Toronto - May 23, 2013 - Embargoed until 2:00 PM - An international team of scientists has proved that the H7N9 influenza virus is efficiently transmitted when animals are in close contact -- defined in the study as touching, coughing and the exchange of bodily fluids.
"This study was designed to give us clues about the transmission of H7N9 which has affected some humans in China," said David Kelvin, PhD, a senior scientist at the Toronto General Research Institute and Professor at the University of Toronto. "The animals used in the study had very mild clinical symptoms as a result of their exposure to the virus and it was clear that very close contact was required for transmission. It also appears that this virus in its present form does not transmit very well through the air."
The study, published in Science, conducted in China at Shantou University with the assistance of Kelvin and Dr. Michael Roehrl, a pathologist at the University Health Network, was started because, as of May 1, over 125 human cases have been confirmed in China with the majority of these people hospitalized and many suffering acute respiratory distress. Over 75% of these people had a history of contact with, or exposure to poultry before becoming ill.
Ferrets and pigs were used in the study and transmission in the ferrets occurred when the animals shared cages and had direct contact with each other but was much reduced if cages were well spaced, which demonstrated that airborne transmission is not a high risk for H7N9 in this animal model.
"This study, while conducted in animal models, tells us that close contact is required for transmission and that health care workers are at risk for transmission as they are in close contact with the individuals," said Kelvin. "It also demonstrated that airborne transmission was very difficult in the animal models, which is likely to be the case in humans as well."
The study was funded by the Li Ka-Shing Foundation and the National Institutes of Health (USA).
University Health Network (UHN) and Shantou University have a joint program in Shantou to examine emerging infectious diseases in China and South East Asia which enabled the scientists to study H7N9 very soon after the outbreak because of the unique team approach which put together the scientists of Shantou, UHN, Shenzhen Third People's Hospital, the University of Hong Kong, St. Jude's Research Hospital and the scientists from the National Health and Family Planning Commission in Beijing.
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