​​​Image of Dr. Isaac Bogoch
Toronto General Hospital Tropical Infectious Disease specialist Dr. Isaac Bogoch was part of the team that mapped out the spread of the Zika virus. (Photo: UHN)​

A mosquito-borne virus, with a possible link to birth defects, is spreading rapidly across South and Central America, and the Caribbean, with potential to reach the United States, according to infectious disease specialists at Toronto General and St. Michael's Hospitals.

In Correspondence published in The Lancet, Toronto General Hospital Tropical Infectious Disease specialist Dr. Isaac Bogoch, Dr. Kamran Khan, Infectious Disease physician at St. Michael's Hospital, and co-authors map out the spread of the Zika virus, typically found in Africa and Asia-Pacific, across South and Central America, resulting in an epidemic in Brazil. Estimates in Brazil range from 440,000 – 1,300,000 cases.

Soon after the article was published, the U.S. Centers for Disease Control and Prevention advised pregnant women against travelling to Latin America and the Caribbean.  This is the first time the department advised pregnant women not to travel to a specific region during an outbreak.

Birth defects

Concurrent with the epidemic in Brazil, there has been a surge in infants born with microcephaly, along with detection of the virus in the amniotic fluid of affected newborns.  Microcephaly is a birth defect in which a baby is born with a smaller than normal head, indicating an underdeveloped brain. The number increased from 200 in 2014 to 3,000 in 2015.

In their Correspondence, the authors map out high-risk international pathways of the Zika virus, along with geographical areas that encourage its spread, through mapping climate, temperature, mosquito populations, and airline flight patterns.

Their mapped data show that more than 60 per cent of the population in Argentina, Italy and the U.S. live in areas that are susceptible to seasonal or summer Zika virus transmission, while Mexico, Columbia and the U.S. have millions of people living in areas that are at risk for year-round transmission.

No vaccine

The virus has the potential to spread rapidly across Latin America and the Caribbean, especially as people there do not have immunity against this virus. To date, Canada's climate is not conducive to its spread. There have been no reported cases of locally acquired Zika virus in Canada, although a British Columbia resident who recently travelled to El Salvador has contracted Zika virus in that region.

No vaccine or therapy is currently available to treat it.

"The world we live in is very interconnected now," says ," Dr. Bogoch, who is an assistant professor at the University of Toronto. "Things don't happen in isolation anymore. Infections from the far corners of the world can quickly reach us here on our doorstep,"

Zika virus is transmitted by Aedes mosquito species, which bite during the day, unlike night-biting mosquitos which may transmit infections such as malaria.

Dr. Bogoch advises that all travellers protect themselves from mosquito bites when travelling to areas the Zika virus is circulating. Mosquito repellent, as well as long sleeves and long pants are recommended.  Symptoms include fever, headache, rash, along with joint and muscle pain. ​

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