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Where Did Zika Come From?

By Matt Longman | 09/17/2016
The Zika virus outbreak has been named a “public health emergency of international concern”1 by the World Health Organization (WHO). For most of the 20th century, the Zika virus was largely unknown. But the recent outbreak, rapid spread through several continents, and the virus’ potential links to infant microcephaly and temporary paralysis, has put the world is on high alert.

Scientists are researching to learn more about how the Zika virus works, and what we can do to treat and potentially cure it. As a result, what we know about Zika is changing very quickly. Here’s a brief history of the world’s findings so far, with information from the WHO.2


The Zika virus is discovered in a captive monkey, during a routine surveillance for yellow fever in Uganda’s Zika forest.


Researchers identify the first Zika cases in humans, detected in Uganda and the United Republic of Tanzania.


The Zika virus is proven to cause human disease. David Simpson was working with Zika strains in Uganda when he fell ill from the virus and published a study on his observations of the infection.

Throughout the next few decades, the virus was also detected in mosquitoes in India, Indonesia, Malaysia, and Pakistan. Only about 14 human cases of the disease were confirmed during this time frame.


The first large Zika outbreak is reported on the island of Yap, located in the Caroline Islands. Researchers believe the outbreak was spread overseas via infected air travelers.


The virus appears in French Polynesia, Easter Island, the Cook Islands, and New Caledonia. Researchers identify a possible link between the virus and microcephaly, autoimmune problems, and Guillain-Barré syndrome (temporary paralysis).

May 2015

7,000 cases of Zika are confirmed in Brazil. This is the first time it was transmitted locally in the Americas. Previously, it had only been present locally in Africa, Asia, and the Pacific islands.

October 2015

Colombia becomes the first country in the Americas outside of Brazil to report a locally acquired Zika infection. The country later confirmed 156 cases. Later that month, Brazil reported a sudden surge in microcephaly in infants3 — a congenital disorder in which a baby is born with an underdeveloped brain and an abnormally small head. Confirmations of the virus in Mexico, Guatemala, Paraguay, and Venezuela soon followed.

December 2015

By the end of December, Brazil reports nearly 3,000 cases of microcephaly. Most of them were reported in northeast Brazil, where the outbreak had originated.

January 2016

Puerto Rico reports its first case of Zika virus — the closest transmission had gotten to U.S. territories. The CDC began working on travel guidelines4 and warnings for pregnant women. Health workers confirmed that over 2,100 pregnant Colombian women were infected with the virus.

February 2016

The U.S. reports a case of Zika infection in Texas in someone who had traveled in Venezuela. They were later found to have sexually transmitted the disease to another person in the U.S. This was the first confirmation that Zika can be transmitted sexually,5 as well as by mosquito bites and through mother-to-fetus transmission.

April 2016

The WHO announces6 that Zika virus causes microcephaly and Guillain-Barré syndrome. Before this, they were unable to make any conclusions due to a lack of scientific evidence.

While it’s not entirely clear when the viral outbreak started, researchers believe that the virus may have come to Brazil during major sporting events that brought tens to hundreds of thousands of international travelers together in close proximity.

The current Zika virus outbreak in Brazil is a significant public health concern, especially given the recent Olympics in Brazil. If travelers to Brazil were infected and then brought the virus back to areas where the mosquito species is established, that could raise the possibility of local transmission of the virus.