Earlier it was Ebola virus that caught global attention and now it is Zika Virus. Zika has caused a worldwide concern for its notorious ability to affect growing fetuses in the womb leading to small head (microcephaly).

Viral diseases can be innocuous or deadly. In last several years, newer viruses have emerged, leading to endemics and epidemics.

Here is the chronology of Zika virus in last 70 years that it originated to the current disease spectrum:

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.

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 a week ago.

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 fetus.

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

SOURCES: World Health Organization, U.S. Centers for Disease Control and Prevention, Reuters

(Reporting by Ben Hirschler; Editing by the Americas Desk for Reuters)