May 7: The Pan American Health Organization (PAHO) and the World Health Organization (WHO) issue a joint epidemiological alert on ZVI.46
July 15: Brazil confirms Zika virus circulation in that country. This is the first report of locally acquired ZVI in the Americas.17
July 17: Brazil reports the detection of neurological disorders associated with a history of ZVI. Forty-nine cases are confirmed as Guillain–Barré syndrome.3,47
October 31: Brazil reports an unusual increase in the number of cases of microcephaly among newborns since August, totaling 54 by October 30.3,48
November 3: Colombia reports 239 cases of locally acquired ZVI.49
November 11: Brazil reports 141 suspected cases of microcephaly. Officials declare a national public health emergency as cases of suspected microcephaly continue to increase.3,50
November 17: PAHO and WHO issue an epidemiological alert asking PAHO member states to report observed increases of congenital microcephaly and other central nervous system (CNS) malformations.51 Brazil’s Ministry of Health reports the detection of Zika virus in amniotic fluid samples from two pregnant women whose fetuses were confirmed by ultrasound examinations to have microcephaly.52
November 21: Brazil reports that 739 cases of microcephaly, including one fatal case, are being investigated in nine states.53
November 24: Authorities in French Polynesia hypothesize that ZVI may be linked to CNS malformations if mothers are infected during the first or second trimester of pregnancy.54 El Salvador reports its first RT-PCR–confirmed cases of locally acquired ZVI.55
November 26: Mexico reports three RT-PCR–confirmed cases of ZVI; two were locally acquired, and the third had traveled to Colombia.56
November 27: Venezuela57 and Paraguay58 report RT-PCR–confirmed cases of locally acquired ZVI.
November 28: Brazil detects the Zika virus genome in blood and tissue samples from an infant with microcephaly. Brazil also reports the Zika-associated deaths of two adults and one newborn.59
December 1: PAHO and WHO issue an alert on ZVI’s association with neurological syndromes and congenital malformations in the Americas. The alert includes guidelines for laboratory detection of the virus.60
December 6: Cabo Verde, a group of islands off the coast of western Africa, reports that it has 4,744 suspected cases of locally acquired ZVI. No neurological complications are observed.61
December 16: Honduras reports two RT-PCR–confirmed cases of locally acquired ZVI.62
December 17: Four ZVI cases are confirmed by RT-PCR in Panama.63
December 21: French Guiana and Martinique report their first RT-PCR–confirmed cases of locally acquired ZVI.64
December 22: Brazilian researchers publish evidence that the characterization of Zika virus as a “mild cousin of dengue” may not be accurate because of the possibility of more-serious disease symptoms, especially in immunocompromised patients.65
December 29: Brazil updates the number of suspected microcephalycases to 2,975.66
December 31: The Centers for Disease Control and Prevention (CDC) reports the first RT-PCR–confirmed case of locally acquired ZVI in the Commonwealth of Puerto Rico.67
January 4: Brazil reports 3,174 suspected cases of microcephaly, including 38 deaths.68
January 5: Researchers report the first diagnoses of intrauterine transmission of Zika virus in two pregnant women in Brazil whose fetuses were diagnosed with microcephaly. Although blood tests in both women are negative, Zika virus is detected in amniotic fluid.69
January 7: The Maldives report that a Finnish national who worked in the country became ill upon his return to Finland, where he tested positive for ZVI on RT-PCR.70 Scientists find that Zika virus strains in four patients in Suriname belong to the Asian genotype and are almost identical to the strain that circulated in French Polynesia in 2013.71 Ophthalmologists in Brazil report severe ocular malformations in three infants born with microcephaly.72
January 12: In collaboration with health officials in Brazil, the CDC releases laboratory findings from four microcephaly cases in Brazil. The findings indicate the presence of Zika virus in brain tissue from two newborns. In addition, the placenta of two fetuses miscarried during the first 12 weeks of pregnancy test positive by RT-PCR. The findings are considered the strongest evidence to date of an association between ZVI and microcephaly.73
January 14: Guyana reports its first RT-PCR–confirmed case of locally acquired ZVI.74
January 15: The CDC issues interim travel guidance for pregnant women, advising those in any trimester to consider postponing travel to areas with ongoing local transmission of Zika virus or to take precautions against mosquito bites if they must travel.75 Barbados reports its first RT-PCR–confirmed case of locally acquired ZVI.74 A case of microcephaly is reported in Hawaii in the infant of a woman who had resided in Brazil early in her pregnancy.76
January 16: The Plurinational State of Bolivia reports its first RT-PCR–confirmed case of locally acquired ZVI. Panama confirms six cases of ZVI; two were locally acquired, three were imported from Columbia, and one was from the Bolivarian Republic of Venezuela.3,77
January 18: Haiti reports its first RT-PCR–confirmed cases of locally acquired ZVI.77
January 19: El Salvador reports an unusual increase in cases of Guillain–Barré syndrome.78
January 21: Brazil reports 3,893 suspected cases of microcephaly, including 49 deaths.77
January 22: Brazil reports that 1,708 cases of Guillain–Barré syndrome have been registered by hospitals.79
January 23: The Dominican Republic reports its first RT-PCR–confirmed cases of ZVI; eight were locally acquired and two were imported from El Salvador.77
January 25: The CDC reports the first RT-PCR–confirmed case of locally acquired ZVI on the island of St. Croix in the U.S. Virgin Islands.80 France reports two confirmed cases of Guillain–Barré syndrome in Martinique; one of the patients tests positive for ZVI.77
January 26: The CDC issues treatment guidelines for infants exposed to Zika virus.81 A Virginia resident who had traveled abroad tests positive for ZVI.82
January 27: The White House announces that most of its efforts to fight the Zika virus will focus on sharing information about the risks with the public.83
January 29: Officials in Brazil report that infants with microcephaly also have serious eye damage.84 Suriname reports 1,107 suspected cases of ZVI; 308 are confirmed by RT-PCR.77
January 30: Jamaica reports its first RT-PCR–confirmed case of locally acquired ZVI.85
February 1: Brazil’s top health official tells Reuters that the Zika virus outbreak is worse than believed because most cases show no symptoms.86 WHO announces that the recent association of ZVI with microcephaly and other neurological disorders constitutes a Public Health Emergency of International Concern.87 New York City offers free Zika tests for people with symptoms of ZVI.88
February 2: Texas reports a case of sexual transmission of ZVI. The patient had not recently travelled outside the U.S., but developed symptoms after sexual contact with a traveler. This is the first U.S. Zika case in someone who had not traveled abroad, and the third indication that the virus can be sexually transmitted.27,89 A Brazilian official says pregnant women should not travel to that country for the Olympic Games in August.90 Chile announces its first RT-PCR–confirmed cases of ZVI on the mainland in travelers returning from Colombia, the Bolivarian Republic of Venezuela, and Brazil.87 Two ZVI cases are reported in Australia; both individuals had visited Haiti.91
February 3: The CDC puts its emergency operations center on the highest level of activation to respond to the Zika outbreak.92 The WHO calls for further investigation into the sexual spread of ZVI.93
February 4: Brazilian health officials confirm a case of ZVI transmitted by transfused blood from an infected donor.87 The United Kingdom announces plans to spray insecticide inside planes from Zika-affected countries.94
February 5: Brazilian health officials say they have found live Zika virus in the urine and saliva of infected people.95 The CDC recommends that men who have recently returned from areas with Zika virus use condoms during sexual intercourse, especially with a pregnant partner, to prevent virus transmission.96 Puerto Rico’s governor declares a public health emergency because of the Zika virus.97
February 7: Suriname reports an increase in cases of Guillain–Barré syndrome; 10 cases are confirmed to be positive for Zika virus by RT-PCR urine tests.87 France announces that travelers returning from any outbreak zones of the Zika virus will have to wait at least four weeks before giving blood to avoid the risk of transmission.98
February 8: The Obama administration asks Congress for $1.8 billion to fight the Zika outbreak.99 The U.S. Olympic Committee tells sports federations that athletes and staff concerned for their health should consider not going to the Olympics in Rio de Janeiro in August.100
February 10: Colombia reports that nearly 100 people with Guillain–Barré syndrome also have Zika symptoms.87 China confirms its first case of ZVI in a man in Jiangxi province.101 Finland reports two cases of ZVI; one subject had returned from a vacation in the Maldives.102
February 12: The National Institute of Allergy and Infectious Diseases announces that the Zika virus may “hide” in parts of the body that are shielded from the immune system, making it harder to fight.103 In England, Zika virus is found in the semen of a man two months after he was first infected, suggesting that the virus may linger in semen long after symptoms of the infection fade.104
February 13: The WHO announces that Guillain–Barré syndrome is on the rise in five Latin American countries (Brazil, Colombia, El Salvador, Suriname, and Venezuela), but with no proven link to ZVI.105 Colombia reports that more than 5,000 pregnant women have ZVI.106
February 15: Russia reports its first case of ZVI after a tourist contracted the disease in the Dominican Republic.107
February 16: The FDA recommends the deferral of individuals from donating blood if they have been to areas with active Zika virus transmission, potentially have been exposed to the virus, or have had confirmed ZVI.23 Mexico confirms that six pregnant women are infected with Zika virus, bringing the total number of cases to 80.108
February 17: Researchers in Rio de Janeiro report that Zika virus can cross the placental barrier.109 Brazilian government officials say “most” of the country’s confirmed microcephaly cases are linked to ZVI.110
February 18: The World Bank makes $150 million in financing available to help fight Zika in affected Latin American and Caribbean countries.111
February 19: The CDC issues updated guidelines for health care providers caring for infants or children with possible ZVI.112
February 20: South Africa reports its first case of confirmed ZVI in a Colombian man.113
February 22: Cuba deploys 9,000 troops in an effort to avoid the Zika virus by eradicating mosquitoes.114
February 23: The CDC reports that it is investigating 14 new reports of possible sexual transmission of Zika virus, including several involving pregnant women. The agency says sexual transmission may be a “more likely” means of transmission for the virus than previously thought.115 In Texas, two hospitals announce that they have developed a rapid RNA test for Zika virus.116
February 24: The Czech Republic reports its first cases of ZVI.117 Colombia announces a “probable” case of microcephaly in an aborted fetus. Zika virus was identified in the mother’s amniotic fluid.118
February 25: A Yale School of Public Health researcher reports that, in addition to microcephaly, ZVI may cause hydrops fetalis (the abnormal accumulation of fluid in fetal compartments), hydranencephaly (the almost complete loss of brain tissue), and fetal demise (stillbirth).119,120
February 26: The FDA authorizes a new CDC laboratory test for ZVI for emergency use. The Zika IgM Antibody Capture Enzyme-Linked Immunosorbent Assay (Zika MAC-ELISA) is intended for use in detecting antibodies in blood samples from people with a history of symptoms associated with ZVI and/or people who have recently traveled to an area during a time of active Zika virus transmission.121
February 27: France reports Europe’s first sexually transmitted ZVI case. A woman was infected after her partner returned from Brazil.122
February 28: French scientists confirm a link between ZVI and Guillain–Barré syndrome in the 2013–2014 Polynesian outbreak. The risk of developing Guillain–Barré is calculated at 24 people for every 100,000 infected by the virus.123
March 1: The FDA issues new guidelines aimed at preventing Zika virus transmission via human cell and tissue products.124 Cuba reports its first case of ZVI; the patient is a female doctor from Venezuela whose husband had contracted the virus in their home country.125
March 2: New Zealand’s health ministry announces that it is investigating whether the Zika virus was sexually transmitted from a man to his female partner. The man had tested positive for Zika after he visited an unnamed country.126
March 3: Google reports that its engineers are working with the United Nations Children’s Emergency Fund (UNICEF) to analyze data in an effort to map and anticipate the global spread of Zika virus.127 French researchers link ZVI to the paralyzing disorder myelitis in a 15-year-old girl in Guadeloupe. The presence of Zika virus in the girl’s cerebrospinal fluid suggests that the virus might be neurotropic.128
March 4: The White House and the CDC announce plans to gather state and local officials on April 1 to urgently craft a plan to attack the Zika virus. Federal health officials say they expect the first locally transmitted cases of ZVI in the continental U.S. by June or July.129 The WHO reports that there is “accumulating evidence” linking ZVI to microcephaly and Guillain–Barré syndrome.130 Scientists in Brazil discover that a mosquito more common than the one primarily known to transmit Zika may be able to carry the virus. Ae. aegypti is recognized as the main transmitter of ZVIs, but the scientists were able to infect another species, Culex quinquefasciatus, with the virus in a laboratory. Outside Brazil, C. quinquefasciatus exists in more-temperate climates, including the southern U.S., where it is known to carry the West Nile virus and can survive the winters.131
March 9: The WHO warns that mosquito spraying may not stop the spread of Zika virus. The agency also says that vaccine trials may come too late for the current outbreak.132 The CDC’s director calls Zika in Puerto Rico a “challenge and crisis.”133 Brazil announces that the number of microcephaly cases linked to ZVI has risen to 4,976.134
