Diseases: Which animal will trigger the next pandemic?

Rats are seen as disease spreaders, but new research shows that rodents and other city animals are actually less likely to cause the next pandemic than previously thought.

City rats are widely studied by scientists.

City rats are widely studied by scientists.

Researchers at Georgetown University in Washington studied data on nearly 3,000 mammals, expecting to find that those living in urban environments harbor more viruses that can be transmitted to humans.

They actually found that urban animals admittedly harbor 10 times more types of disease, but that a methodological bias may be involved: they have been the subject of 100 times more studies than their rural counterparts. Once this massive bias was corrected, the researchers were surprised to find that rats were no more likely to be the source of a new disease than other animals.

“Not a good idea to get too close to urban wildlife”

Greg Albery, scientist

Still, “it’s still not a good idea to get too close to urban wildlife,” said Greg Albery, who led the study published Monday in the journal Nature Ecology and Evolution.

“These urban animals are unlikely to be the source of the next ‘disease X’, but they are often still a source of important well-known diseases,” he told AFP, citing the example of leptospirosis, a bacterial disease commonly transmitted by rats.

Because we have studied animals living in cities for so long, “we know so much about their parasites that there are relatively few unknowns; rural wildlife is much more uncertain and more likely to provide us with the next big threat,” he said.

More in the woods

But humans being in regular contact with rats, it’s always fair to describe them as “disease sponges”, Jonathan Richardson, professor of urban ecology at the University of Richmond, told AFP.

Mr Albery and his study co-author Colin Carlson published research last week showing that climate change could increase the risk of further outbreaks.

They found that when animals like bats flee to cooler areas, they first mix with other species and create new opportunities for diseases that could later infect humans. However, according to Mr. Albery, urban mammals such as rats could play a role in this process.

His research on global warming also showed that new opportunities for viruses to jump between animals would now occur closer to populated areas, rather in forests.


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