* How do people become infected?
The virus is transmitted to people through the bite of infected female Aedes mosquitoes, the same type of mosquito that spreads dengue, chikungunya and yellow fever. The Pan American Health Organization (PAHO) said Aedes mosquitoes were found in all countries in the Americas except Canada and continental Chile, and the virus would likely reach all countries and territories of the region where Aedes mosquitoes were found.
* How do you treat Zika infection?
There is no treatment or vaccine available for Zika infection. Companies and scientists are racing to develop a safe and effective vaccine for Zika, but one is not expected to be ready for months or years.
* How dangerous is it?
The PAHO said there was no evidence that Zika could cause death, but some cases had been reported with more serious complications in patients with pre-existing medical conditions.
The virus has been linked to microcephaly, a condition in newborns marked by abnormally small heads and brains that have not developed properly. It also has been associated with Guillain-Barre syndrome, a rare disorder in which the body’s immune system attacks part of the nervous system. Scientists are studying whether there is a causal link between Zika and these two disorders.
* How is Zika related to microcephaly?
Health officials have yet to establish a direct causal relationship between Zika virus infection and birth defects, but it is strongly suspected. Brazil has reported more than 4000 cases of suspected microcephaly that may be linked to Zika. Researchers have identified evidence of Zika infection in 17 of these cases, either in the baby or in the mother.
It is unclear whether in pregnant women the virus crosses the placenta and causes microcephaly. Research in Brazil indicates the greatest microcephaly risk appears to be associated with infection during the first trimester of pregnancy.
* What are the symptoms of Zika infection?
People who get Zika virus disease typically 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 per cent 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 Zika 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 health officials have advised pregnant women to avoid travel to Latin American and Caribbean countries where they may be exposed to Zika.
* How widespread is the outbreak in the Americas?
Health officials said Zika outbreaks had been reported in at least 26 countries in the Americas.
Brazil has been the nation most affected. Other nations and territories include Barbados, Bolivia, Colombia, Costa Rica, Curacao, Dominican Republic, Ecuador, El Salvador, French Guiana, Guadeloupe, Guatemala, Guyana, Haiti, Honduras, Jamaica, Martinique, Mexico, Nicaragua, Panama, Paraguay, Puerto Rico, Saint Martin, Suriname, Venezuela and the US Virgin Islands, according to the PAHO.
* What is the history of the Zika virus?
The Zika virus is found in tropical locales with large mosquito populations. Outbreaks of Zika virus disease 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, according to the World Health Organization.
* Can Zika be transmitted through sexual contact?
Two cases of possible person-to-person sexual transmission has been described, but the PAHO said more evidence was needed to confirm whether sexual contact was a means of Zika transmission.
