History

Virus isolation in monkeys and mosquitoes, 1947

The virus was first isolated in April 1947 from a rhesus macaque monkey that had been placed in a cage in the Zika Forest of Uganda, near Lake Victoria, by the scientists of the Yellow Fever Research Institute. A second isolation from the mosquito A. africanus followed at the same site in January 1948.^[44]
When the monkey developed a fever, researchers isolated from its serum a transmissible agent that was first described as Zika virus in 1952.

First evidence of human infection, 1952

Zika virus had been known to infect humans from the results of serological surveys in Uganda and Nigeria. A serosurvey of 84 people of all ages showed 50 had antibodies, all above 40 years of age were immune.

It was not until 1954 that the successful isolation of Zika virus from a human was published. This came as part of a 1952 outbreak investigation of jaundice suspected to be yellow fever; It was found in the blood of a 10 year old Nigerian female with low grade fever, headache and evidence of malaria, but no jaundice, who recovered within 3 days. Blood was injected into the brain of laboratory mice, followed by up to 15 mice passages. The virus from mouse brains was then tested in neutralization tests using rhesusmonkey sera specifically immune to Zika virus. In contrast no virus was isolated from the blood of two infected adults with fever, jaundice, cough, diffuse joint pains in one and fever, headache, pain behind the eyes and in the joints.

Infection was proven by a rise in Zika virus specific serum antibodies.^[45] A 1952 research study conducted in India had shown a "significant number" of Indians tested for Zika had exhibited an immune response to the virus, suggesting it had long been widespread within human populations.

Spread from equatorial Africa to Asia, 1951-1981

From 1951 through 1981, evidence of human infection with Zika virus was reported from other African countries, such as the Central African Republic, Egypt, Gabon, Sierra Leone, Tanzania, and Uganda, as well as in parts of Asia including India, Indonesia, Malaysia, the Philippines, Thailand, and Vietnam.^[23] From its discovery until 2007, confirmed cases of Zika virus infection from Africa and Southeast Asia were rare.

Micronesia, 2007

In April 2007, the first outbreak outside of Africa and Asia occurred on the island of Yap in the Federated States of Micronesia, characterized by rash, conjunctivitis, and arthralgia, which was initially thought to be dengue, chikungunya or Ross River disease.^[48] Serum samples from patients in the acute phase of illness contained RNA of Zika virus. There were 49 confirmed cases, 59 unconfirmed cases, no hospitalizations, and no deaths.^[49] More recently, epidemics have occurred in Polynesia, Easter Island, the Cook Islands and New Caledonia.

Americas, 2015-present

Main article: Zika virus outbreak in the Americas (2015–present)

Since April 2015, a large, ongoing outbreak of Zika virus that began in Brazil has spread to much of South and Central America, and the Caribbean. In January 2016, the U.S. CDC issued a level 2 travel alert for people traveling to regions and certain countries where Zika virus transmission is ongoing.^[50] The agency also suggested that women thinking about becoming pregnant should consult with their physicians before traveling.^[51] Governments or health agencies of the United Kingdom,^[11] Ireland,^[12] New Zealand,^[52] Canada,^[13] and the European Union^[13] soon issued similar travel warnings. In Colombia, Minister of Health and Social Protection Alejandro Gaviria Uribe recommended to avoid pregnancy for eight months, while the countries of Ecuador, El Salvador, and Jamaica have issued similar warnings.^[12][14]
Plans were announced by the authorities in Rio de Janeiro, Brazil, to try to prevent the spread of the Zika virus during the 2016 Summer Olympic Games in that city.

According to the CDC, Brazilian health authorities reported more than 3,500 microcephaly cases between October 2015 and January 2016. Some of the affected infants have had a severe type of microcephaly and some have died. The full spectrum of outcomes that might be associated with infection during pregnancy and the factors that might increase risk to the fetus are not yet fully understood. More studies are planned to learn more about the risks of Zika virus infection during pregnancy.^[53] In the worst affected region of Brazil, approximately 1 percent of newborns are suspected of being microcephalic.