management should use  quality information to achieve the agency’s objectives and should select  appropriate methods to communicate externally. Additionally, the  standards state that agency management should externally communicate  necessary quality information to achieve those objectives. This includes  selecting appropriate methods to communicate externally, considering  factors such as the intended recipients and the nature of the information  being communicated. With regards to the information presented on CDC  maps, experts suggested including more details, such as (1) collection  records, (2) measures of the stability of the mosquito populations  (showing how long populations of such mosquitoes would be expected to  persist in a given location), and (3) areas of risk for transmission of  mosquito-borne diseases. Additionally, understanding the date range and  sources of the data can help place map information in context. Without  such context, CDC’s maps could generate confusion about mosquito  presence, resulting in concern among residents and public relations  challenges, among other things.

section_title: Challenges in Linking Mosquito Control Efforts to Disease Outcomes
paragraphs: CDC faced challenges in determining whether mosquito control efforts  are associated with the reduction of mosquito-borne disease. For  example, mosquito control entity officials told us the entity’s mosquito  control efforts are not directly linked to disease reduction. An official from  another mosquito control entity told us that it links mosquito control only  to the mosquito population. Another said that it links mosquito control to  the presence of West Nile virus in sentinel chickens. Additionally, West  Nile virus, CDC officials told us, is a bird disease, so CDC can surveil for  West Nile virus and detect this virus 2 weeks before it can affect  people. However, Zika virus lacks this environmental component and  enters a country with human travelers. Zika virus is thus picked up by  human surveillance before mosquito surveillance and lacks a similar 2- week delay.

Other challenges to analyzing the relationships between mosquito control  methods and disease reduction include the dependence of reported  disease cases on weather, human susceptibility and immunity. According  to CDC officials, data were insufficient to create an analogous link for the  Zika virus, in part because the specific data needed to demonstrate the  effect were not available, due to privacy considerations for individuals’  health records. Therefore, it will be difficult to tease out the effect of  mosquito control methods on disease reduction.

section_title: CDC had Limited Information on Mosquito Control Entities
paragraphs: CDC’s capacity to develop a national strategy for mosquito control is  limited and depends on its knowledge of mosquito control entities and  their capabilities. CDC relied on external sources such as the National  Pesticide Information Center, the American Mosquito Control Association,  or the National Association of County and City Health Officials to compile  a list of mosquito control entities. CDC staff told us that this list is likely to  capture the larger, well-funded entities but may miss some smaller ones.

Further, mosquito control capabilities in the United States are variable.  According to an assessment by the National Association of County and  City Health Officials, 68 percent of the responding mosquito control  entities in 10 priority jurisdictions were rated as “needs improvement.”  A mosquito control official we interviewed agreed that variability in  mosquito control entity capacities is significant. This means that it is  challenging for CDC to determine the status of mosquito control efforts in  different regions of the United States and to identify regions that may  need additional technical guidance or assistance.

section_title: Conclusions
paragraphs: Emerging infectious diseases such as influenza, Ebola and Zika viruses  represent an ongoing threat to the health of people in the United States  and worldwide. The recent Zika virus outbreak presented some  challenges, some of which are unique to Zika virus disease, in relation to  epidemiology, diagnostic tests, and federal agencies’ role in vector control  strategies.

With regard to the epidemiology of the Zika virus, CDC and its public  health partners established standardized Zika case definitions. However,  the estimated high rate of infected persons who had mild or no symptoms  and, as a result, did not seek medical treatment made it challenging to  obtain an accurate measure of the magnitude and impact of Zika virus in  the United States.

With regard to the availability of accurate and reliable diagnostic tests for  the Zika virus, FDA authorized several diagnostic tests under EUA, but  some performance characteristics were not consistently reported across  different diagnostic tests, making it more challenging to compare tests.  Information on performance characteristics presented in each diagnostic  test product label was not consolidated across available tests, and the  identity of the comparator assay was not listed on some labels, making it  challenging for users to make informed decisions about which test to  adopt or recommend to patients.

CDC developed the first two authorized diagnostic tests for the Zika virus  and offered these tests to public health laboratories, but not to some  manufacturers. Some manufacturers did not have access to the  authorized CDC tests and encountered difficulty acquiring authorized  tests from other manufacturers. Without a clear and transparent process  for distributing CDC diagnostic tests, the agency may not be able to  develop the capacity of the commercial sector to be able to meet the  needs during an outbreak.

In addition, users were not able to compare clinical performance across  authorized diagnostic tests in the absence of a diagnostic test reference  standard that all manufacturers use. CDC has not provided detailed  information on its website for all the diagnostic tests it distributed during  the Zika virus outbreak. Until CDC lists information about all the  diagnostic tests it distributes, it may be more challenging for users to  determine which test to use.

With regard to vector control methods, federal agencies can provide  important information to assist mosquito control efforts implemented at  the state and local levels. However, the information that CDC included in  its maps did not include sufficient details on its estimates of potential  distribution of mosquitoes that carry the Zika virus, which made it  challenging for mosquito control experts and the public to correctly  interpret and use such data.

section_title: Recommendations for Executive Action
paragraphs: We recommend that the Secretary of Health and Human Services direct  the Commissioner of the Food and Drug Administration to take the  following two actions:

Consolidate information from individual diagnostic test labels and  make this information available in a form that enables users to more  readily compare information across tests.

Require manufacturers to list the identity of comparator assays on  their diagnostic test labels.

We also recommend that the Secretary of Health and Human Services  direct the Director of Centers for Disease Control and Prevention to take  the following three actions:

Establish a transparent process to provide CDC diagnostic tests, upon  request, to manufacturers that are in the final stages of diagnostic test  authorization.

Include information on CDC-developed tests distributed to or shared  with public health laboratories on CDC’s website, including laboratory  developed tests.

Provide details such as collection records, dates, and data limitations  on posted and disseminated mosquito distribution maps to better  inform mosquito control experts and the general public.

section_title: Agency Comments and Our Evaluation
paragraphs: We provided a draft of this report for review and comment to HHS and  EPA. HHS’s written response is reprinted in appendix III. EPA did not  provide a written response. HHS agreed with four of our  recommendations, partially agreed with one of our recommendations and  provided information on actions it is taking to address these  recommendations. HHS and EPA also provided technical comments,  which we incorporated as appropriate.

HHS concurred with our recommendation for FDA to consolidate  information from individual product labels and said that this  information would be available on FDA’s website.

In response to our recommendation that FDA require  manufacturers to list the identity of the comparator assay, HHS  stated that it would recommend that manufacturers describe the  test used for comparison in order to reduce the risk of confusion  by diagnostic test users.

In response to our recommendation to establish a transparent  process to provide CDC diagnostic tests to manufacturers, HHS  stated that CDC will work with its existing Technology Transfer  Office to implement a transparent process for providing  manufacturers with approved CDC diagnostic assays.

In response to our recommendation that CDC provide details such  as collection records, dates, and data limitations on posted and  disseminated mosquito distribution maps to better inform mosquito  control experts and the general public, HHS described several  actions taken by CDC to help improve the quality of the data that  is used to develop estimated potential ranges of the mosquitoes  that spread Zika virus disease, including conducting a rapid review  of available data on the mosquitoes that can transmit the Zika  virus and conducting surveys to record the location of mosquitoes  capable of spreading different diseases.

In response to our recommendation to include information on  CDC-developed tests distributed to public health laboratories,  HHS partially concurred and provided clarifying information. HHS  agreed that it should share information on CDC-developed tests  that have received EUA. However, regarding this  recommendation, HHS did not agree that it should share  information on CDC’s laboratory-developed tests that have not  received EUA because CDC is unable to provide detailed  information on characteristics of these unstandardized tests. We  maintain that sharing information about these laboratory  developed tests that are used for comparison testing is important  because of the concerns that were raised regarding the sensitivity  of one of CDC’s EUA tests. We recognize that laboratory- developed tests that have not received EUA are not standardized,  but we believe that CDC can provide certain information on the  performance characteristics and quality of these tests based on its  knowledge about these tests. Sharing this information could help  other diagnostic test users make informed decisions about which  test to adopt or recommend. HHS also noted that CDC does not  distribute laboratory developed tests that have not received EUA  but in some circumstances shares them with public health  laboratories. In response to this comment, we have modified our  recommendation to reflect this information.

As agreed with your offices, we will send copies of this report to  appropriate congressional committees, the Secretary of Health and  Human Services, and the Administrator of the Environmental Protection  Agency, and other interested parties. In addition, the report will be  available at no charge on the GAO website at http://www.gao.gov.

If you or your staff members have any questions concerning this report,  please contact Timothy M. Persons, Chief Scientist, at (202) 512-6512 or  personst@gao.gov. Contact points for our Offices of Congressional  Relations and Public Affairs may be found on the last page of this report.  Key contributors to the report are listed in appendix VIII.

section_title: Appendix I: Participants in GAO’s Expert Meeting
paragraphs: This appendix lists the experts, and their affiliations, who participated in  the Zika Virus Expert Meeting held with the assistance of the National  Academies of Sciences, Engineering, and Medicine, on November 9–10,  2016, at 500 5th Street, N.W., Washington, D.C.

Amy L. Altman, Ph.D., Vice President, Biodefense and Protein  Diagnostics, Luminex Corporation  Jamie A. Blow, Ph.D., Director, Armed Forces Pest Management Board,  Defense Pest Management, Department of Defense  Michael Callahan, M.D., M.S.P.H., Director of Translational Therapeutics,  Vaccine, and Immunotherapy Center, Massachusetts General Hospital,  Harvard Medical School  Joseph M. Conlon, M.Sc., BCE, Technical Adviser, American Mosquito  Control Association  Durland Fish, Ph.D., Honorary D.Sc., Emeritus Professor, Yale School of  Public Health  Eva Harris, Ph.D., Professor, Division of Infectious Diseases and  Vaccinology, School of Public Health and Director, Center for Global  Public Health, University of California at Berkeley  Anna M. Likos, M.D., M.P.H., State Epidemiologist and Interim Deputy,  Secretary for Health, Florida Department of Health  Jorge L. Munoz-Jordan, Ph.D., Chief, Molecular Diagnostics and  Research Laboratory, Division of Vector Borne Infectious Diseases,  Dengue Branch, Centers for Disease Control and Prevention  Benjamin Pinsky, M.D., Ph.D., Medical Director, Clinical Virology  Laboratory, Stanford University School of Medicine  Brenda Rivera-García, D.V.M., M.P.H., Territorial Epidemiologist, Puerto  Rico Department of Public Health  Alfonso J. Rodriguez-Morales, M.D., Ph.D., Chair, Colombian  Collaborative Network of Zika (RECOLZIKA)

section_title: Appendix II: Objectives, Scope, and Methodology
paragraphs: The objectives of this review were to (1) provide information on what is  known and not known about the epidemiology of the Zika virus and  determine the challenges, if any, in conducting surveillance and  epidemiological studies, (2) determine the characteristics of different Zika  virus authorized diagnostic tests and any challenges manufacturers and  users faced, and the extent to which Food and Drug Administration (FDA)  and Centers for Disease Control and Prevention (CDC) followed their own  communication guidance during the U.S. outbreak, and (3) identify  available mosquito control methods, describe their strengths and  weaknesses, and identify any challenges federal agencies and others  face in assisting mosquito control efforts.

To conduct this work, we reviewed relevant laws, regulations, and  guidance. We reviewed relevant documentation such as, FDA’s guidance  to the manufacturers, product labels, and agencies reports on the  epidemiology of the Zika virus, and interviewed officials from key federal  agencies that are involved in the domestic Zika virus response. With the  assistance of the National Academy of Sciences, we convened a meeting  with 16 experts to discuss issues related to the Zika virus outbreak.  These experts represented academia, the federal government, and  industry and had combined expertise in epidemiology, diagnostics, and  mosquito control.

The Forum on Microbial Threats within the National Academies of  Sciences, Engineering, and Medicine solicited nominations for the expert  panel from its extensive contacts in academia, government, foundations,  and other organizations interested in vector borne diseases, particularly  Zika virus disease. These contacts include current and past members of  National Academies of Science’s Forum on Microbial Threats, selected  members of the National Academy of Medicine, and other National  Academies of Science stakeholders. The result was approximately 109  nominees. From this initial list, experts were selected for their knowledge  and expertise in the science and epidemiology of Zika virus, Zika virus  diagnostics, and mosquito control, as well as their experience in the  academic, industry, nonprofit, and government sectors.

We chose two U.S. cities to visit to interview about their experiences and  challenges in terms of Zika virus epidemiology, diagnostic users, and  mosquito control—namely, New York City, which had the largest reported  number of travel-associated cases, and Miami, Florida, for the largest  reported number of locally transmitted cases. For both site visits, we  interviewed and collected information from city and state public health  and mosquito officials. We also conducted site visits to three agencies  within the Department of Health and Human Services (HHS): CDC, FDA,  and National Institutes of Health (NIH).

To provide information on what is known about Zika virus epidemiology  and the challenges in conducting surveillance and epidemiologic studies,  we reviewed surveillance case data from CDC, the Pan American Health  Organization (PAHO), and the World Health Organization (WHO). We  reviewed peer-reviewed journal articles and reports about the Zika virus  and associated health outcomes. We interviewed federal and selected  state and city public health officials about Zika virus surveillance and  epidemiology. We also interviewed representatives from public health  organizations, including the Association of State and Territorial Health  Officials (ASTHO), Council of State and Territorial Epidemiologists  (CSTE), and National Association of County and City Health Officials  (NACCHO). We asked the representatives about the roles of their  organizations in Zika virus surveillance and epidemiologic studies and  any challenges they encountered.

To determine the characteristics of different Zika virus diagnostic tests,  we focused on those diagnostic tests that were authorized for use under  FDA’s Emergency Use Authorizations (EUA). This excluded laboratory  developed tests. We reviewed and compared the product labels available  on FDA’s website for 16 diagnostic tests with EUAs as of April 12, 2017.  We reviewed product labels and determined the reported limit of detection  for each molecular diagnostic test. We reviewed the product labels for  information about the FDA reference samples. We also reviewed the  letter of authorization and factsheets for healthcare providers and patients  available on FDA’s website for each authorized diagnostic test.

To determine the strengths and limitations of different diagnostic tests  and the challenges associated with Zika virus diagnostic testing,  research, development, and regulatory approval, we interviewed several  manufacturers that had an EUA diagnostic test for the Zika virus. We  attempted to interview the manufacturers of the 14 different Zika virus  diagnostic tests that had a EUA, including CDC, which manufactured two  of the diagnostic tests. We interviewed CDC officials about their tests in  site visits to Atlanta, Georgia, and Fort Collins, Colorado. We also  contacted the 14 commercial manufacturers of the EUA diagnostic tests  through email and were able to interview 10 of them that responded to  our inquiry. We used a structured set of interview questions to obtain  data from the eight manufacturers that included questions on  performance characteristics, operational characteristics, types of  samples, strengths and weakness of the diagnostic test as well as  limitations, and challenges associated with Zika diagnostic test  development, research, testing, and regulatory processes.

We also spoke with various users of the authorized diagnostic tests,  including officials from selected state public health laboratories and CDC  and Department of Defense (DOD) laboratories about the strengths and  limitations of different tests. We selected diagnostic test users by emailing  seven different entities that were listed in an HHS report as using a CDC  test in their laboratories, and we were able to interview officials at five  laboratories that responded to our inquiry. We coordinated with DOD  officials and submitted questions to their laboratories that use diagnostic  tests for Zika. We asked users of diagnostic tests about the type or types  of tests they used, how they decided on which test(s) to use, the origin of  specimens tested, the performance of comparison testing performed, and  whether they had access to information regarding the potential risks and  benefits of EUA tests and knowledge of available alternatives. We also  asked for their interpretation of an adverse event for Zika diagnostic tests.

We compared information from our interviews with federal officials and  our review of agency documents to internal controls from Standards for  Internal Control in the Federal Government. To determine current CDC  and FDA practices and whether they follow of their own communication  guidance, we compared information we collected from agency interviews  and from our expert meeting and review of relevant documentation to  internal agency guidance documents, such as the Emergency Use  Authorization of Medical Products and Related Authorities.

To identify available mosquito control methods and their strengths and  weaknesses, we reviewed agency documents and peer-reviewed  literature and conducted interviews with a nongeneralizable selection of  mosquito control entities. We focused on entities with a high potential  abundance of the mosquito species that transmit the Zika virus as  reported in a journal article and areas where there was local Zika  transmission, among other things. We emailed 13 mosquito control  entities and were able to interview eight that responded to our inquiry. We  asked these mosquito control entities about challenges with implementing  their programs, technologies they use for mosquito control, how they  select specific methods, sources of funding, and changes to their  programs because of Zika. To assess the challenges that federal  agencies face in assisting mosquito control efforts, we spoke with federal  agency officials in CDC, EPA, and FDA; experts in federal government  and academia; and members of our expert panel. The sample of  mosquito control entities we selected for our review is nongeneralizable,  meaning that information from our interviews cannot be used to make  general statements about mosquito control entities across the United  States.

We conducted this performance audit from June 2016 to May 2017 in  accordance with generally accepted government auditing standards.  Those standards require that we plan and perform the audit to obtain  sufficient, appropriate evidence to provide a reasonable basis for our  findings and conclusions based on our audit objectives. We believe that  the evidence obtained provides a reasonable basis for our findings and  conclusions based on our audit objectives.

section_title: Appendix III: Comments from the Department of Health and Human Services

section_title: Appendix IV: Zika Virus Case Definitions for National Notifiable Disease Reporting
paragraphs: The following are summarized descriptions of criteria and Zika case  classifications that were effective in June 2016, which updated interim  definitions published in February 2016.
subsections: section_title: Criteria for a Zika case
paragraphs: Criteria for laboratory evidence of recent Zika virus infection:  culture of Zika virus from blood, body fluid, or tissue; OR detection of Zika virus antigen or viral ribonucleic acid (RNA); OR positive Zika virus immunoglobulin M (IgM) antibody test with positive Zika virus neutralizing antibody titers and negative neutralizing antibody titers against dengue or other flaviviruses regularly found to the region where exposure occurred.

Criteria for laboratory evidence of recent flavivirus infection that is  possibly Zika virus:  positive Zika virus IgM antibody test with positive neutralizing antibody titers against Zika virus and dengue virus or other flaviviruses regularly found to the region where exposure occurred. positive Zika virus IgM antibody test AND negative dengue virus IgM antibody test with no neutralizing antibody testing performed.

Criteria for establishing an epidemiologic linkage:  resides in or recent travel to an area with known Zika virus transmission; OR sexual contact with a confirmed or probable case within the infection transmission risk window of Zika virus infection or person with recent travel to an area with known Zika virus transmission; OR receipt of blood or blood products within 30 days of symptom onset; OR organ or tissue transplant recipient within 30 days of symptom onset; OR association in time and place with a confirmed or probable case; OR likely vector exposure in an area with suitable seasonal and ecological  conditions for potential local vector-borne transmission.

section_title: Appendix V: Performance Characteristics Information Presented in EUA Molecular Diagnostic Tests Labels for Zika Virus

section_title: Appendix VI: Issues with Mosquito Control Pesticide Regulation
paragraphs: In discussion with mosquito control entities, we heard that certain federal  regulations related to pesticide applications may create additional issues  for mosquito control. Pesticide use for mosquito control, among other  uses, is regulated by the Federal Insecticide, Fungicide, and Rodenticide  Act (FIFRA), under which vendors register pesticides for sale or  distribution and pesticide users are required to follow the labeling for the  pesticide application. In addition to using products that have been  registered under FIFRA, mosquito control entities must obtain a permit to  spray pesticides on or near waters of the United States under the Clean  Water Act. Some mosquito control entity officials we spoke with told us  the National Pollution Discharge Elimination System (NPDES) permit  process has led to an increase in ongoing administrative burdens, such  as reporting requirements, with one stating that their burden has  increased from 1 hour of daily paperwork to 6 hours.

Mosquito control officials we interviewed told us that some mosquito  control entities have discontinued their programs, at least partly because  of additional reporting requirements under NPDES permitting. However,  an American Mosquito Control Association official told us that while they  had a number of second-hand reports, they could not specify actual  instances of entities ceasing operations because of NPDES costs. One  mosquito control official told us that NPDES permitting burdens will  largely affect smaller mosquito control entities that may not be as well  funded, many of which shut down and have not been replaced with  another entity. This official added that the entities shut partially because  of the economic downturn and that NPDES paperwork burden was a  possible, but not exclusive, cause. A mosquito control professional told us  that his program discontinued applying pesticides partly as a result of  NPDES permitting, but since the program still supplies pesticides, they  know that the use of pesticides has increased. This professional  questioned the benefit of NPDES permits if pesticide applicators react by  taking actions that result in the use of more pesticides. The American  Mosquito Control Association stated that NPDES permits duplicate FIFRA  processes, create new avenues for lawsuits, and have no substantive or  foreseeable environmental benefit.

A mosquito control official expressed support for NPDES permitting,  because following NPDES permitting guidelines allowed his program to  minimize adulticide discharges as a first response and to develop a more  desirable IVM plan. From 2012 to 2016, this entity was able to reduce  adulticiding acres by more than 30 percent, despite an increase in citizen  requests for service. However, another official stated that encouraging  larvicide use or IVM can be done more effectively than through NPDES  permitting, such as through federal funding of programs that implement  best practices.

Environmental group representatives we spoke with agreed that  documented evidence is scarce on the effects of NPDES permits on  pesticide levels in water. However, environmental group representatives  told us of benefits to the permit process, including (1) encouraging  nonchemical means of control, (2) establishing a limit on the amount of  pesticides in specific bodies of water, and (3) enabling the monitoring of  pesticide use. Representatives from one group told us that the Clean  Water Act fills a regulatory gap that FIFRA does not address.  Representatives from another group stated that the permitting application  is simple.

Further, an environmental group representative told us NPDES  notification and reporting requirements allow the public to be aware of  what is being sprayed and how much. One representative told us her  office received calls from residents wondering what was being sprayed  and saying they are not aware of requirements regarding who notifies the  public about spraying.

EPA officials told us that they have not documented evidence that (1)  pesticide use has decreased or (2) water quality has changed, in  response to NPDES permits for FIFRA-compliant pesticide application.  However, an EPA notice states that the cost of compliance with NPDES  permits is minimal. Further, EPA documentation states that EPA  disagrees that FIFRA and NPDES requirements are duplicative.  According to this documentation, NPDES permits minimize discharges of  pesticides to waters of the United States beyond FIFRA requirements,  among other things.

section_title: Appendix VII: Related GAO Products
paragraphs: Biodefense: The Nation Faces Multiple Challenges in Building and  Maintaining Biodefense and Biosurveillance. GAO-16-547T. Washington,  D.C., April 14, 2016.

Emerging Infectious Diseases: Preliminary Observations on the Zika  Virus Outbreak.GAO-16-470T. Washington, D.C., March 2, 2016  Biosurveillance: Ongoing Challenges and Future Considerations for DHS  Biosurveillance Efforts. GAO-16-413T. Washington, D.C., February 11,  2016.

Air Travel and Communicable Diseases: Comprehensive Federal Plan  Needed for U.S. Aviation System’s Preparedness. GAO-16-127.  Washington, D.C., Dec 16, 2015.

Emerging Animal Diseases: Actions Needed to Better Position USDA to  Address Future Risks. GAO-16-132. Washington, D.C., December 15,  2015.

Biosurveillance: Additional Planning, Oversight, and Coordination Needed  to Enhance National Capability. GAO-15-664T. Washington, D.C., July 8,  2015.

Biological Defense: DOD Has Strengthened Coordination on Medical  Countermeasures but Can Improve Its Process for Threat Prioritization.  GAO-14-442. Washington, D.C., May 15, 2014.

Influenza: Progress Made in Responding to Seasonal and Pandemic  Outbreaks. GAO-13-374T. Washington, D.C., February 13, 2013.

Biosurveillance: Observations on BioWatch Generation-3 and Other  Federal Efforts. GAO-12-994T. Washington, D.C., September 13, 2012.

Biosurveillance: Nonfederal Capabilities Should Be Considered in  Creating a National Biosurveillance Strategy. GAO-12-55. Washington,  D.C., October 31, 2011.

National Preparedness: Improvements Needed for Acquiring Medical  Countermeasures to Threats from Terrorism and Other Sources.  GAO-12-121. Washington, D.C., October 26, 2011.

Influenza Pandemic: Lessons from the H1N1 Pandemic Should Be  Incorporated into Future Planning. GAO-11-632. Washington, D.C., June  27, 2011.

Influenza Vaccine: Federal Investments in Alternative Technologies and  Challenges to Development and Licensure. GAO-11-435. Washington,  D.C., June 27, 2011.

Public Health Preparedness: Developing and Acquiring Medical  Countermeasures Against Chemical, Biological, Radiological, and  Nuclear Agents. GAO-11-567T. Washington, D.C., April 13, 2011.

Biosurveillance: Efforts to Develop a National Biosurveillance Capability  Need a National Strategy and a Designated Leader. GAO-10-645.  Washington, D.C., June 30, 2010.

Influenza Pandemic: Sustaining Focus on the Nation’s Planning and  Preparedness Efforts. GAO-09-334. Washington, D.C., February 2009.

Influenza Pandemic: Applying Lessons Learned from the 2004-05  Influenza Vaccine Shortage. GAO-06-221T. Washington, D.C., November  4, 2005.

West Nile Virus Outbreak: Lessons for Public Health Preparedness.  HEHS-00-180. Washington, D.C., September 11, 2000.

section_title: Appendix VIII: GAO Contacts and Staff Acknowledgments
subsections: section_title: GAO Contact

section_title: Staff Acknowledgments
paragraphs: In addition to the individual listed above, Sushil Sharma (Assistant  Director), Ashley Grant, Hayden Huang and Amber Sinclair made key  contributions to this report. Additional contributors included: Pille Anvelt,  Amy Bowser, Maureen Lackner, Penny Pickett, Paola Tena, and  Elizabeth Wood.


Question-summary annotations: questions: question: What happened due to the lack of knowledge of Zika virus?
answer: Since Zika virus disease was a newly emerging disease threat in the United States, and relatively little was known about the Zika virus prior to the 2016 U.S. outbreak, the Centers for Disease Control and Prevention (CDC), and the states were not fully equipped with needed information and resources at the beginning of the outbreak.
child_questions: question: What types of challenges emerged from this?
answer: This presented several challenges for Zika virus disease surveillance and research efforts, such as challenges related to establishing a national definition for reporting cases.

question: What more is now known about Zika virus?
answer: Knowledge about Zika virus epidemiology has increased in the past year, including information about Zika virus disease incidence and distribution of cases, and its associated adverse health outcomes.
child_questions: question: What is known about the history of Zika acquisition out of the US?
answer: Most of the 5,197 Zika virus disease cases reported by April 5, 2017 in the United States were associated with travel from affected areas outside the continental United States.

question: What is known about the history of Zika acquisition in the US?
answer: Only two states had disease cases of local, mosquito-borne transmission—216 were in Florida and 6 in Texas.

question: What is still not known about the Zika virus?
answer: While much has been learned about the epidemiology of the Zika virus, many unknowns remain, including the actual number of infections and the full spectrum of outcomes.

questions: question: How did Zika virus tests compare?
answer: The 16 Zika virus diagnostic tests authorized during the outbreak varied in their performance and operational characteristics.
child_questions: question: What was a major way they varied?
answer: For example, they varied in their ability to detect the virus and provide accurate results.

question: What issues did test manufacturers face?
answer: In developing the diagnostic tests, manufacturers faced challenges in several areas, including access to clinical samples and other authorized diagnostic tests for comparison purposes.

question: What issues did test users face?
answer: Users of the tests also encountered challenges, including determining the most accurate test to use, and obtaining equipment needed to conduct the tests.
child_questions: question: Why was the development of tests concerning to some users?
answer: Some manufacturers raised concerns about the difficulty in developing diagnostic tests that met the Food and Drug Administration's (FDA) requirements for Emergency Use Authorization and some users expressed concerns about selecting tests amongst those authorized.

question: How does the GAO determine users could have been better informed?
answer: GAO also determined that CDC and FDA did not follow some of their guidance in communicating with users of diagnostic tests, including providing clear information that would have enabled users to more easily compare performance across different tests.

questions: question: How can risks surrounding Zika virus be reduced?
answer: Mosquito control programs in the United States are implemented at state and local levels and are critical to mitigating the risks associated with the Zika virus.
child_questions: question: What different control programs are there?
answer: Control methods include applying pesticides, reducing available water sources for breeding, and using personal protection. Each method has its strengths and limitations.
child_questions: question: What different benefits do mosquito control methods provide?
answer: For example, some control methods are more effective at reducing mosquito populations while others help prevent individuals from mosquito bites.

question: What different limitations do mosquito control methods provide?
answer: Similarly, each method has some limitations, for example, there is varied public opposition to the use of certain pesticides.

question: How does the CDC support mosquito control methods?
answer: CDC supports state and local mosquito control activities primarily by providing guidance on mosquito control methods and funding to support certain mosquito control efforts.
child_questions: question: What challenges does federal support face?
answer: Challenges federal agencies faced in supporting these activities include sustaining staff expertise in mosquito control during periods when there are no outbreaks, funding constraints, and effectively communicating information about the geographical distribution of mosquitoes that transmit the Zika virus.