Wed, 2019/04/24 - 11:03am
Zoonotic disease, disease that can be transmitted between humans and animals, requires extra attention to understand how it spreads. Middle East respiratory syndrome coronavirus (MERS-CoV) is one of those diseases – it can transfer between humans and dromedary, one-hump camels. About one-third of the human cases charted since 2012 have been fatal.
University of Guelph PhD candidate Dr. Emma Gardner, in the Ontario Veterinary College's (OVC) Department of Population Medicine, is determining environmental factors that affect MERS-CoV transmission to help prevent the spread of this potentially fatal disease and better inform at-risk individuals.
Early results show that cool, dry days with good visibility promote the spread of the disease from camels to humans.
“These results are similar to what is typically seen in respiratory diseases except for the findings regarding good visibility, but that could be explained by human behaviour,” says Gardner. “You’re more likely to spend time and be close to your camels when there is good weather and visibility.”
Human MERS-CoV cases have been seen in 27 countries. So far, all zoonotic cases have occurred in the Middle East; cases elsewhere were caused by people who picked up the infection in the Middle East and travelled. This respiratory virus can cause a range of symptoms from minor fever and coughing to pneumonia to severe acute respiratory disease. Researchers are focusing their attention on how to reduce spread due to the high frequency of severe disease.
By comparison, MERS-CoV in camels is mild and typically lacks signs of infection. At its worst, it causes camels to have a runny nose for a few days, meaning the disease is easily missed by camel owners and health professionals. About 90 per cent of adult camels in the Middle East have had MERS-CoV at some point, allowing many opportunities for human contact with the virus.
Fortunately, the virus isn’t highly contagious.
Humans must closely interact with infected camels or consume contaminated camel milk and meat products to contract the disease. Furthermore, camels do not naturally spread the virus to their milk and meat, these must be physically contaminated by the camel.
In fact, most transmission so far has occurred between humans in medical facilities once one human contracts the disease and seeks medical assistance.
Gardner and her advisory committee modelled daily weather measurements with new cases of disease in Saudi Arabia to determine what increases the chances of contracting the disease from camels. This led to the discovery that cool, dry days with good visibility increase the likelihood of contracting the disease from camels directly.
Now that researchers have a better understanding of the disease and what meteorological factors increase zoonotic transmission, they are looking to increase our ability to understand how and why MERS-CoV is spreading.
“We want to create a mathematical model to explore how the infection is spreading among camels,” says Gardner. “For example, using this model, we could hypothetically vaccinate half the camel population and then see how it would affect virus spread.”
To do this, researchers will be using MERS-CoV data in camels shared by colleagues in Kenya to build more detailed knowledge of factors affecting the disease. This information can then be put into the mathematical model to begin mapping out real-world scenarios.
“This disease is of huge public health importance,” says Gardner. “By working to understand the human-camel interface using a One Health approach, the idea that all individuals and species contribute to health, we can help prevent future MERS-CoV outbreaks by informing the public and policy makers.”
Photo credit: Emma Gardner (above)
Illustration: istoclphoto.com/ elenabs (right)