Zika fever

Zika virus
Aedes aegypti feeding on a human
Virus classification
Group:	Group IV ((+)ssRNA)
Family:	Flaviviridae
Genus:	Flavivirus
Species:	Zika virus

Zika fever is an illness caused by the Zika virus, a member of the family Flaviviridae. The fever and virus are named after the Ugandan forest where the virus was first isolated.

Epidemiology

The virus is commonly found in Africa but has also been found in Malaysia and Micronesia, including Yap Island from April to July, 2007. The very first known case of Zika fever was in a sentinel rhesus monkey stationed on a tree platform in the Zika Forest in Uganda in 1947. A few outbreaks have been reported in tropical Africa and in some areas in Southeast Asia. ^[1] The first major outbreak, with 185 confirmed cases, was reported in 2007 in the Yap Islands of the Federated States of Micronesia. This was also the first time Zika fever had been reported outside Africa and Asia. In 1978 a small outbreak of acute fever in Indonesia due to Zika virus infection was described.

The main clinical symptoms in patients are fever, conjunctivitis, transient arthritis/arthralgia (mainly in the smaller joints of the hands and feet) and maculo-papular rash that often starts on the face and then spreads throughout the body. In general the disease symptoms are mild and short-lasting (2-7 days). There is no evidence that Zika infection affects pregnant women or their babies. However, there are very few case reports in the literature. ^[2]

The most recent known outbreak has been reported on Yap Island, Federated States of Micronesia (FSM) from April to July 2007. This was the first outbreak of Zika virus identified outside of Africa and Asia. A total of 108 cases were confirmed by PCR or serology and 72 additional cases were suspected. The most common symptoms were rash, fever, arthralgia and conjunctivitis, and no deaths were reported. The mosquito Aedes hensilli, which was the predominant species identified in Yap during the outbreak, was probably the main vector of transmission. While the way of introduction of the virus on Yap Island remains uncertain, it is likely to have happened through introduction of infected mosquitoes or a viraemic human. ^[3]

Signs and symptoms

Symptoms are similar to Dengue fever, but are milder in form and usually last four to seven days. Hemorrhagic manifestations have been documented in only one instance, hematospermia (red–brown fluid in ejaculate).^[4] Common symptoms include a maculopapular skin rash that starts on the face or trunk before moving to the rest of the body, conjunctivitis, joint pain, low-grade fevers and headache.^[5]

Diagnosis

Zika virus can be identified by RT-PCR in acutely ill patients and from day 5 post onset of fever by serology through detection of specific IgM antibodies. Serological cross-reactions with closely related flaviviruses such as Dengue fever are possible. ^[6][7]

Reservoir

Zika virus is a mosquito-borne flavivirus closely related to dengue virus. The virus was first isolated in 1947 from a sentinel rhesus monkey stationed on a tree platform in the Zika forest, Uganda.

Transmission

Transmission is via the bite of Aedes aegypti mosquitoes. However there is an instance of human-to-human transmission thought to have been either by salvia or sexual transmission reported in April, 2011 by a university biologist bitten by mosquitoes while performing research in Senegal.

Prevention

It is generally believed that the virus is spread by mosquitoes, making vector control an essential element to disease control.

See also

• 2007 Yap Islands zika virus outbreak

References

External links

• Flaviviridae Genomes database search results from the Viral Bioinformatics Resource Center
• Viralzone: Flaviviridae
• Virus Pathogen Database and Analysis Resource (ViPR): Flaviviridae