A firefighter in Brazil inspects a pool for mosquito larvae (photo courtesy Agência Brasília via flickr)

Zika virus: U of T experts on what you need to know

Most people infected will not even know they're sick, experts say, but link to birth defects “is a very active area of research now”

U.S President Barack Obama called for urgent action against the Zika virus on Jan. 27 as the World Health Organization predicted the mosquito-borne scourge will likely spread across the Americas.

The virus, which is linked to the birth defect microecephaly, where babies are born with unusually small heads, has been reported in more than 20 countries so far.

Earlier this week, health officials in El Salvador were warning women to avoid pregnancy until at least 2018 and Health Canada is advising women who are pregnant to avoid travel to infected areas.

“Zika is a flavivirus from the same family as dengue,” said Professor Jay Keystone of the Faculty of Medicine. “It is transmitted by a day-biting Aedes mosquito with peak biting times in the early morning and late afternoon.

“From a clinical perspective it produces a flu-like illness and rash similar to dengue fever but if the current theory holds up, it may be responsible for causing microcephaly in pregnant women who are infected during pregnancy. None of the other flavi-viruses do this.

“Also, rarely it may cause neurologic symptoms with ascending weakness from legs to the neck(Gulliane Barre syndrome.”

Keystone, an expert in tropical diseases, recommends travellers reduce the risk of bites by using “DEET-containing insect repellent at peak biting times” and wearing long-sleeved shirts and trousers. However, he cautions that mosquito-borne viruses travel with us and on our means of transportation such as airplanes and boats.

“It is likely that the virus will spread across the Atlantic to Asia and Southeast Asia eventually just as viruses from those areas, such as Chikungunya, have spread to the Western hemisphere.” 

Dr. Isaac Bogoch, an assistant professor at U of T and an expert in infectious diseases at Toronto General Hospital, spoke with CBC Radio's Matt Galloway about the virus. He said the disease, which was endemic in Africa for decades before spreading to islands in the South Pacific, appears to have spread to Brazil in 2014 and 2015.

“Over the course of the last six months it seems to have spread rather quickly throughout the Americas and all the way up to southern Mexico and all over the Caribbean now,” Bogoch told the CBC.

Bogoch said the exact association between the virus and the potential for birth defects is unclear. But he said the pregnancy warnings are being made out of “an abundance of caution” and that most people who are infected will have few symptoms.

“The vast majority of people who get infected with this virus will be completely fine. About 80 to 90 per cent of people will have no symptoms whatsoever and people who do have symptoms will have a typically mild course, maybe three days of mild fever, typically some muscle and joint pain maybe a rash.”

Pregnancy concerns have arisen in part because there has been a large jump in the number of cases of microcephaly in Brazil, Bogoch said, where “there are an estimated half a million to a million-and-a-half cases of Zika virus and there's been some soft clues showing that this virus has been present in the amniotic fluid of children who are born with microcephaly so “this is a very active area of research now.”

Listen to the complete interview on CBC

(Visit flickr to see the original of the photo used above)

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