Puerto Rico West Nile Response Plan

Introduction

This report describes the response plan that the Puerto Rico Department of Health (PRDOH), 

working in collaboration with the Centers for Disease Control and Prevention (CDC) and other 

state and federal agencies, has implemented to address the potential arrival of West Nile virus 

(WNV) to Puerto Rico.

In 1999 West Nile virus was first detected in the United States. Since then, the infection has 

repeated itself annually, spreading through the nation from East to Southwest and being detected 

in 44 states and the District of Columbia. In 2002, it was responsible for infection in 4,156 

humans of which 284 died. It also caused infection in 14,417 horses of which approximately 

4,325 (30%) died; birds; and some other species including domestic species. Since 1999, there 

has also been evidence of WNV in Central America and the Caribbean, mostly in animals. 

Evidence of local transmission has been documented in Mexico (horses), Cayman Island (one 

human case), Dominican Republic (antibodies in birds), Jamaica (antibodies in birds) and El 

Salvador (horses). 

Even though most infections are clinically unapparent, 1 out of 5 (20%) persons infected develop 

West Nile Fever, a sickness very similar to Dengue, and 1 out of 150 develop severe neurological 

sickness. The severe phase could present meningitis, altered mental state, severe muscular 

weakness, acute flaccid paralysis, and symptoms similar to those in Polio and Parkinson. 

West Nile virus is a flavivirus transmitted primarily by the Culex pipiens mosquito, species 

commonly found throughout Puerto Rico. Because of the great possibility of WNV’s arrival to the 

Island, Puerto Rico’s Department of Health has organized a plan to address the issue to protect 

our citizens. 

This plan describes:

• the surveillance systems to identify the virus in birds and mammals, 

• the prevention, response, and control systems that will be implemented, 

• the surveillance systems to identify the virus in mosquitoes, 

• the active and passive surveillance systems for human West Nile virus cases, 

• the electronic data collection and sharing among public, state, and federal agencies 

• the public campaign for public education 

The resources allocated in this effort, including plan, infrastructure, and communication network, 

will form a cohesive multi-agency approach to respond to other similar disease events. To 

implement this plan we will require the cooperation and participation of local, state and federal 

agencies, community organizations, and specially, the general public. Working with connectivity, 

as a team, we will establish an early detection system that will minimize the risk of West Nile virus 

infection in humans and animals throughout the Island.

Surveillance

In Puerto Rico, WNV Animal Surveillance consists of laboratory testing of dead birds, birds in 

captivity, wild birds, sick and healthy horses, and canines. Human Surveillance consists of 

laboratory testing of patients with meningitis, encephalitis, acute flaccid paralysis, and other Polio, 

Guillain-Barré and Parkinson-like syndromes. 
The main goal of these surveillance systems is to detect areas of local transmission. The data 

generated by these surveillance systems will be used to release recommendations for the 

prevention and control of the disease among animals and humans throughout the Island.

Animal Surveillance

Animal surveillance has proved to be an efficient way to identify promptly WNV infection through 

different regions of the United States. Dead bird surveillance has been the one with best results. 

Birds

Dead bird surveillance

In United States, bird mortality and morbidity due WNV has been documented during the past 

transmission seasons. Researchers have found that human cases are usually preceded by 

detection of birds dead due to WNV infection. The PRDOH, in collaboration with the CDC, has 

developed a dead bird surveillance system. Personnel from the PRDOH, CDC, United States 

Fish and Wildlife Service (USFWS), United States Department of Agriculture (USDA), Puerto 

Rico Department of Agriculture (PRDA), the Department of Natural and Environmental Resources 

(DNRA) were encouraged to assist in the recollection and transportation of dead birds trough the 

island. 

This surveillance system consists of the recollection and transportation of dead birds to the 

Puerto Rico CDC - Dengue Branch Laboratory. As birds arrive to the laboratory, they will be 

tested for WNV infection. Samples will be collected by collaborating agencies and by the general 

public as well. 

A press conference, lead by the Secretary of the PRDOH, will be held at the beginning of the 

peak of transmission season (August). In this conference, the general public will be advised to 

report and transport dead birds to collection sites located through the Island. Instructions for 

proper handling of the dead birds, location, and phone numbers of collection sites will be given in 

the press conference and published in national and regional newspapers. Instructions will be 

available at the PRDOH web page (http://www.salud.gov.pr), will be given when people report by 

phone, and will be released by press communicates as required. 

Samples are transported by the Coordinator or by collaborator agencies. Carcasses will be tested 

for WNV (deep stick and PCR) by PRDOH personnel in a biosafety level 3 laboratory located at 

the Puerto Rico CDC-Dengue Branch. 

Although all dead bird species will be collected through the Island, the laboratory will only accept 

fresh carcasses with no signs of decomposition. If the number of samples submitted exceeds the 

laboratory capabilities, restrictions will be set based on location or specie type. After tests are 

conducted, results will be posted in the PRDOH web site and the CDC national database for 

arbovirus known as ARBONET. 

Wild bird surveillance

Wild bird surveillance consists of testing blood samples collected from cowbirds (Molothrus 

bonariensis) captured by DNER as part of Yellow-shouldered Blackbird Recovery Program. 

Traps are placed in the municipalities of Lajas and Cabo Rojo. Every one or two weeks, traps are 

visited and captured birds are bled prior to euthanasia (performed by DNER). In addition, there is 

a collaborative agreement with the Smithsonian Environmental Research Center and the Kansas 
University; these two institutions will conduct serological studies in wild birds in different areas in 

the Island. Wild birds will be tested for WNV antibodies (HI). 

Zoo

West Nile virus was first confirmed in a dead crow found in the Bronx Zoo in New York. Zoos 

used to monitor their animal collections very closely. The cause of death is usually investigated. 

In addition, deaths of wild birds in their facilities are also investigated, as these might have died 

from communicable diseases. 

In Puerto Rico, Island’s zoos agreed to report and summit dead bird samples (collection or wild 

birds) to the PRDOH for testing. These samples will be transported to CDC-Dengue Branch by 

the Coordinator or collaborating agencies. 

Equine surveillance

During 2002, more than 14,000 horses were reported of developing WNV infection in the United 

States. Among those, about 30% (4,325) died or were sacrificed. For this reason, in Puerto 

Rico, the general public, private veterinarians, USDA-Veterinary Services (USDA-VS) and the 

PRDA are submitting samples from sick equines. Tests performed to sick horses’ samples 

include ELISA, PCR, PRNT and HI. 

Healthy horses of different areas of the Island will be bled by collaborating veterinarians. As part 

of the equine surveillance, veterinarians will be called to follow up on potential cases. Samples 

submitted will be tested for antibodies by HI and ELISA. Equine samples are to be transported by 

the Coordinator or collaborating agencies to CDC-Dengue. 

Canine

Canine surveillance

Studies conducted in the state of Nebraska by the Nebraska Game and Park Commission 

(NGPC) and the University of Nebraska Veterinary Diagnostic Center (UNVDC) suggested that 

coyotes may serve as sentinels for WNV exposure. Using this information as a baseline, PRDOH 

decided to conduct a monthly serologic survey of wandering dogs in participating animal 

shelters. The shelters included this year are: Animal Control Solutions, Animal Control Center 

from San Juan, Animal Control Center from Caguas, Animal Control Center from Ponce, and Villa 

Michelle in Mayagüez. Blood samples acquired from dogs are to be collected by veterinary 

technicians or veterinaries and transported by the Coordinator or collaborating agencies to Puerto 

Rico CDC-Dengue Branch for further WNV testing. Canine samples are tested for antibodies by 

HI and ELISA. 

Swine

Swine serum samples are being tested by Hemaglutinin Inhibition for WNV antibodies. Samples 

will be collected from different municipalities of the Island and will be provided by the USDA-VS. 

Samples are to be transported by the Coordinator or collaborating agencies to PR CDC-Dengue 

Branch for further WNV testing. 

Mosquito

Mosquito surveillance
Even though mosquito surveillance has been conducted in the United States, in Puerto Rico it is 

not being conducted at this time. It will be considered when the virus is detected in the Island. 

Human Surveillance

Taking into account the occurrence of WNV in the United States since 1999, Puerto Rico 

Department of Health has taken the initiative to begin establishing protocols to address such a 

threat. 

Control and Prevention

Response strategies

Response strategies will be based on the potential of human infection in a particular region. 

PRDOH will work collaboratively with HAFI to implement strategies required. Right at this 

moment, Puerto Rico is situated in Response Level I.

Response 

level Circumstances Response

-Educational campaign

-Enhanced passive human and bird 

surveillance

-Consider adult mosquito surveillance, 

document species and distribution, 

lower lab testing priority

-Active bird surveillance and equine 

surveillance

-Human surveillance

I No historical or current 

evidence of virus

-Consider local disease risk 

assessments

-Enhanced educational campaign

 General public

 Provider community

-Local environmental assessments

-Local disease risk assessments

-Active human (only county with 

historical evidence) and bird 

surveillance

II Historical evidence of 

virus 

-Adult mosquito surveillance and lab 

testing

-Enhanced educational campaign

 General public

 Provider community

-Active human, bird and equine 

surveillance

III Current evidence of 

WNV presence in 

individual locations 

(virus isolation or 

evidence of infection)

-Adult mosquito surveillance, lab 

testing
 -Adult mosquito control, ground 

application

-Enhanced educational campaign

 General public

 Provider community

-Active human, bird and equine 

surveillance

-Adult mosquito surveillance, lab 

testing

IV Current evidence of 

wide-spread WNV 

presence in multiple

locations (virus 

isolation or evidence 

of infection)

-Adult mosquito control, ground 

application

Educational Campaign 

Educational campaigns will be started. They will emphasize the ways in which mosquito bites 

can be avoided (by the use of protective clothing, use of repellents, installation of screens on 

windows and doors, and avoiding activities at dawn and dusk).

These campaigns will be performed in collaboration with municipal governments, CDC, private 

industries, and schools. Posters, flyers, and coloring books will be used as educative tools. 

Mosquito Control with Non-Insecticide Methods

Citizens will be encouraged contribute in the prevention and control of a virtual epidemic. They 

will be instructed to remove standing water from pool covers, abandoned pool, rain gutters, and 

any vessel in their property that can hold water. In addition, they will be advised to introduce fish 

into ponds and decorative lakes for larval control. 

Municipal governments will be encouraged to maintain public areas free of trash, especially of 

those capable of collecting water. We will also ask for the appropriate maintenance of drainage. 

Mosquito control through the use of insecticides Appendix 1. Document prepared by 

HAFI. 

Communication plan 

The objective of the communication plan is to keep citizens informed of the surveillance findings. 

If virus transmission is detected, residents will be notified and advised through press releases to 

avoid mosquito bites and to eliminate mosquito breeding areas in their vicinity. 

All surveillance data and results will be posted in the PRDOH web page. This data will be 

regularly updated.

Acknowledgments 

Entities that are collaborating in this plan are: 

Carolina Animal Control Center 

Centers for Disease Control and Prevention 

Compañía de Parques Nacionales 
Department of Natural and Environmental Resources 

Fideicomiso de Conservación de Puerto Rico 

Humacao Animal Shelter 

Kansas University 

Ponce Animal Control Center 

Private Veterinarians and clinics 

Puerto Rico Department of Agriculture 

San Juan Animal Control Center 

Smithsonian Environmental Research Center 

Sociedad Ornitológica de Puerto Rico 

United States Department of Agriculture 

United States Fish and Wildlife Service 

Villa Michelle Animal Shelter in Mayagüez 

Appendix I. HAFI’s WNV Response Plan

Appendix II. PRDOH WNV Response Plan