As of early 2016, a widespread outbreak of Zika fever, caused by the Zika virus, is ongoing, primarily in the Americas. The outbreak began in April 2015 in Brazil, and has spread to other countries in South America, Central America, Mexico, and the Caribbean. In January 2016, the World Health Organization (WHO) said the virus was likely to spread throughout most of the Americas by the end of the year;[2] and in February 2016, the WHO declared the cluster of microcephaly and Guillain–Barré syndrome (GBS) cases reported in Brazil – strongly suspected to be associated with the Zika virus outbreak – a Public Health Emergency of International Concern.[3][4][5][6]
The virus is spread mainly by the Aedes aegypti mosquito, which is commonly found throughout the tropical and subtropical Americas. It can also be spread by the Aedes albopictus ("Asian tiger") mosquito, which has become widespread as far north as the Great Lakes region in North America.[7] Sexual transmission of the Zika virus is also possible.[6][8][9][10] Most Zika virus infections are asymptomatic, rendering precise estimates of the number of cases difficult to determine.[11] In approximately one in five cases, Zika virus infections result in Zika fever, a minor illness that causes symptoms such as fever and a rash. Critically, Zika virus infections of pregnant women have a suspected link with newborn microcephaly by mother-to-child transmission.[12][13] In addition, Zika is suspected of being associated with a cluster of cases of Guillain–Barré syndrome.[3]
A number of countries have issued travel warnings, and the outbreak is expected to significantly impact the tourism industry.[6][14] Several countries have taken the unusual step of advising their citizens to delay pregnancy until more is known about the virus and its impact on fetal development.[15]
As early as August 2014, physicians in Natal in northeatern
Brazil began to investigate an outbreak of illness characterized by a
flat pinkish rash, bloodshot eyes, fever, joint pain and headaches.[49] While the symptoms resembled dengue fever, testing ruled out this and several other potential causes.[49] By March 2015, the illness had spread to Salvador, Bahia and had appeared in three different states.[49] Then, in May 2015, researchers from the Federal University of Bahia determined, using the RT-PCR technique, that the illness was an outbreak of Zika virus.[50][51]
The Zika virus was first isolated in 1947, in a rhesus monkey in a forest near Entebbe, Uganda.[52] Although serologic evidence indicated additional human exposure during subsequent decades in parts of Africa and Asia,[53] before the 2007 Yap Islands Zika virus outbreak, only 14 cases of human Zika virus disease had been documented.[52]
Researchers generally believe the virus was brought to Brazil by an infected traveler who had been exposed to the virus in French Polynesia, who was then bitten by a mosquito that then infected others.[54][55][56] Phylogenetic analysis of the first Brazilian infections have strongly indicated that the circulating virus is the Asian, rather than African, strain of the virus, and was genetically similar to the virus found in the outbreak in French Polynesia.[54][56] It appears Zika's route – from Africa and Asia to Oceania and then the Americas – may mirror that of chikungunya and dengue, both of which are endemic in a large portion of the Americas.[57]
The precise event that brought the virus to Brazil is uncertain. Brazilian researchers have suggested that the Zika virus arrived during the 2014 FIFA World Cup tournament.[55] French researchers speculated the virus arrived shortly afterwards, in August 2014, when canoeing teams from French Polynesia, New Caledonia, Easter Island, and the Cook Islands, which had been or were experiencing Zika outbreaks, attended the Va'a World Sprint Championships in Rio de Janeiro.[49][54]
Confirmed cases have now been reported in most of South and Central America, and the Caribbean.[58] Cases have also been reported that were imported from South America into Europe,[59] Canada,[60] United States,[61] China,[62] and Australia.[63]
The virus is spread mainly by the Aedes aegypti mosquito, which is commonly found throughout the tropical and subtropical Americas. It can also be spread by the Aedes albopictus ("Asian tiger") mosquito, which has become widespread as far north as the Great Lakes region in North America.[7] Sexual transmission of the Zika virus is also possible.[6][8][9][10] Most Zika virus infections are asymptomatic, rendering precise estimates of the number of cases difficult to determine.[11] In approximately one in five cases, Zika virus infections result in Zika fever, a minor illness that causes symptoms such as fever and a rash. Critically, Zika virus infections of pregnant women have a suspected link with newborn microcephaly by mother-to-child transmission.[12][13] In addition, Zika is suspected of being associated with a cluster of cases of Guillain–Barré syndrome.[3]
A number of countries have issued travel warnings, and the outbreak is expected to significantly impact the tourism industry.[6][14] Several countries have taken the unusual step of advising their citizens to delay pregnancy until more is known about the virus and its impact on fetal development.[15]
Contents
Epidemiology
| [show]Country as of 3 March 2016 |
Autochthonous cases | Deaths | |
|---|---|---|---|
| [show]Country see ref. for latest update |
Autochthonous cases | |
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| [show]Country see ref. for latest update |
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The Zika virus was first isolated in 1947, in a rhesus monkey in a forest near Entebbe, Uganda.[52] Although serologic evidence indicated additional human exposure during subsequent decades in parts of Africa and Asia,[53] before the 2007 Yap Islands Zika virus outbreak, only 14 cases of human Zika virus disease had been documented.[52]
Researchers generally believe the virus was brought to Brazil by an infected traveler who had been exposed to the virus in French Polynesia, who was then bitten by a mosquito that then infected others.[54][55][56] Phylogenetic analysis of the first Brazilian infections have strongly indicated that the circulating virus is the Asian, rather than African, strain of the virus, and was genetically similar to the virus found in the outbreak in French Polynesia.[54][56] It appears Zika's route – from Africa and Asia to Oceania and then the Americas – may mirror that of chikungunya and dengue, both of which are endemic in a large portion of the Americas.[57]
The precise event that brought the virus to Brazil is uncertain. Brazilian researchers have suggested that the Zika virus arrived during the 2014 FIFA World Cup tournament.[55] French researchers speculated the virus arrived shortly afterwards, in August 2014, when canoeing teams from French Polynesia, New Caledonia, Easter Island, and the Cook Islands, which had been or were experiencing Zika outbreaks, attended the Va'a World Sprint Championships in Rio de Janeiro.[49][54]
Confirmed cases have now been reported in most of South and Central America, and the Caribbean.[58] Cases have also been reported that were imported from South America into Europe,[59] Canada,[60] United States,[61] China,[62] and Australia.[63]
