Most of the infectious diseases that emerge as human epidemic originated from mammals.

The virus behind the Ebola outbreak that has killed thousands in West Africa is believed to have been carried by fruit bats. The Middle East Respiratory Syndrome (MERS) and HIV, which have also claimed lives, are also linked to camels and chimpanzees, respectively.

The transmission of deadly diseases from animals to humans poses concern but researchers know very little about the patterns of such pathogen transmission.

In an effort to improve prediction of future mammal-to-human disease transmissions, Barbara Han, from the Cary Institute of Ecosystem Studies in New York, and colleagues have come up with maps that show the current reservoirs of viruses, bacteria, parasites and fungi that cause zoonotic diseases, or those that can spread between animals and humans.

Han and colleagues tracked the classes of animals that harbor known human pathogens and where these reservoirs tend to be found and had this reflected in maps, which were featured in Trends in Parasitology on June 14.

The maps showed hotspots of zoonotic animal hosts which include MERS-carrying camels, rabid bats, and more than 2,000 species of rodents.

The researchers expected and later confirmed hotspots to be in high biodiversity regions such as Central and South America, Central East Africa and Southeast Asia. Europe was also identified as a hotspot for zoonotic diseases.

"In general, these regions align with global geographic patterns of mammal biodiversity with the exception of the hotspot in the north temperate zone (Europe), which contains a higher diversity of mammal hosts than expected from global biodiversity patterns," Han and colleagues wrote.

"We postulate that this pattern may be driven in part by the high richness of rodents and insectivores found in this region."

While outbreak of diseases associated with pathogens that come from non-human hosts is not inherently predictable, the maps show understudied patterns. Knowing the hotspots and being able to study the diseases that animals carry may also possibly help researchers prepare for potential transmission of diseases from animals to humans.

Researchers noted the importance of shifting strategy from "putting out fires" to being preemptive: that is, to know where and what's carrying diseases and what's their distribution.

"Understanding where animals are distributed and why may not seem applicable to our day-to-day lives," Han said.

"But the big breakthroughs that we need as a society (e.g., forecasting where the next zoonotic disease may emerge) rely on exactly this kind of basic scientific knowledge."

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