Virology and Transmission (continued)

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The page below is a sample from the LabCE course Zika Virus: Overview and Laboratory Testing. Access the complete course and earn ASCLS P.A.C.E.-approved continuing education credits by subscribing online.

Learn more about Zika Virus: Overview and Laboratory Testing (online CE course)
Virology and Transmission (continued)

The first transmissions of the virus to vertebrate hosts were mainly in monkeys via mosquitoes, with only an occasional transmission to humans. In fact, before 2007, the Zika virus rarely caused human infections. Whereas other flaviviruses, such as yellow fever, chikungunya, and dengue viruses, had become established as human diseases spread by a mosquito to human cycle. In 2015, reports detailed the rapid spread of the Zika virus in Latin America and the Caribbean. As of August 2016, more than 50 countries had experienced local virus transmission. However, since 2018, Zika cases have been on the decline, and as of July 2022, there are no current outbreaks of Zika worldwide. In the U.S., the first Zika virus outbreak was in 2016, and cases spiked that year. However, cases in the U.S. have been on the decline since 2018. In 2021, the CDC reported 2 Zika virus cases (down 26 cases from 2019 and 72 cases from 2018) in travelers returning from affected areas. No cases were documented through local mosquito-borne transmission or through sexual transmission. In 2021 there were 32 Zika virus cases reported in the U. S Territories, with all of these cases acquired through local mosquito-borne transmissions. In 2022, getting the Zika virus in the U.S. is very rare because there is no current outbreak.
Typically, mosquitoes carrying the Zika virus will lay their eggs in and near standing water, such as buckets, bowls, flower pots, and vases. The mosquitoes prefer to live both indoors and outdoors near people where they can bite individuals, usually during the daytime. Mosquitoes usually become infected with the Zika virus when they feed on a person already infected with the virus, leading to the infected mosquito spreading to other people through their bites.
For a map of the Zika virus distribution in the U.S., please consult the CDC's case counts updated on Jan 13, 2023, available at the following link:
Zika Virus Case Counts in the U.S & Territories., CDC, updated April 10, 2023,

Aedes aegypti deposited eggs. Image courtesy CDC.