The following timeline charts the origin and spread of the Zika virus from its discovery nearly 70 years ago:
1947: Scientists researching yellow fever in Uganda’s Zika Forest identify the virus in a rhesus monkey
1948: Virus recovered from Aedes africanus mosquito in Zika Forest
1952: First human cases detected in Uganda and Tanzania
1954: Virus found in Nigeria
1960s-80s: Zika detected in mosquitoes and monkeys across equatorial Africa
1969–83: Zika found in equatorial Asia, including India, Indonesia, Malaysia and Pakistan
2007: Zika spreads from Africa and Asia, first large outbreak on Pacific island of Yap
2012: Researchers identify two distinct lineages of the virus, African and Asian
2013–14: Zika outbreaks in French Polynesia, Easter Island, the Cook Islands and New Caledonia. Retrospective analysis shows possible link to birth defects and severe neurological complications in babies in French Polynesia
March 2, 2015: Brazil reports illness characterized by skin rash in northeastern states
July 17: Brazil reports detection of neurological disorders in newborns associated with history of infection
Oct. 5: Cape Verde has cases of illness with skin rash
Oct. 22: Colombia confirms cases of Zika
Oct. 30: Brazil reports increase in microcephaly, abnormally small heads, among newborns
Nov. 11: Brazil declares public health emergency
November 2015-January 2016: Cases reported in Suriname, Panama, El Salvador, Mexico, Guatemala, Paraguay, Venezuela, French Guiana, Martinique, Puerto Rico, Guyana, Ecuador, Barbados, Bolivia, Dominican Republic, Nicaragua, Curacao, Jamaica
Feb. 1: World Health Organization (WHO) declares public health emergency of international concern
Feb. 2: First case of Zika transmission in United States; local health officials say likely contracted through sex, not mosquito bite
Feb. 5: U.S. Centers for Disease Control and Prevention says virus being actively transmitted in 30 countries, mostly in the Americas
Feb. 8: U.S. President Barack Obama requests $1.8 billion to fight Zika
Feb. 12: Brazil investigating potential link between Zika infections and 4,314 suspected cases of microcephaly. Of those, 462 confirmed as microcephaly and 41 determined to be linked to virus
Feb. 17: Brazil investigating potential link between Zika and 4,443 suspected cases of microcephaly. Of those, 508 confirmed as microcephaly and most of those cases are linked to the virus. WHO seeks $56 million to fight Zika.
Feb. 18: CDC adds Aruba and Bonaire to countries and territories with active outbreaks, bringing total to 32.
Feb. 23: CDC investigating 14 cases of possible sexual transmission of Zika. CDC also adds Trinidad and Tobago and Marshall Islands to countries and territories with active outbreaks, bringing total to 34.
Feb. 25: Brazil says confirmed microcephaly cases number more than 580 and considers most of them to be related to Zika infections in the mothers. Brazil is investigating an additional 4,100 suspected cases of microcephaly.
Feb. 27: France detects first sexually transmitted case of Zika.
Feb. 29: CDC adds St. Maarten, and Saint Vincent and the Grenadines to countries and territories with active outbreaks, bringing total to 36.
March 1: Brazil says confirmed microcephaly cases rose to 641 and considers most of them to be related to Zika infections in the mothers. Brazil is investigating an additional 4,222 suspected cases of microcephaly.
March 8: WHO advises pregnant women to avoid areas with Zika outbreak and said sexual transmission of the virus is “relatively common.”
March 9: CDC adds New Caledonia to countries and territories with active outbreaks, bringing total to 37.
March 15: Cuba reports first case of Zika contracted in the country.
March 16: Cape Verde identifies first case of microcephaly.
March 18: CDC says during Jan. 1, 2015 to Feb. 26, 2016, 116 residents of the United States had evidence of recent zika virus infection based on laboratory testing.
Brazil says confirmed microcephaly cases rose to 863 and considers most of them to be related to Zika infections in the mothers. Brazil is investigating an additional 4,268 suspected cases of microcephaly.
March 19: CDC adds Cuba to countries and territories with active outbreaks, bringing total to 38.
March 21: South Korea confirms first case of Zika.
March 22: CDC adds Dominica to countries and territories with active outbreaks, bringing total to 39. Bangladesh confirms first case of Zika virus.
Brazil says confirmed microcephaly cases rose to 907 and considers most of them to be related to Zika infections in the mothers. Brazil is investigating an additional 4,293 suspected cases of microcephaly.
March 29: Brazil says confirmed microcephaly cases rose to 944 and considers most of them to be related to Zika infections in the mothers. Brazil said the number of suspected cases of microcephaly dropped slightly to 4,291.
March 31: According to the World Health Organization, there is a strong scientific consensus that Zika can cause the birth defect microcephaly as well as Guillain-Barre syndrome, a rare neurological disorder that can result in paralysis, though conclusive proof may take months or years.
April 1: CDC adds Kosrae, Federated States of Micronesia to countries and territories with active outbreaks, bringing total to 40.
April 4: CDC adds Fiji to countries and territories with active outbreaks, bringing total to 41.
April 5: Vietnam reports first Zika infections.
April 6: Brazil says confirmed microcephaly cases rose to 1,046 and considers most of them to be related to Zika infections in the mothers. The number of suspected cases of microcephaly dropped to 4,046.
April 7: St. Lucia confirms first two cases of Zika, contracted locally.
April 12: Brazil says confirmed microcephaly cases rose to 1,113 and considers most of them to be related to Zika infections in the mothers. The number of suspected cases of microcephaly dropped to 3,836. It was the second week in a row that the overall total figure fell.
April 13: The U.S. Centers for Disease Control and Prevention concluded that infection with the Zika virus in pregnant women is a cause of the birth defect microcephaly and other severe brain abnormalities in babies. The CDC said now that the causal relationship has been established, several important questions must still be answered with studies that could take years.
CDC adds St. Lucia to countries and territories with active outbreaks, bringing total to 42.
April 18: Peru reports first case of sexually transmitted Zika virus.
CDC adds Belize to countries and territories with active outbreaks, bringing total to 43.
April 25: Canada confirms first sexually transmitted Zika case.
SOURCES: World Health Organization, U.S. Centers for Disease Control and Prevention, Reuters
