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Ebola has spawned an unprecedented outbreak of American fear. But the truth is, this isn’t the first time a disease-causing pathogen has stormed our borders. The AIDS epidemic has posed an ongoing threat since the 1980s. There was a whooping cough outbreak in California in 2010. There have been too many foodborne illness outbreaks to count.
A new Brown University study suggests that the era of disease scares is far from over. In fact, the rate of infectious disease outbreaks is on the rise, according to the researchers’ analysis of 12,102 outbreaks of 215 diseases over 33 years (1980-2013). It’s not just the number of outbreaks that’s growing, either: The diversity of the diseases affecting humans is also increasing.
Why, in an age of modern medicine, are infectious diseases able to strengthen their foothold? “We are living in a much more interconnected world,” study author Samantha Rosenthal told Yahoo Health. “We’re interconnected person-to-person through travel and urbanization, but we’re also more interconnected with animals, like wildlife and livestock.” This creates more opportunity for zoonotic pathogens—Ebola included—to jump from their animal hosts to humans.
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Animal-borne Illnesses are the biggest threat. Zoonotic diseases—those that are passed between animals and humans—such as salmonella, influenza, and E. coli, accounted for 56 percent of the outbreaks in the study. (Salmonella caused the most outbreaks of any pathogen in the dataset, with 855 outbreaks reported since 1980.)
“We don’t always see them coming, because a lot of different factors have to align for a human to be exposed to an animal host,” Rosenthal said. “HIV started from an animal population. So did Ebola. The bird flu. Some of the bigger ones that we’ve seen in recent times—and that have caused the most concern—have been zoonotic.”
Human-specific pathogens, including gastroenteritis, pertussis (whopping cough), measles, and enterovirus, were the second most prevalent threat. “The human population is growing, and we’re going to be closer together in urban centers,” said Rosenthal. “So human-specific diseases will be more easily spread over time.”
But the study also revealed a promising trend: Despite the uptick in outbreaks, we’re seeing a decline in the number of people affected by each. “This means we’re probably getting better at managing emerging threats, even though they’re increasing,” explained Rosenthal. As infrastructure, health care, disease surveillance, sanitation, and awareness have improved globally, so has our ability to detect and manage outbreaks, “though clearly there is a lot more work to be done,” she said.
Although the Ebola crisis has, to some, suggested otherwise, Rosenthal considers the U.S. well equipped to handle any infectious-disease outbreaks that may come our way. But she cautions against viewing our country as an isolated bubble. “What we know from Ebola is that if outbreaks start in countries that don’t have the same infrastructure and resources [as the United States], we’re still at risk of getting them,” she said. “I do think we’re doing a good job here, but we need to increase our global communication and cooperative efforts.”
The infectious-disease database created for her team’s study may serve a critical role in those efforts. “We now have a giant dataset of outbreaks, which has not existed before,” Rosenthal told Yahoo Health. Researchers can now easily access this data to analyze what’s driving outbreaks, whether it’s increased global travel, urbanization, global warming, or human and animal migration. Identifying key drivers in the spread of disease “can help us better understand how to intervene,” she said.
The database may also allow researchers to flag hot spots where outbreaks are likely to strike, “so we can target our surveillance efforts more specifically to areas and disease types that are shown to be riskiest,” Rosenthal noted.
And that, hopefully, means the current Ebola crisis will be the last of its kind.
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