Zika virus Introduction Zika virus is an emerging mosquito-borne virus that was first identified in 1947 in monkeys. It was subsequently identified in humans in 1952. Prior to 2015, outbreaks had been recorded in Africa, the Americas, Asia and the Pacific.
The current outbreak began in 2015 in South America and remains largely limited there, but we all need to be alert in case someone travels back with symptoms. The disease is self-limiting and clears by itself. Only 20% have symptoms. The main concern is that cases of microcephaly have been noted to be on the rise in South America among newborns and it is suspected to be associated with Zika during pregnancy.
Zika virus disease is caused by a virus transmitted by Aedes mosquitoes. People with Zika virus disease usually have a mild fever, skin rash (exanthema) and conjunctivitis. These symptoms normally last for 2-7 days. There is no specific treatment or vaccine currently available. The best form of prevention is protection against mosquito bites. The virus is known to circulate in Africa, the Americas, Asia and the Pacific.
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. 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 Zika virus infections in the general public as well as an increase in babies born with microcephaly in northeast Brazil. Agencies investigating the Zika outbreaks are finding an increasing body of evidence about the link between Zika virus and microcephaly. However, more investigation is needed before we understand the relationship between microcephaly in babies and the Zika virus. Other potential causes are also being investigated.
Transmission 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. Zika virus disease outbreaks were reported in 2015 from the Americas (Brazil and Colombia) and Africa (Cape Verde). More countries in the Americas have reported sporadic Zika virus infections indicating rapid geographic expansion of Zika virus. These include Barbados, Bolivia, Brazil, Colombia, Dominican Republic, Ecuador, El Salvador, French Guiana, Guadeloupe, Guatemala, Guyana, Haiti, Honduras, Martinique, Mexico, Panama, Paragua, Puerto Rico, Saint Martin, Suriname, U.S. Virgin Islands, Venezuela and Samoa. (Source:
http://www.cdc.gov/zika/geo/).
Diagnosis Zika virus is diagnosed through PCR (polymerase chain reaction) and virus isolation from blood samples.
Prevention Mosquitoes and their breeding sites pose a significant risk factor for Zika virus infection. Prevention and control relies on reducing mosquitoes and reducing contact between mosquitoes and people.
This can be done by using insect repellent; wearing clothes (preferably light-coloured) that cover as much of the body as possible; using physical barriers such as screens, closed doors and windows; and sleeping under mosquito nets. It is also important to empty, clean or cover containers that can hold water such as buckets, flower pots or tyres, so that places where mosquitoes can breed are removed.
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.
Treatment Zika virus disease is usually relatively mild and requires no specific treatment. People sick with Zika virus should get plenty of rest, drink enough fluids, and treat pain and fever with common medicines. If symptoms worsen, they should seek medical care and advice. There is currently no vaccine available.
Travel advisory 1. Staff and families traveling to or resident in affected areas should take the basic precautions described above to protect themselves from mosquito bites.
2. Expectant women are advised to postpone or defer travel to affected areas.
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