Zika: all you need to know
September 9, 2016
Global health officials are racing to better understand the Zika virus after a major outbreak which began in Brazil last year and spread to many countries in the Americas and elsewhere. Reuters provides insight into the virus and the outbreak
What is the history of Zika?
The Zika virus is found in tropical locales with large mosquito populations. Outbreaks have been recorded in Africa, the Americas, Southern Asia and the Western Pacific. The virus was first identified in Uganda in 1947 in rhesus monkeys and was first identified in people in 1952 in Uganda and Tanzania. Two billion people in Africa and Asia are reportedly at risk of contracting the virus. Countries which have a “perfect storm” combination of high population, high mosquito activity and underfunded health services are vulnerable.
How dangerous is it?
The US Centers for Disease Control and Prevention concluded infection with the Zika virus in pregnant women was a cause of the birth defect microcephaly and other severe brain abnormalities in babies. The centre said now that the causal relationship had been established, several important questions must still be answered with studies that could take years.
According to the World Health Organisation, there is strong scientific consensus that Zika can cause the birth defect microcephaly in babies, a condition defined by unusually small heads that can result in developmental problems. In addition, the agency said it could cause Guillain-Barre syndrome, a rare neurological disorder that can result in paralysis. Conclusive proof of the damage caused by Zika could take months or years.
Brazil reports the number of confirmed cases of microcephaly at 1 835 as doctors and Brazilian health officials found some suspected cases of microcephaly were not the disorder. Suspected ones under investigation had declined to 3 257.
Brazil registered 91 387 probable cases of the Zika virus from February until April 2.
Research in Brazil indicates the greatest microcephaly risk is associated with infection during the first trimester of pregnancy, but health officials have warned an impact could be seen in later weeks. Studies have shown evidence of Zika in amniotic fluid, placenta and foetal brain tissue.
How far has it spread?
Active Zika outbreaks have been reported in at least 58 countries or territories, most of them in the Americas.
Africa: Cape Verde
Americas: Anguilla, Antigua and Barbuda, Argentina, Aruba, The Bahamas, Barbados, Belize, Bolivia, Bonaire, Brazil, British Virgin Islands, Cayman Islands, Colombia, Costa Rica, Cuba, Curaçao, Dominica, Dominican Republic, Ecuador, El Salvador, French Guiana, Grenada, Guadeloupe, Guatemala, Guyana, Haiti, Honduras, Jamaica, Martinique, Mexico, Nicaragua, Panama, Paraguay, Peru, Saba, Puerto Rico, Saint Barthelemy, Saint Lucia, Saint Martin, Saint Vincent and the Grenadines, Saint Eustatius, St Maarten, Suriname, Trinidad and Tobago, Turks and Caicos, US, US Virgin Islands and Venezuela.
Oceania/Pacific Islands: American Samoa, Fiji, Kosrae, Federated States of Micronesia, Marshall Islands, New Caledonia, Papua New Guinea, Samoa and Tonga.
What are the symptoms?
People infected with Zika might have a mild fever, skin rash, conjunctivitis, muscle and joint pain and fatigue that can last for two to seven days. But as many as 80 percent of people infected never develop symptoms. The symptoms are similar to those of dengue or chikungunya, which are transmitted by the same type of mosquito.
How can it be contained?
Efforts to control the spread of the virus focus on eliminating mosquito breeding sites and taking precautions against mosquito bites, such as using insect repellent and mosquito nets. US and international health officials have advised pregnant women to avoid travel to Latin American and Caribbean countries where they may be exposed to Zika.
Zika has been associated with other neurological disorders, including brain and spinal cord infections. The long-term health consequences are unclear. Other uncertainties surround the incubation period and how Zika interacts with other viruses.
Can Zika be transmitted through sexual contact?
The World Health Organisation (WHO) said sexual transmission was “relatively common” and had advised pregnant women not to travel to areas with ongoing outbreaks of Zika virus. It also advised women living in areas where the virus was being transmitted to delay falling pregnant.
The US Centers for Disease Control and Prevention was investigating several cases of possible sexual transmission. These involved transmission from men to their sex partners.
The centre issued recommendations for preventing and testing for Zika infection on July 25, warning that the virus could be transmitted through unprotected sex with an infected female partner.
A reported case of female-to-male sexual transmission in New York, and limited human and non-human primate data indicating Zika virus RNA can be detected in vaginal secretions, led to the new warning, the agency said.
The centre’s expanded warnings on sexual exposure to Zika cautioned against sex without a condom or other barrier method of protection with any person, male or female, who has travelled to or lives in an area with Zika, including female-to-female transmission with a pregnant partner.
Research released last month found the virus might spread sexually from a man to a woman, even if the man had no symptoms of Zika infection.
British health officials reported Zika was found in a man’s semen two months after he had been infected, suggesting the virus might linger in semen long after infection symptoms fade.
The Pan American Health Organisation said Zika could be transmitted through blood but this was an infrequent transmission mechanism. There was no evidence Zika could be transmitted to babies through breast milk.
The WHO has identified Zika cases in Argentina, Chile, France, Italy and New Zealand as probably having been caused by sexual transmission.
How do you treat Zika?
There is no treatment or vaccine for Zika infection. Companies and scientists are racing to develop a safe and effective vaccine for it, but the World Health Organisation said early this year it would take at least 18 months to start large-scale clinical trials of potential preventative shots.
A vaccine is not expected to be ready for widespread use for at least two or three years.
US government researchers said they had started their first clinical trial of a Zika vaccine.