Zika virus
| Zika virus | |
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| File:Aedes aegypti CDC-Gathany.jpg | |
| Aedes aegypti is a vector transmitting the Zika virus | |
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Group IV ((+)ssRNA)
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Zika virus
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Zika virus (ZIKV) is a member of the Flaviviridae virus family and the flavivirus genus, transmitted by Aedes mosquitoes. In humans, it causes a mild illness known as "zika" (pronounced zee-kuh), "Zika disease" or Zika fever, which was confined to Africa and Asia from the 1950's until 2007, when it emerged further East in Micronesia, South and Central America. The illness is related to dengue, yellow fever, West Nile disease, caused by other Flaviviruses, treated symptomatically and cannot be prevented by drugs or vaccines.
Virology
Along with other viruses in this family, Zika virus is enveloped and icosahedral with a non-segmented, single-stranded, positive sense RNA genome. It is most closely related to the Spondweni virus and is one of the two viruses in the Spondweni virus clade.[1][full citation needed] The virus was first isolated in 1947 from a rhesus monkey in the Zika Forest of Uganda, Africa, and was isolated for the first time from humans in 1968 in Nigeria.[2] From 1951 through 1981, evidence of human infection was reported from other African countries such as Uganda, Tanzania, Egypt, Central African Republic, Sierra Leone and Gabon, as well as in parts of Asia including India, Malaysia, the Philippines, Thailand, Vietnam and Indonesia.[2]
The pathogenesis of the virus is hypothesized to start with an infection of dendritic cells near the site of inoculation, followed by a spread to lymph nodes and the bloodstream.[1] Flaviviruses generally replicate in the cytoplasm, but Zika virus antigens have been found in infected cell nuclei.[citation needed]
Transmission
Zika virus is transmitted by daytime active mosquitoes and has been isolated from a number of species in the genus Aedes - Aedes aegypti, Aedes africanus, Aedes apicoargenteus, Aedes furcifer, Aedes hensilli, Aedes luteocephalus and Aedes vitattus. Studies show that the extrinsic incubation period in mosquitoes is about 10 days.[2] The vertebrate hosts of the virus include monkeys and humans.[citation needed]
Zika virus RNA was detected in the amniotic fluid of two fetuses, which indicates that it crossed the placental barrier, and that fetal infection is possible.[3]
In 2009, it was suggested that Zika virus can be sexually transmitted between humans. Brian Foy, a university biologist from the Colorado State University Arthropod-borne and Infectious Diseases Laboratory, visited Senegal to study mosquitoes and was bitten on a number of occasions during his research. A few days after returning to the United States he fell ill with Zika, but not before having unprotected intercourse with his wife. His wife subsequently showed symptoms of Zika infection, along 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.[4][5]
Clinical
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Common symptoms of infection with the virus include mild headaches, maculopapular rash, fever, malaise, conjunctivitis, and arthralgia. The first well documented case of Zika virus was described in 1964, began with a mild headache and progressed to a maculopapular rash, fever, and back pain. Within 2 days, the rash was fading, and within 3 days, the fever resolved and only the rash remained.[2] Thus far, Zica fever has been a relatively mild disease with limited scope, with only 1 in 5 persons developing symptoms, no fatalities, but its true potential as a virus and as an agent of disease is unknown.
As of 2016[update] no vaccine or preventive drug is available. Symptoms can be treated with acetaminophen or paracetamol, while aspirin and other non-steroidal anti-inflammatory drugs (NSAIDs) should only be used when dengue has been ruled out to reduce the risk of bleeding.[6]
Data suggest that newborns of mothers who had Zika virus infection during pregnancy are at an increased risk for microcephaly. It is suspected (but not proven) that a transplacental infection of the fetus may lead to microcephaly and brain damage.[7] In November 2015 Zika virus was isolated in a newborn from the northeastern state of Ceará, Brazil, with microcephaly and other congenital issues. In 2015 there were 2,782 cases of microcephaly compared with 147 in 2014 and 167 in 2013.[8][9][dead link] In December 2015 the European Centre for Disease Prevention and Control issued a comprehensive update on the possible association with congenital microcephaly and the association with Guillain–Barré syndrome.[10] The Lancet reported in January 2016 that the Brazilian Ministry of Health had only "confirmed 134 cases of microcephaly believed to be associated with Zika virus infection — a further 2165 cases in 549 counties in 20 states are under investigation".[11]
History
In 1947, scientists researching yellow fever placed a rhesus macaque in a cage in the Zika Forest (zika meaning "overgrown" in the Luganda language), near the East African Virus Research Institute in Entebbe, Uganda. The monkey developed a fever, and researchers isolated from its serum a transmissible agent that was first described as Zika virus in 1952. It was subsequently isolated from a human in Nigeria in 1954. From its discovery until 2007, confirmed cases of Zika virus infection from Africa and Southeast Asia were rare.[12]
In April 2007, the first outbreak outside of Africa and Asia occurred on the island of Yap in the Federated States of Micronesia, characterized by rash, conjunctivitis, and arthralgia, which was initially thought to be dengue, Chikungunya or Ross River disease.[13] However, serum samples from patients in the acute phase of illness contained RNA of Zika virus. There were 49 confirmed cases, 59 unconfirmed cases, no hospitalizations and no deaths.[14]
More recently, epidemics have occurred in Polynesia, Easter Island, the Cook Islands and New Caledonia.[12] Since April 2015, a large ongoing outbreak of Zika virus has occurred in Brazil. In the district of Camaçari and the neighbor city Salvador, capital of the state of Bahia, a previously unknown disease affecting around 500 patients with flu-like symptoms followed by rash and arthralgia was proven to be Zika fever, by researchers from Federal University of Bahia using RT-PCR technique.[15] Local authorities suspected the outbreak was due to an increased influx of foreign visitors attending the 2014 FIFA World Cup, coupled with the large population of Aedes aegypti and Aedes albopictus mosquitoes in the region. The spread followed a similar pattern to an outbreak of chikungunya virus in the same region, another disease previously unknown to the local population. French Polynesian researchers argued that none of the Pacific countries with circulating Zika participated in the soccer games and have suggested, that the outbreak is more likely linked to the Va'a World Sprint Championship canoe race in August, 2014. Besides Zika, a high incidence of the autoimmune disease Guillain–Barré syndrome was noted in French Polynesia and later in Brazil [11]
In December 2015, the Pan American Health Organization (PAHO) / World Health Organization (WHO) noted that transmission of Zika virus infection had occurred within nine countries: Brazil, Chile (specifically Easter Island), Colombia, El Salvador, Guatemala, Mexico, Paraguay, Suriname, and Venezuela.[16][17] PAHO/WHO made recommendations for surveillance, case management, and prevention.[16][17]
In December 2015 the first confirmed Zika virus case occurred in Puerto Rico. Besides cases in returning travelers, no other locally transmitted Zika cases have been reported from elsewhere in the United States.[18][19]
See also
References
This article contains public domain text from the CDC as cited
- ↑ 1.0 1.1 Fields Virology, 5th Edition
- ↑ 2.0 2.1 2.2 2.3 Lua error in package.lua at line 80: module 'strict' not found.
- ↑ Gretchen Vogel. Fast-spreading virus may cause severe birth defects Science Magazine American Association for the Advancement of Science. 3 December 2015, retrieved 7 January 2016
- ↑ Lua error in package.lua at line 80: module 'strict' not found.
- ↑ Lua error in package.lua at line 80: module 'strict' not found.
- ↑ Zika Virus For Health Care Providers: Clinical Evaluation & Disease CDC, June 1, 2015, retrieved January 8, 2016
- ↑ Lua error in package.lua at line 80: module 'strict' not found.
- ↑ Lua error in package.lua at line 80: module 'strict' not found.
- ↑ Folha de S.Paulo: In just one week, microcephaly cases increase 85% in Brazil.
- ↑ Lua error in package.lua at line 80: module 'strict' not found.
- ↑ 11.0 11.1 Lua error in package.lua at line 80: module 'strict' not found.
- ↑ 12.0 12.1 Lua error in package.lua at line 80: module 'strict' not found.
- ↑ Lua error in package.lua at line 80: module 'strict' not found.
- ↑ Lua error in package.lua at line 80: module 'strict' not found.
- ↑ http://g1.globo.com/bahia/noticia/2015/04/identificado-virus-causador-de-doenca-misteriosa-em-salvador-e-rms.html
- ↑ 16.0 16.1 Lua error in package.lua at line 80: module 'strict' not found.
- ↑ 17.0 17.1 Lua error in package.lua at line 80: module 'strict' not found.
- ↑ Zika virus CDC, 31 December 2015, accessed 7 January 2016
- ↑ Lua error in package.lua at line 80: module 'strict' not found.
