Zika virus (ZIKV) is a member of the Flaviviridae virus family and the Flavivirus genus.
In humans, it causes a mild illness known as Zika fever, Zika, or Zika disease, which since the 1950s has been known to occur within a narrow equatorial belt from Africa to Asia. In 2014, the virus spread eastward across the Pacific Ocean to French Polynesia, then to Easter Island and in 2015 to Central America, the Caribbean, and South America, where the Zika outbreak has reached pandemic levels. Zika virus is related to dengue, yellow fever, Japanese encephalitis, and West Nile viruses, all of which are arthropod-borne flaviviruses. The illness it causes is similar to a mild form of dengue fever, is treated by rest, and cannot be prevented by drugs or vaccines.[3] There is a possible link between Zika fever and microcephaly in newborn babies of infected mothers.
In January 2016, the U.S. Centers for Disease Control and Prevention (CDC) issued travel guidance on affected countries, including the use of enhanced precautions and considering postponing travel, and guidelines for pregnant women. Other governments or health agencies soon issued similar travel warnings, while Colombia, Ecuador, El Salvador, and Jamaica advised women to postpone getting pregnant until more is known about the risks.
Transmission
Aedes aegypti - a mosquito vector of Zika virus
Zika virus is transmitted by daytime-active mosquitoes and has been isolated from a number of species in the genus Aedes, such as A. aegypti, and 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. The vertebrate hosts of the virus are primarily monkeys and humans. Before the current pandemic, which began in 2007, Zika virus "rarely caused recognized 'spillover' infections in humans, even in highly enzootic areas".
The potential societal risk of Zika virus can be delimited by the distribution of the mosquito species that transmit it (its vectors). The global distribution of the most cited carrier of Zika virus, A. aegypti, is expanding due to global trade and travel. A. aegypti distribution is now the most extensive ever recorded – across all continents including North America and even the European periphery.
Recent news reports have drawn attention to the spread of Zika in Latin America and the Caribbean. 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, Guatemala, Guadeloupe, Guyana, Haiti, Honduras, Martinique, Mexico, Panama, Paraguay, Puerto Rico, Saint Martin, Suriname, and Venezuela.
In 2009 Brian Foy, a biologist from the Arthropod-borne and Infectious Diseases Laboratory at Colorado State University, sexually transmitted Zika virus to his wife. 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 with Zika, but not before having had unprotected intercourse with his wife. She subsequently showed symptoms of Zika infection with extreme sensitivity to light. Foy is the first person known to have passed on an insect-borne virus to another human by sexual contact.
In 2015, Zika virus RNA was detected in the amniotic fluid of two fetuses, indicating that it had crossed the placenta and could cause fetal infection. On 20 January 2016, scientists from the state of Paraná, Brazil, detected genetic material of Zika virus in the placenta of a woman who had undergone an abortion due to the fetus's microcephaly, which confirmed that the virus is able to pass the placenta.
