As of June 16, 2016, the World Health Organization (WHO) reported that 60 countries worldwide had experienced mosquito-borne transmission of Zika, 46 of which had never had Zika cases before (see Figure 1 ). The U.S. Centers for Disease Control and Prevention (CDC) has concluded that Zika causes microc ephaly (a serious birth defect involving brain damage) and is associated with Guillain-Barré syndrome (GBS, a neurological condition) and other neurological and autoimmune conditions. Latin America and the Caribbean have been most affected by this outbreak ( Figure 1 ). Since February 2016, new cases in the southern parts of the region have decreased, but an increase in new cases is expected in the Caribbean during the summer months as mosquitoes hatch and bite. The United States will likely experience an increase in travel-associated cases and possibly local transmission. Policymakers are concerned about the spread of Zika into the continental United States, as well as the potential that visitors traveling to the Olympics in Brazil in August could contract the virus and bring it back to their home countries. In February 2016, WHO Director-General Margaret Chan announced that the International Health Regulations (2005) Emergency Committee on Zika virus had determined that the Zika outbreak was a Public Health Emergency of International Concern (PHEIC). Shortly thereafter, President Barack Obama requested that Congress provide almost $1.9 billion in emergency appropriations to fund domestic and international responses to the outbreak. A conference agreement on Zika funding was approved by the House but remains pending in the Senate. As Congress considers funding the Zika request and then exercises oversight over U.S. Zika responses in Latin America and the Caribbean, Members may consider issues such as the following: Balance between U.S. bilateral and multilateral Zika responses . Although U.S. health assistance (bilateral and regional) to Latin America in general has declined, U.S. support for the Pan American Health Organization (PAHO) has increased. While considering the President's Zika request and the FY2017 budget request, Congress may discuss how much support to provide for multilateral responses in the region led by PAHO. U.S. health programs in Latin America as a part of U.S. policy toward the region . On average, roughly 10%-20% of the funds provided by the State Department and the U.S. Agency for International Development (USAID) for Latin America between FY2009 and FY2016 have been aimed at health programs. The WHO has recommended that women and men in countries with local transmission of Zika be correctly informed and oriented to consider delaying pregnancy. Congress may evaluate reproductive health and family planning funding in the region given the WHO recommendation and the limited access to sexual education and contraception in the region. Regional a pportionment and components of global health budget . Less than 5% of all U.S. global health funds are provided to Latin America, and the majority of these funds are for HIV/AIDS programs. On average, health indicators in the region—particularly those related to maternal and child health, family planning, and reproductive health—are better than in other low- and middle-income countries, although inequities exist. Congress might reexamine the apportionment of global health funding and consider whether investments in the region are sufficient to meet emerging health concerns. F unding for pandemic preparedness . The United States committed to support 30 countries (including Haiti and Peru) and the Caribbean Community (CARICOM) in bolstering their ability to respond to disease outbreaks through the Global Health Security Agenda (GHSA). Congress included almost $600 million in emergency Ebola appropriations to the CDC in support of GHSA and $50 million in FY2016 appropriations to USAID for pandemic preparedness activities. Congress might consider funding levels for those programs and where those funds are allotted. Investments in research and development of neglected diseases . In recent years, Aedes mosquitoes have caused three disease outbreaks (dengue, chikungunya, and Zika) in Latin America and the Caribbean, all of which have been imported into the United States, with the latter being only travel-associated at the time of this report. These and other diseases lack vaccines to prevent transmission, treatment regimens, and effective vector control tools. Congress might evaluate options to address threats from new and reemerging diseases, including those that are mosquito-borne. This report provides background information on the Zika virus, discusses challenges faced by governments and implementing partners in the Latin America and Caribbean region that are attempting to control the ongoing outbreak, and analyzes the above issues in the context of the U.S. Zika response. Zika was discovered in the Zika forest of Uganda in 1947. From that time until 2007, when the first large Zika outbreak was recorded, Zika virus infection primarily caused mild symptoms (fever, skin rash, conjunctivitis, muscle and joint pain) that resolved within one week. In 2007, the first large Zika outbreak was recorded on the Micronesian island of Yap. Household surveys detected 185 cases. Scientists are studying the virulence of the Zika virus and the extent to which human activity affects global spread. Retrospective studies of a 2013-2014 outbreak in French Polynesia linked Zika infection with GBS for the first time. The current outbreak, which began in Brazil, has been accompanied with a spike in microcephaly and GBS cases, as well as other neurological and autoimmune disorders. As of June 16, 2016, WHO has reported more than 1,600 cases of Zika-related microcephaly worldwide—almost all in Brazil. In addition, 13 Zika-affected countries have recorded an increased incidence of GBS. In the last century, Latin American and Caribbean countries have transformed from largely rural to mostly urban societies, with some 80% of all people in Latin America and the Caribbean now living in urban areas. Throughout the region, millions of people live in densely populated urban slums and poor rural communities where homes and other facilities lack air conditioning or window screens. Lack of proper plumbing and poor sanitation facilitate mosquito breeding, as mosquitoes can lay their eggs in standing water. Aedes mosquitoes thrive in such conditions, biting during the day and breeding indoors and out. Health threats to Latin American and Caribbean populations may also be exacerbated by the 2015-2016 El Niño weather pattern, which is reflected in unusually warm water in the eastern equatorial Pacific Ocean. The present El Niño phenomenon, which has been particularly strong, has produced multiyear droughts in some areas (Colombia, Venezuela, and northern Central America) and extreme flooding in others (Argentina, Uruguay, and Paraguay). The warm, wet weather has facilitated the proliferation of mosquitoes, and human responses to drought conditions have provided favorable conditions for mosquito breeding because more people have been storing water. Studies have also linked climate change with greater health threats, such as increasing prevalence of malaria, chikungunya, and dengue fever. In recent years, Aedes mosquitoes have spread chikungunya, dengue, and Zika across the Americas. All three of these diseases have been imported into the United States and can become locally transmissible because the Aedes mosquito resides in large segments of the United States. Scientists are unsure how many people have been infected by Zika in the Western Hemisphere, but as many as 4 million people may be at risk of infection, and nearly all countries have recorded cases. As of June 16, 2016, Brazil had 159,914 suspected Zika cases, almost 40,000 of which have been confirmed through diagnostic testing (see Figure 3 ). Since the outbreak began in Colombia, the country had recorded 82,935 suspected cases, more than 8,000 of which have been confirmed. Two key factors complicate efforts to count Zika cases: 1. About 75% of infected people do not develop symptoms. 2. The virus is detectable for less than seven days in infected people's blood. As of June 16, 2016, all Zika cases detected in the continental United States (755) had been either acquired abroad or sexually transmitted, although the U.S. Virgin Islands, American Samoa, and Puerto Rico have experienced local transmission by mosquito. CDC and other health experts are preparing for the likelihood that the continental United States may experience locally acquired Zika cases this summer. Given the broad range of the Aedes mosquitoes (see Figure 2 ) and the fact that mosquito-borne diseases have been imported into the United States previously, a successful response to the Zika outbreak may require U.S.-Latin American cooperation in surveillance, research, and response over several years. The number of Zika cases, the capacity of health systems to address them and related complications, and the plans to do so vary widely across Latin America and the Caribbean. Haiti, for example, lacks a functioning hospital system, and Venezuela has little capacity to provide basic maternal and child health care at this time. In terms of preparedness and response to epidemiological emergencies, including Zika, recent assessments of core capacities under the International Health Regulations carried out by PAHO have highlighted weaknesses in health system capacity in all Caribbean countries (including Suriname and Guyana), selected countries of Central America (El Salvador, Guatemala, Honduras, and Nicaragua), Bolivia, and Paraguay. The Inter-American Development Bank (IDB) shares this view. Experts are concerned that these countries and several others are much less equipped than Brazil and Colombia—two of the six countries in the Americas that PAHO deemed capable of handling a pandemic illness in 2012—to address Zika and related health consequences. Inadequate laboratory and diagnostic capacity, poor access to sexual education and contraception, and resistance to national mosquito control efforts due to mistrust of government authorities have hindered efforts in some countries. Gang violence and insecurity have also reportedly prevented health workers from providing services in some parts of El Salvador and Honduras.