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What if you had a crystal ball into the next major infectious disease like AIDS or Ebola?
Zoonotic or animal origin infectious diseases are born in animals and jump species to infect and kill humans. A team of scientists published a research paper Wednesday in the journal Nature say they have identified factors that may lead to predicting when and where an emerging infectious disease may arise or originate from.
Lead author of the study and an associate vice president for research at the global environmental health nonprofit EcoHealth Alliance Kevin Olival says "We actually know from previous studies and from what's happened in the past that most viruses come from mammals, not birds and not reptiles or other species."
To figure out what may end up creating an unexpected pandemic risk, Olival and his colleagues tried to address several elements to this puzzle. Olival said some animals are better sources or reservoirs for viruses than others "So the first piece is, really: What makes some species in the world better hosts for viruses or zoonotic viruses than other species?"
Olival, along with his colleagues created a database that included 586 unique viral species, which is every recognized virus that can be found in animals. And 754 mammal species, which is 145 of the mammal diversity found on the planet.
What they did next was analyze 2,805 mammal-virus association. For example, around 45% of the 586 viral species are detected in humans and out of those 45 % almost 72% have been detected at some point in a human and another species.
After applying mathematical models with their database, researchers were able to find that the risk of viruses jumping from mammals to humans differed depending on the how closely related a certain animal species was to us humans, along with how frequently they had contact with humans
However, there was an entirely independent variable.
Belonging to one set of animals instead of any other it made for a much more likely chance that certain creature may be a source of zoonotic viruses. Olival explained, For example, bats may not be closely related to humans, but they carry a "significantly greater proportion of zoonotic viruses than any other mammals,"
The researchers also used the database and mathematical tools to predict the number of viruses each specific animal might carry.
The second part of the puzzle was geography: Where might unknown zoonotic diseases be hiding?
The locations of each zoonotic virus animal host answered this. Zoonotic viruses arising from rodents were mostly found in North and South America and Central Africa, while zoonotic viruses carried by bats were grouped around South and Central America as well as parts of Asia according to the map Olival and colleagues marked up.
The final piece to this puzzle was figuring out what it is that make some viruses more likely than other to leap from animals to humans than others, Olival said. "I think that's a really important piece, and there's a lot more work that can be done, but we really provided a framework to move that predictive field forward."
Overall the new study "provides a roadmap for where in the world we should prioritize for finding and stopping the next emerging virus and that roadmap includes what species we should focus on and what locations are most important and what viruses should we be looking out for." Olival said.
The group's study took place over the course of six years.
The research is "very important." And "We are going to continue to have infectious disease threats, and it's basically one of the great scientific and medical challenges to keep pace with that," said Amesh Adalja, a spokesman for the Infectious Disease Society of America, and a senior associate at the Johns Hopkins Center for Health Security who was not involved in the study.
It should be noted that not everyone is at risk at least too much of a risk of catching a zoonotic infection. People like slaughterhouse workers and hunters are "basically at the leading edge of the human-animal interface," Adalja said, and so they are more likely to become infected by a zoonotic virus.
There is a large degree of interest in doing active surveillance on people of this nature, since what the new study is trying to establish "some type of analytical way of assessing the risk of these types of infections," Adalja explained, and "does, hopefully, make this a much easier prospect." Adding "As human beings expand their reach and live in many different areas where they traditionally haven't lived in, you will see more opportunities for novel viruses to appear. You can think about Lyme disease as a zoonotic infection," he said while pointing out that Lyme became a big health issue only when people started to live in places "that are more wooded."
Olival explains how human behaviors are a big factor in the materialization of these zoonotic infectious diseases. He said "Anything that puts us into contact with these mammal species that most people have never heard of, right, that might be living deep in the forest. So things like deforestation and road-building and hunting, all those factors are good examples of interactions that can actually cause diseases to come out of their natural habitat and jump into the human population."
Adalja said, not only does direct contact play a key role, temperature does also. Certain viruses, like for instance the flu, are more likely to be spread in cold conditions as opposed to hot. Saying "We know, for example, that diseases like yellow fever, which people now, in today's world, think of as a tropical disease, used to occur in Boston," for instance "mosquitoes have thrived in areas that aren't traditionally associated with mosquitoes."
Back in the days of George Washington's presidency a yellow fever outbreak in Philadelphia basically shut the whole government down because no one could meet in the former capital city Adalja said.
Speed of travel plays an integral part in the urgency of this new research. "It's very easy to be in a jungle in Africa or South America or the Indian subcontinent one day and in a Western city the next day," said Adalja.
Olival's shares the same concern saying with the current speed of travel infections can be carried from one side of the globe to the other in almost no time at all. While in the past this was not remotely possible. He concluded "My biggest fear is that a disease may emerge anywhere in the world, even in the most remote region of the world, and can arrive to a major US city in less than 24 hours"
Adalja stated the best way to handle this potential infectious threat is to really hone in on the viruses that are at the highest threat level and then try to intervene once you've identified it.