Dengue fever attracts little attention in Canada, yet this potentially lethal mosquito-borne disease is emerging as a growing global public health threat that could impact North America.

Forty years ago, the disease struck only nine countries; it's now endemic in more than 100. It is estimated that each year approximately 500,000 dengue infections progress to life-threatening disease, causing 20,000 to 25,000 deaths. This week the first cases of dengue fever in four decades were reported in Florida.

Mark Loeb, professor of pathology and molecular medicine in the Michael G. DeGroote School of Medicine, has been awarded $10 million from the U.S. National Institutes of Health (NIH) to conduct a large scale international study on the genetic variations which predispose people to the dengue infection. The funds are from the Department of Health and Human Services, National Institute of Allergies and Infectious Diseases of the NIH.

“We will get a blood sample from people who have been infected with dengue and compare them to milder cases, looking for genetic variants – such as vitamin D receptors – which have been previously described as important factors,” said Loeb, a microbiologist and infectious disease expert.

“Dengue used to be endemic in North America. There is concern now that global warming may eventually contribute to a resurgence of dengue.”

About 9,000 samples will be sent to McMaster for analysis from Honduras, Nicaragua, Mexico, Columbia, Thailand, India and Vietnam.

The dengue flavivirus, which causes dengue fever, is transmitted by a mosquito bite. Infection can cause diseases ranging from dengue fever, a flu-like illness, to dengue hemorrhagic fever or dengue shock syndrome which can be life-threatening. No vaccines or drugs have yet been developed to combat the infection.

The World Health Organization (WHO) estimates that about 2.5 billion people, or 40 per cent of the world's population, live in areas where there is a risk of dengue transmission. The infection hits hardest in the tropical and sub-tropical areas of southeast Asia and Latin America. In Canada, there are between 40 to 50 cases of dengue confirmed by laboratory testing each year.

During his five-year study, Loeb will look at three distinct groups: Individuals infected with severe, hemorrhagic dengue fever, others with milder dengue fever and a third group who are infected but show no symptoms.

“We will do comparisons, and then undertake a statistical analysis assessing frequency of genetic variants. The goal is to understand the genetic variants which predispose individuals to dengue,” he said.

Loeb is working with investigators in all countries from which samples are being sent, including Scott Halstead and Eva Harris, leading world authorities on dengue who are affiliated with the Pediatric Dengue Vaccine Initiative. At McMaster, the research team includes Jonathan Bramson, Guillaume Pare, Karen Mossman and Chanchun Xie.

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