Zika virus

A technician holds up a container of water containing the eggs of Aedes aegypti mosquitoes

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 viruses, which have caused recurrent outbreaks in a number of countries.

Number of countries affected

The following 8 countries of the Eastern Mediterranean Region have recorded the presence of the Aedes aegypti mosquito, but with no documented past or current cases of Zika virus: Djibouti, Egypt, Oman, Pakistan, Saudi Arabia, Somalia, Sudan and Yemen.

None of the countries in the Region have reported either local transmission or importation of the Zika virus. Nevertheless, countries need to remain vigilant to prevent the spread of the virus, should it reach the Region. Epidemiological, laboratory and vector surveillance need to be strengthened at the national and sub-national levels to detect any sign of local transmission or importation.

As of March 2017, a total of 84 countries and territories around the world have reported transmission of Zika virus infection, of which 61 areas have ongoing transmission with new introduction or reintroduction reported since 2015.

WHO declared microcephaly and other neurological disorders associated with Zika virus a public health emergency of international concern (PHEIC) on 1 February 2016 due to the cluster of neurological disorders and neonatal malformations reported in the Americas Region. Following this announcement, more cases were reported in countries with known presence of mosquito vectors, and research has demonstrated the link between Zika virus infection and microcephaly. Thirty-one countries or territories have reported microcephaly and other central nervous system malformations potentially associated with Zika virus infection or suggestive of congenital infection.

Although the Zika virus and associated consequences remain a significant public health challenge requiring intense action, it no longer represents a PHEIC as defined under the International Health Regulations (2005). On 18 November 2016, WHO declared the end of the PHEIC for microcephaly and other neurological disorders associated with Zika virus.

There has been a decline in the number of reported cases of Zika virus infection in some countries, however there is no overall decline of the outbreak, and the global risk assessment associated with the virus remains unchanged.

Microcephaly and Guillain-Barré syndrome

There is now international scientific consensus that Zika virus is a cause of microcephaly and Guillain-Barré syndrome (GBS). As of February 2017, 30 countries or territories have reported microcephaly and other central nervous system malformations potentially associated with Zika virus infection, and 21 countries or territories have reported a rise in the number of cases of GBS and/or laboratory confirmation of a Zika virus infection among GBS cases.

Symptoms

Only 20% of people with Zika virus infection show symptoms, which include mild fever, skin rash and red eyes. These symptoms normally last for 2–7 days. There is no vaccine to prevent Zika virus infection and there is no specific anti-viral treatment available.