Potential for mosquitoes in the United States to transmit Zika virus

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Zika virus is a mosquito-borne flavivirus first isolated in the Zika forest of what is now Uganda. For many decades, Zika virus was of no major epidemiological concern, causing occasional small outbreaks in Africa and Southeast Asia with only a handful of human cases recorded. This changed in 2007, when the first outbreak outside of Africa or Asia occurred on the island of Yap in Micronesia with approximately 100-200 confirmed or suspected cases. Zika virus is no longer a mild infection limited to Africa and Asia – it has now been introduced to the western hemisphere, with autochthonous Zika transmission documented in Brazil since May 2015, in other countries in central and south America, and over 250 imported cases in the United States (as of March 2016). Due to newly observed associations with major birth defects, the World Health Organization has declared Zika a global emergency and is estimating approximately 3-4 million cases by the end of 2016. Similar to dengue and Chikungunya viruses, the mosquito Aedes aegypti is thought to be the primary vector for Zika virus. Aedes albopictus has also been demonstrated to be a highly competent vector in laboratory studies. However, Zika virus has been detected in over 25 species of mosquitoes from 5 genera. Although detecting virus in a mosquito is not proof of transmission, these studies emphasize our lack of knowledge about the transmission biology of this emergent pathogen. Some identified vector species (Aedes albopictus and Aedes aegypti) are present in the United States and these vectors alone open the possibility of outbreaks and even local transmission in parts of the USA. If other native or established mosquito species are competent to transmit Zika, the virus could potentially move into the USA beyond areas currently colonized by aegypti and albopictus, similar to what was observed with the mosquito Culex tarsalis and the invasion of West Nile virus into the USA during the early 2000's. In this proposal, we will (1) investigate the potential for common, widespread mosquito species present in the United States to transmit Zika virus and (2) investigate geographic variation among Aedes albopictus populations to transmit Zika virus. Proactive knowledge about the potential role that North American mosquito fauna may play in the introduced epidemiology of Zika virus is absolutely critical for the development of efficient Zika virus control strategies and risk management policies in the USA.