Bird Flu Database Will Help Track Future Outbreaks

By Shweta Iyer on March 9, 2014 2:06 PM EDT

Mallard
With bird flu cases on the rise each year, a team of scientists have compiled a database with information on every strain of the flu virus found in birds around the world, which will help track outbreaks. (Photo: Brendan Lally, CC BY 2.0)

Avian influenza, also known as the bird flu, is caused by flu strains that sicken birds. Some of these viruses are highly contagious and sometimes spread to humans, and in recent years, they've spread at increasing rates. To better understand these pathogens, a team of international scientists, for the first time, have created a comprehensive global inventory of the viral strains in birds. The scientists collated the data by reviewing more than 50 published studies and genetic data.

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The research was conducted as part of the USAID PREDICT project, and was published in the open-source journal PLoS One. The scientists identified over 116 avian flu strains, a number that's two times the known number of strains in domestic birds and 10 times more than those found in humans. The prevalence of variety of these strains changed from one area to another.

Avian flu is almost unpredictable. Strains which were earlier known to be pathogenic only to birds have suddenly started infecting humans as well. In 2013, the H7N9 virus infected humans in China, leading to an outbreak with 144 cases by the end of the year. To date, there have been more than 300 clinical cases of H7N9, with a 33 percent mortality rate. Health officials were caught unaware because the strain had never sickened humans before. Earlier this year, in China, an avian flu strain H10N8 was detected in humans for the first time.

The transmission of the avian flu from birds to humans mainly comes from handling dead, infected birds. Three-quarters of the people who contracted the H7N9 virus had come in contact with domestic poultry. Although the viral strains often originate in wild birds, its spread among poultry and other livestock makes humans more susceptible to contracting it.

The scientists created the global avian flu inventory to better understand and monitor the different viruses. It will also enable health officials around the world to better tackle a future outbreak. "This snapshot of the world of flu virus diversity in birds is the outcome of many years of ecology and evolution, as viewed through the lens of surveillance methods utilized by scientists from around the world," said study lead author Dr. Sarah Olson, associate director of wildlife epidemiology at the Wildlife Conservation Society, in a statement.  

In order to correctly analyze and treat a particular disease it is important to accurately identify the source. But tracking the natural diversity in viruses can be a difficult task since they are so widespread. So the researchers introduced a new method, similar to the one used by ecologists, where they estimated the diversity of flu viruses in a particular location. With this approach, health authorities can design surveillance programs to detect a given percentage of flu virus diversity.

The scientists also identified flu diversity in the bird hosts that carry them. Mallards carry the highest number of strains (89), while ruddy turnstones hold the second most, at 45. The scientists concluded that strains that were widespread among many types of wild birds were more likely to spread among domestic birds too, therefore increasing the risk of a spillover scenario, in which the virus transfers to other species like humans. They also noted that some strains could be specific to certain bird types. For example, gulls and shorebirds carried ten strains that have not been identified in any other bird.

"This inventory isn't about blaming wild birds, but it allows us to map what we know, and informs our understanding of what drives viral diversity and the emergence of rare viral strains that can infect people," Olson said in the release. "Given that flu viruses can jump from domestic poultry to people, ongoing efforts at improving biosecurity at poultry farms and markets remain key to outbreak prevention."

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