GENEVA • The mosquito-borne Zika virus, which is suspected of causing birth defects, is expected to spread to all countries in the Americas except Canada and Chile, the World Health Organisation (WHO) has said.
Zika has suspected but unproven links to microcephaly - in which babies born to women infected during pregnancy have abnormally small heads. The virus is already present in 21 of the 55 countries and territories across the Americas, the WHO said in a statement on Sunday.
But it stressed that the Aedes aegypti mosquito, which carries the Zika and also the dengue and chikungunya viruses, is already present in all countries in the Americas, other than Canada and Chile.
The WHO pointed out that since people in the region had not been exposed to Zika before it emerged in Brazil last May, they lacked immunity, allowing the virus to spread quickly. The United Nations health agency said it therefore "anticipates that Zika virus will continue to spread and will likely reach all countries and territories of the region where Aedes mosquitoes are found".
The virus may also spread through sexual contact. "Zika has been isolated in human semen, and one case of possible person-to-person sexual transmission has been described. However, more evidence is needed to confirm whether sexual contact is a means of Zika transmission," the WHO said.
There is currently no evidence of Zika being transmitted to babies through breast milk, the WHO said.
WHO chief Margaret Chan said at the organisation's executive committee meeting in Geneva yesterday that "the explosive spread of Zika virus to new geographical areas, with little population immunity, is cause for concern, especially given the possible link between infection during pregnancy and babies born with small heads".
A surge in incidents across Latin America has prompted some countries to warn pregnant women against travelling to the region - an alarming prospect for Brazil as it gears up to light the Olympic torch on Aug 5.
Rio de Janeiro has promised stepped-up measures to eradicate Zika virus-carrying mosquitoes at Olympic venues before the Games start. "The mayor's office will be intensifying inspections for the Olympics in August, despite this being a period with lower numbers of mosquitoes," the City Hall said in a statement on Sunday.
"About a month before the opening of the Games, a team will visit all competition sites to eliminate possible concentrations," the mayor's office said. It said its campaign would be helped by the fact that the Games will take place during the Southern Hemisphere winter, but there would still be an increase in preventive efforts.