Four confirmed cases of Zika virus in Canada

Ms. Chan said that while a direct causal relationship between Zika virus infection and birth malformations has not yet been established, it is “strongly suspected”.

There is no known vaccine or medicine to treat the Zika virus.

Another private vaccine developer, Boston-based Replikins Ltd, said it was preparing to start animal studies on a Zika vaccine in the next 10 days.

JOSUE DECAVELE/REUTERS A sterile female Aedes aegypti mosquito is seen on the forearm of a health technician in a research area to prevent the spread of Zika virus and other mosquito-borne diseases in Guatemala City.

The Zika virus is “spreading explosively” in the Americas, the head of the World Health Organisation said on Thursday, as the global health body warned that it expected up to four million cases of the disease.

Meanwhile, the US Food and Drug Administration said it was working to rapidly implement appropriate donor deferral measures for travellers who have visited affected regions in order to protect the blood supply.

The virus’ symptoms tend to be slight, and include fever, rash, pain or conjunctivitis.

Secretary for Food and Health Dr. Ko Wing-man also said that because only up to one quarter of the infected persons might develop relatively mild illness, “the attention was therefore not too big”. Severe disease requiring hospitalisation is uncommon and the case fatality rate is low.

Having eliminated the insect in the 1950s, Brazil is battling its resurgence with redoubled efforts as 4,000 birth defects have been reported this season there as against a normal of about 200 a year.

“What we have to assume is anywhere where they have the Aedes (mosquitoes), they could have the Zika virus and they should have the tools to be able to look for it”, he said.

Although nearly all cases involve transmission from the mosquitoes, the virus has been found in semen and there at least 2 cases of sexual transmission of the virus.

Researchers are also looking into a potential tie between Zika infections and cases of Guillain-Barre syndrome, which can cause temporary paralysis.

Colombia says it’s had about 16,500 suspected cases of Zika, though only a small fraction have been confirmed by laboratory tests.

The World Health Organization (WHO) now forecasts 3 to 4 million people could be infected with Zika virus in the Americas in 2016 and has labelled the virus as “spreading explosively”. Brazil reported the first cases of Zika in South America in May 2015. The ailment results in an abnormally small head in newborns and is associated with various disorders including decreased brain development. Most babies born with that condition die shortly after birth.

Jennifer House, the state public health veterinarian in Colorado, said the mosquito carrying the virus “is not present in Colorado”, because it prefers “more of a tropical type of environment”.

Some are concerned fear over the Zika virus could lead to more illegal abortions that jeopardize women’s health.

Taylor says women who are pregnant or planning to become pregnant, consult a health-care practitioner before travelling to a region where the virus is circulating.

Even where health inspectors are unlikely to find breeding mosquitoes, Brazil is taking every precaution.