The history of the Zika virus

The virus is recovered from the mosquito Aedes (Stegomyia) africanus, caught on a tree platform in the Zika forest.

The first human cases of virus infection are detected in Uganda and the United Republic of Tanzania.

Brazil is declared free of Aedes aegypti (the main vector for dengue, yellow fever, chikungunya and Zika) following an extensive eradication programme using DDT to control a yellow fever outbreak.

Two more Zika virus strains are isolated from Aedes africanus mosquitoes in the Zika forest area.

Zika detected in mosquitoes and test rhesus monkeys in a narrow band of countries that stretch across equatorial Africa. The virus is isolated from more than 20 mosquito species, mainly in the genus Aedes. Studies indicate widespread human exposure to the virus but the disease is regarded as benign.

The known geographical distribution of Zika expands to equatorial Asia, including India, Indonesia, Malaysia and Pakistan, where the virus is detected in mosquitoes and in the human population.

The first large outbreak of Zika in humans on the Pacific island of Yap, in the Federated States of Micronesia. Prior to this event only 14 cases of human Zika virus disease had been documented worldwide. An estimated 73% of Yap residents over three years of age were infected with Zika virus. No deaths, hospitalizations, or neurological complications are reported.

Analysis of Zika virus strains collected in Cambodia, Malaysia, Nigeria, Senegal, Thailand and Uganda, show two geographically distinct lineages of the virus in Africa and Asia. The outbreak on Yap Island was confirmed to have originated in South East Asia.

First evidence Zika may be sexually transmitted. On Tahiti in French Polynesia a patient recovering from Zika seeks reports having bloody semen, which is found to contain Zika virus.

First evidence of transmission of Zika from mother to foetus. In French Polynesia, two mothers and their newborns are found to have Zika virus infection. The babies’ infections appear to have been acquired during pregnancy or during delivery.

Brazil notifies WHO of outbreak of unknown illness characterized by skin rash with or without fever in north eastern states — 13% tested positive for dengue.

Brazil reports neurological disorders associated with patients having infection of Zika, chikungunya or dengue. 49 cases confirmed as Guillain-Barré syndrome.

Zika reported in Republic of Cabo Verde and Columbia.

Brazil reports 54 cases of microcephaly among newborns.

Brazil declares a national public health emergency.

The United States reports the first locally acquired Zika infection, in the Commonwealth of Puerto Rico.

The first diagnoses of intrauterine transmission of the Zika virus in two pregnant women in Brazil whose foetuses were diagnosed with microcephaly. Zika virus is detected in amniotic fluid even though the mothers tested negative.

Ophthalmologists in Brazil report severe eye malformations in three infants born with microcephaly.

WHO declares a Public Health Emergency of International Concern due to the association of Zika infection with microcephaly and other neurological disorders.

21 July: The Oswaldo Cruz Foundation in Brazil reported it had detected the Zika virus in Culex quinquefasciatus mosquitoes collected in Pernambuco State.

26 July: Inovio Pharmaceuticals and GeneOne Life Science announced the dosing of the first subject in its multi-center phase I trial to evaluate Inovio’s Zika DNA vaccine (GLS-5700).

29 July: US reported the first cases of mosquito-borne virus transmission of Zika, in Florida.

WHO declared an end to Public Health Emergency of International Concern (PHEIC) for microcephaly, other neurological disorders and Zika virus. The WHO Emergency Committee recommended that the Zika programme should be escalated into a sustained programme of work.

65 countries had reported an outbreak or possible transmission in 2015 and 2016.

WHO reports that more than 40 vaccine candidates are being developed and 5 are entering phase I clinical trials. Registration of first generation vaccines is expected in 2-3 years.