Timeline: Zika's origin and global spread

Workers fogging in the housing estate at Aljunied Crescent in Singapore on Aug 28, 2016.
Workers fogging in the housing estate at Aljunied Crescent in Singapore on Aug 28, 2016.PHOTO: AFP

Cases of the Zika virus have been found in more than 50 countries so far. The following timeline charts the origin and spread of the 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.

2015

March 2: Brazil reports illness characterised by skin rash in north-eastern 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.

Nov 2015-Jan 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.

2016

Feb 1: World Health Organisation (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: US Centres for Disease Control and Prevention (CDC) says virus being actively transmitted in 30 countries, mostly in the Americas.

Feb 8: US President Barack Obama requests US$1.8 billion (S$2.45 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 US$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 from 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 Organisation, 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 CDC 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 14: Colombia confirms two microcephaly cases linked to Zinka.

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 19: The Chilean authorities find Zika mosquito for first time in decades.

April 25: Canada confirms first sexually transmitted Zika case.

April 26: Brazil says the number of confirmed cases of microcephaly climbed to 1,198 from 1,168 in the week through April 23, but suspected ones under investigation continued to decline to 3,710 from 3,741 the previous week.

Brazil registered 91,387 likely cases of the Zika virus from February until April 2, the Health Ministry said, in its first national report on the epidemic.

April 29: Puerto Rico reports first death related to Zika, according to the CDC. The country also confirmed 683 Zika cases, including 65 pregnant women, and five suspected cases of Guillain-Barre syndrome from Zika, the CDC reported.

May 4: Panama confirms four microcephaly cases tied to Zika.

May 6: Spain gets first case of Zika-related brain defect in a foetus.

May 9: CDC adds Papua New Guinea, Saint Barthelemy and Peru to countries and territories with active outbreaks, bringing total to 46.

Honduras suspects first case of microcephaly in Zika patient.

May 11: Brazil says the number of confirmed cases of microcephaly dropped to 1,326 in the week through May 7 as doctors and Brazilian health officials find that some suspected cases of microcephaly are not the disorder. Suspected ones under investigation continued to decline to 3,433.

May 12: CDC adds Grenada to countries and territories with active outbreaks, bringing total to 47.

May 13: Puerto Rico reports first case of Zika-related microcephaly.

May 20: WHO says an outbreak of Zika virus on the African island chain of Cape Verde is of the same strain as the one blamed for birth abnormalities in Brazil.

May 24: Brazil reports the number of confirmed cases of microcephaly at 1,434 for the latest week to May 21. Suspected ones under investigation declined to 3,257.

May 26: CDC adds Argentina to countries and territories with active outbreaks, bringing total to 48.

June 9: WHO issues updated guidelines on prevention of sexual transmission of the Zika virus, including advising women living in areas where the virus is being transmitted to delay getting pregnant.

June 14: El Salvador confirms first case of microcephaly linked to Zika.

June 23: CDC reports seven babies in the United States with microcephaly or other Zika-related birth defects such as serious brain abnormalities, and five lost pregnancies from either miscarriage, stillbirth or termination.

June 28: First baby with Zika-related birth defect microcephaly born in Florida.

June 30: CDC adds Anguilla to countries and territories with active outbreaks, bringing total to 49. Guinea-Bissau confirms three cases of Zika, government says. Spain records first case of sexually transmitted Zika virus.

July 8: CDC confirmed that a Utah resident's death last month is the first Zika-related death in the continental United States.

July 14: CDC adds Saint Eustatius to countries and territories with active outbreaks, bringing total to 50.

July 15: New York City's health department reports the first female-to-male transmission of the Zika virus.

July 18: CDC reports that caregiver of Utah man who died of Zika tested positive for virus.

July 19: Florida health officials are investigating a case of Zika virus infection that does not appear to have stemmed from travel to another region with an outbreak.

July 21: CDC reports 400 pregnant women in US with evidence of Zika infection, up from 346 a week ago. The health agency also reports three more babies born in US with birth defects linked to the Zika virus, bringing total to 12. Florida Department of Health said it was investigating a non travel-related case of Zika in Broward County, marking the second such case in the US

July 22: New York City health officials reports first baby born with Zika-related birth defect.

July 25: Spain reports first case in Europe of baby born with Zika-related defect. CDC issues updated recommendations for preventing and testing for Zika infection, warning that the virus can be transmitted through unprotected sex with an infected female partner.

July 26: Honduras detects 8 cases of babies with Zika-related defect. CDC adds Saba to countries and territories with active outbreaks, bringing total to 51.

July 27: Paraguay reports first cases of microcephaly linked to Zika.

July 29: Florida authorities report what is believed to be the first evidence of local Zika transmission in the continental United States.

Aug 1: Florida identifies 10 more cases of Zika virus caused by mosquitoes, bringing total to 14. CDC issues guidelines for pregnant women who live in and travelled to affected area in a Miami neighbourhood.

Aug 2: The health authorities in Florida add one more case of locally transmitted Zika, bringing total to 15. CDC adds Antigua, Barbuda, and Turks and Cacos to countries and territories with active outbreaks, bringing total to 54.

Aug 3: US researchers said they launched Zika vaccine clinical trial.

Aug 4: Cuba reports two cases of locally transmitted Zika.

Aug 5: The Florida health authorities report another locally transmitted case, bringing total to 16.

Aug 8: Florida said it was investigating new case of locally transmitted Zika in Palm Beach County.

Aug 9: Texas health officials said death of infant born with microcephaly is linked to Zika, the first casualty in the state associated with the virus. Cayman Islands reports two locally transmitted Zika cases. Florida announces four more cases of locally transmitted Zika, bringing total to 21.

Aug 11: Florida reports three additional cases of locally transmitted Zika, bringing total to 25. CDC adds Cayman Islands to countries and territories with active outbreaks, bringing total to 55.

Aug 12: Florida health officials said three more people test positive for locally-transmitted Zika, bringing total to 28. The department of Health and Human Services declares public health emergency in Puerto Rico over Zika with 10,690 laboratory-confirmed cases.

Aug 13: Brazil reports 1,835 confirmed cases of microcephaly.

Aug 15: Florida health officials said two more people test positive for locally-transmitted Zika, bringing total to 30.

Aug 16: Haiti reports first case of microcephaly linked to Zika.

Aug 17: Guatemala confirms first case of newborn with microcephaly linked to Zika.

Aug 18: Florida health officials find evidence of Zika transmissions in Miami Beach

Aug 19: Florida governor says five cases of Zika are believed to have been contracted in Miami Beach, the second area in Miami-Dade county where the virus is spreading. The Florida health department said there are 36 cases of likely local transmission in the state.

Aug 23: Florida reports five new non-travel cases, including one in Pinellas County. The total number of local transmissions in Florida is 42.

Aug 24: Florida reports non-travel related Zika case in Palm Beach County, bringing total of local transmissions to 43.

Aug 25: Hong Kong confirms its first case of Zika. CDC adds the Bahamas and the United States to countries and territories with active outbreaks, bringing total to 57. Health officials in Puerto Rico report as many as 10 people developed Guillain-Barre syndrome as a result of Zika infections.

Aug 26: FDA recommended that all blood donated in the United States and its territories be tested for Zika virus, starting with 11 states in the first phase. Florda health officials lower total number of locally-transmitted Zika cases to 42. Nicaragua confirms first microcephaly birth linked to Zika.

Aug 27: Singapore confirms first case of locally transmitted Zika virus.

SOURCES: WORLD HEALTH ORGANISATION, US CENTERS FOR DISEASE CONTROL AND PREVENTION, REUTERS