A group of international scientists have completed the first global inventory of influenza strains in birds by reviewing more than 50 published studies and genetic data, providing new insight into the drivers of viral diversity and the emergence of disease that can ultimately affect human health and livelihoods.
The research, published in the journal PLOS ONE and performed as part of the USAID PREDICT project, identified more than 116 avian flu strains in wild birds. This is roughly twice the number found in domesticated birds, and more than 10 times the number found in people. Additionally, an analysis of studies that sampled more than 5,000 birds suggested some regions may have more viral diversity than others.
Avian flu outbreaks come with no warning. In 2013, an H7N9 avian flu strain caused a deadly outbreak in people in China. This surprised virologists, as the strain had never before caused disease in humans. To date, there have been more than 300 clinical cases of H7N9 with a 33% mortality rate. This year, another strain known to infect birds, H10N8, has caused human cases for the first time.
As was the case in the H7N9 outbreak, most direct bird-to-human spillover events (when a virus jumps from one species to another) of avian flu can be traced back to human contact with domestic poultry, according to an announcement from the Wildlife Conservation Society (WCS).
In an effort to improve preparedness, scientists are looking to better understand and monitor the diversity of all avian flu viruses — not just those known to cause disease. Completing the first global inventory of flu strains in birds is a key step in building that understanding.
"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 Dr. Sarah Olson, WCS associate director of wildlife epidemiology.
Understanding the natural diversity of viruses is critically important to identifying health risks. However, authorities face a challenge, both in focusing efforts in the right places and adequately financing surveillance to describe global flu diversity. To address this, the authors introduced a new method that borrows on approaches used by ecologists to estimate 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.
According to Olson, "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. 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."
The study can be found at http://dx.plos.org/10.1371/journal.pone.0090826.