Zika virus is an emerging mosquito-borne virus that was first identified in Uganda in 1947 in rhesus monkeys through a monitoring network of sylvatic yellow fever. It was subsequently identified in humans in 1952 in Uganda and the United Republic of Tanzania. Outbreaks of Zika virus disease have been recorded in Africa, the Americas, Asia and the Pacific.
- Genre: Flavivirus
- Vector: Aedes mosquitoes (which usually bite during the day with peaks during early and late afternoon/evening hours)
- Reservoir: Unknown
Signs and Symptoms
The incubation period (the time from exposure to symptoms) of Zika virus disease is not clear, but is likely to be a few days. The symptoms are similar to other arbovirus infections such as dengue, and include fever, skin rashes, conjunctivitis, muscle and joint pain, malaise, and headache. These symptoms are usually mild and last for 2-7 days.
Potential complications of Zika virus disease
During large outbreaks in French Polynesia and Brazil in 2013 and 2015 respectively, national health authorities reported potential neurological and auto-immune complications of Zika virus disease. Recently in Brazil, local health authorities have observed an increase in Guillain-Barré syndrome which coincided with Zika virus infections in the general public, as well as an increase in babies born with microcephaly in northeast Brazil. Substantial new research has strengthened the association between Zika infection and the occurrence of fetal malformations and neurological disorders. However, more investigation is needed to better understand the relationship. Other potential causes are also being investigated.
Zika virus is transmitted to people through the bite of an infected mosquito from the Aedes genus, mainly Aedes aegypti in tropical regions. This is the same mosquito that transmits dengue, chikungunya and yellow fever. However, sexual transmission of Zika virus has is also possible. Other modes of transmission such as blood transfusion and perinatal transmission are currently being investigated.
Zika virus disease outbreaks were reported for the first time from the Pacific in 2007 and 2013 (Yap and French Polynesia, respectively), and in 2015 from the Americas (Brazil and Colombia) and Africa (Cabo Verde). In total, 64 countries and territories have reported transmission of Zika virus since 1 January 2007.
Infection with Zika virus may be suspected based on symptoms and recent history of travel (e.g. residence or travel to an area where Zika virus is known to be present). Zika virus diagnosis can only be confirmed by laboratory testing for the presence of Zika virus RNA in the blood or other body fluids, such as urine or saliva.
- Vector control
Mosquitoes and their breeding sites pose a significant risk factor for Zika virus infection. Prevention and control relies on reducing mosquitoes through source reduction (removal and modification of breeding sites) and reducing contact between mosquitoes and people.
This can be done by using insect repellent regularly; wearing clothes (preferably light-coloured) that cover as much of the body as possible; installing physical barriers such as window screens in buildings, closed doors and windows; and if needed, additional personal protection, such as sleeping under mosquito nets during the day. It is extremely important to empty, clean or cover containers regularly that can store water, such as buckets, drums, pots etc. Other mosquito breeding sites should be cleaned or removed including flower pots, used tyres and roof gutters. Communities must support the efforts of the local government to reduce the density of mosquitoes in their locality. Efforts must be made to eliminate mosquito breeding sites such as still water soon after rains and its accumulation in discarded containers and waste materials in and around houses.
Repellents should contain DEET (N, N-diethyl-3-methylbenzamide), IR3535 (3-[N-acetyl-N-butyl]-aminopropionic acid ethyl ester) or icaridin (1-piperidinecarboxylic acid, 2-(2-hydroxyethyl)-1-methylpropylester). Product label instructions should be strictly followed. Special attention and help should be given to those who may not be able to protect themselves adequately, such as young children, the sick or elderly.
During outbreaks, health authorities may advise that spraying of insecticides be carried out. Insecticides recommended by the WHO Pesticide Evaluation Scheme may also be used as larvicides to treat relatively large water containers.
Travellers should take the basic precautions described above to protect themselves from mosquito bites.
- Sexual transmission
Sexual transmission of Zika virus is possible. All people who have been infected with Zika virus and their sexual partners should practice safer sex, by using condoms correctly and consistently.
Pregnant women’s sex partners living in or returning from areas where local transmission of Zika virus occurs should practice safer sex, wearing condoms, or abstaining throughout the pregnancy.
People living in areas where local transmission of Zika virus occurs should practice safer sex or abstain from sexual activity.
In addition, people returning from areas where local transmission of Zika virus occurs should adopt safer sexual practices or consider abstinence for at least 4 weeks after their return to reduce the risk of onward transmission.