The vertebrate hosts of the virus were primarily monkeys in a so-called enzootic mosquito-monkey-mosquito cycle, with only occasional transmission to humans. Before the current pandemic
began in 2007, Zika virus "rarely caused recognized 'spillover'
infections in humans, even in highly enzootic areas". Infrequently,
other arboviruses
have become established as a human disease though, and spread in a
mosquito–human–mosquito cycle, like the yellow fever virus and the
dengue fever virus ( both flaviruses), and the chikungunya virus (a
togavirus).
Zika virus is transmitted by daytime-active mosquitoes as its vector and has been isolated from a number of species in the genus Aedes, such as A. aegypti, and in arboreal mosquitoes such as A. africanus, A. apicoargenteus, A. furcifer, A. hensilli, A. luteocephalus and A. vitattus. Studies show that the extrinsic incubation period in mosquitoes is about 10 days.[23] Transmission by Aedes albopictus,
the tiger mosquito, was reported from a 2007 urban outbreak in Gabon,
where it had newly invaded the country and become the primary vector for
the concomitant Chikungunya and dengue virus outbreaks.[24]
Since the first two cases of laboratory confirmed Zika virus infections
imported into Italy from French Polynesia were reported there is
concern for autochthonous infections in urban areas of European countries infested by Aedes albopictus from returning viremic travelers.
The potential societal risk of Zika virus can be delimited by the distribution of the mosquito species that transmit it . The global distribution of the most cited carrier of Zika virus, A. aegypti, is expanding due to global trade and travel.[26] A. aegypti distribution is now the most extensive ever recorded – across all continents including North America and even the European periphery.[27] A mosquito population capable of carrying the Zika virus has been found in a Capitol Hill neighborhood of Washington, D.C., and genetic evidence suggests they survived at least the last four winters in the region. The study authors conclude that mosquitos are adapting for persistence in a northern climate.
Since 2015 news reports have drawn attention to the spread of Zika in Latin America and the Caribbean.[29] The countries and territories that have been identified by the Pan American Health Organisation (PAHO) as having experienced "local Zika virus transmission" are Barbados, Bolivia, Brazil, Colombia, the Dominican Republic, Ecuador, El Salvador, French Guiana, Guadeloupe, Guatemala, Guyana, Haiti, Honduras, Martinique, Mexico, Panama, Paraguay, Puerto Rico, Saint Martin, Suriname, and Venezuela.[30][31]
Two reported cases suggest the Zika virus could be transmitted by sexual contact.[32] A biologist may have sexually transmitted Zika virus to his wife in 2009. He visited Senegal to study mosquitoes and was bitten on a number of occasions. A few days after returning to the United States, he fell ill, but not before having had unprotected intercourse with his wife. She subsequently showed some symptoms of Zika infection, and laboratory tests found Zika antibodies in both the biologist's and his wife's blood.[33][34] In early February, 2016, the Dallas County Health and Human Services department reported a case of Zika infection after sexual contact with an ill person.[35]
In 2015, Zika virus RNA was detected in the amniotic fluid of two fetuses, indicating that it had crossed the placenta and could cause a mother-to-child infection.[36] There is a possible link between Zika fever and microcephaly in newborn babies by mother-to-child transmission.
Vector
The potential societal risk of Zika virus can be delimited by the distribution of the mosquito species that transmit it . The global distribution of the most cited carrier of Zika virus, A. aegypti, is expanding due to global trade and travel.[26] A. aegypti distribution is now the most extensive ever recorded – across all continents including North America and even the European periphery.[27] A mosquito population capable of carrying the Zika virus has been found in a Capitol Hill neighborhood of Washington, D.C., and genetic evidence suggests they survived at least the last four winters in the region. The study authors conclude that mosquitos are adapting for persistence in a northern climate.
Since 2015 news reports have drawn attention to the spread of Zika in Latin America and the Caribbean.[29] The countries and territories that have been identified by the Pan American Health Organisation (PAHO) as having experienced "local Zika virus transmission" are Barbados, Bolivia, Brazil, Colombia, the Dominican Republic, Ecuador, El Salvador, French Guiana, Guadeloupe, Guatemala, Guyana, Haiti, Honduras, Martinique, Mexico, Panama, Paraguay, Puerto Rico, Saint Martin, Suriname, and Venezuela.[30][31]
Sexual
Two reported cases suggest the Zika virus could be transmitted by sexual contact.[32] A biologist may have sexually transmitted Zika virus to his wife in 2009. He visited Senegal to study mosquitoes and was bitten on a number of occasions. A few days after returning to the United States, he fell ill, but not before having had unprotected intercourse with his wife. She subsequently showed some symptoms of Zika infection, and laboratory tests found Zika antibodies in both the biologist's and his wife's blood.[33][34] In early February, 2016, the Dallas County Health and Human Services department reported a case of Zika infection after sexual contact with an ill person.[35]
During pregnancy
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