The Zika virus has gone from an obscure disease to an international public health emergency.
Researchers have been able to trace the gradual spread of Zika — slowly for decades and then, in the words of World Health Organization head Dr. Margaret Chan, “explosively” since 2015, when it was first detected in Brazil. Now the virus has reached more than 20 countries and territories in the Americas.
1947: FIRST IDENTIFIED
The virus was first identified in a rhesus monkey in the tropical Zika Forest in Uganda. The monkey was part of a study to identify viruses carried by mosquitoes. Researchers found that the monkey contracted a “hitherto unrecorded virus.”
1951 - 1981: AFRICA
Evidence of human infection was found in a number of countries in Africa, including Central African Republic, Egypt, Gabon, Nigeria, Sierra Leone, Tanzania and Uganda. As a rule, the number of cases over the decades was relatively small, but that could reflect the fact that symptoms are mild, nonexistent or mistaken for those of other viruses.
1951 - 1981: ASIA
Evidence of human infection was found in some Asian countries, including India, Indonesia, Malaysia, the Philippines, Thailand and Vietnam.
2007: YAP ISLAND
In April 2007, an outbreak began in Yap Island in the Pacific Ocean — the first detection of the virus outside the African and Asian continents and the first evidence that Zika could spread rapidly through a population.
2013-2014: PACIFIC ISLANDS
An outbreak occurred in the islands of French Polynesia, with an estimated 20,000 possible cases, and spread to other Pacific Islands: Cook Islands, Easter Island, New Caledonia, Solomon Islands and Vanuatu.
2015-2016: THE AMERICAS
The rough estimate of current cases in Brazil is 500,000 to 1.5 million, although it could be higher because many people who are infected show no symptoms.
These maps reflect data available from the CDC as of February 5. Due to space constraints, not all countries are labeled.
Source: Centers for Disease Control and Prevention, Pan American Health Organization
Credit: Alyson Hurt/NPR