Red alert to potential yellow fever epidemic

The deadly yellow fever virus has the potential to spread into cities around the world where it previously has not been seen, according to a new study led by St. Michael’s Hospital.

Researchers led by Dr. Kamran Khan of St. Michael’s have mapped the worldwide pathways through which yellow fever virus could spread by analyzing global patterns of airline travellers, the environmental conditions needed to enable transmission of the virus within a city, and countries’ requirements for travellers to provide proof of yellow fever vaccination upon entry.

Published in the Bulletin of the World Health Organisation (WHO), the research does not model a particular outbreak, but rather examines the potential spread for yellow fever virus to spread between the world’s cities.

“Imagine a yellow fever outbreak as a fire,” said Dr. Khan, who is a scientist at the Li Ka Shing Knowledge Institute of St. Michael’s Hospital. “Embers can fly off in different directions, and if they land in the right place, they can create another fire.

We studied the global conduits through which yellow fever virus can spread, and the potential for new yellow fever outbreaks to occur in the world’s urban areas.”

The team of researchers took a global panoramic view of yellow fever virus. They separated the world into three types of places: endemic areas, places where yellow fever virus is established; areas that appear suitable for yellow fever virus transmission but where it has not yet been seen; and non-endemic areas where there is no yellow fever virus and the environment appears unsuitable for it to spread.

Yellow fever is spread through the bite of an Aedes aegypti mosquito, which can also transmit viruses such as dengue, chikungunya and Zika.

According to the United States (U.S.) Centers for Disease Control and Prevention (CDC), about 15 per cent of people who get yellow fever develop serious illness that can be fatal.