While researching yellow fever in 1947, scientists placed a rhesus monkey in a cage in the Zika Forest near the East African Virus Research Institute in Entebbe, Uganda. The monkey developed a fever, and researchers isolated from its serum a transmissible agent that was first described as the Zika virus in 1952. In 1954, the Zika virus was isolated from a human in Nigeria. After the discovery of the virus and until 2007, confirmed cases of Zika virus infection from Africa and Southeast Asia were rare. It was not until 2007 that a major epidemic of the Zika virus occurred in Yap Island, Micronesia. In 2015 and 2016, epidemics occurred in Polynesia, Easter Island, the Cook Islands, and New Caledonia.
During the Yap Island outbreaks of the virus, the condition was characterized by rash, conjunctivitis, and arthralgia (joint pain) and was initially believed to be dengue infection. When serum samples from patients in the acute phase of illness were analyzed, the results indicated that the samples contained RNA from the Zika virus. The Yap Island outbreak produced relatively mild symptoms of the Zika virus disease, with no deaths or hospitalizations reported.
A recent, larger outbreak of the Zika virus outside Africa occurred in April 2015 in Brazil. Healthcare authorities confirmed that approximately 500 patients who had flu-like symptoms, as well as a rash and arthralgia, had been infected with the Zika virus. Brazilian authorities linked that outbreak to an increased flow of foreign visitors attending the 2014 Fédération Internationale de Football Association (FIFA) World Cup, as well as the large population of insects (including
Aedes mosquitoes) that inhabit the region. Since 2015, a large, ongoing outbreak of the Zika virus has spread to much of South and Central America and the Caribbean. These outbreaks prompted the CDC to issue in early 2016 a level 2 travel alert for people traveling to regions and certain countries where Zika virus transmission is ongoing. Since Brazilian health authorities had reported a large number of microcephaly cases in infants, with some deaths occurring as a result of pregnant women having been infected with the Zika virus, the CDC also suggested that women thinking about becoming pregnant should consult with their physicians before traveling.
As previously indicated, in 2022, there are no current outbreaks of Zika virus in the U.S.
