Study finds long-distance migrant birds key to US H5N8 outbreak in 2015
The 2014-15 outbreak of H5N8 avian flu in Europe and then North America was likely driven by long-distant migrant birds and an unusually "promiscuous" clade, a study published today in Science found.
Scientists from 32 global institutions who form the Global Consortium for H5N8 and Related Influenza Viruses analyzed migration patterns of wild birds that were found to be infected with H5N8. They also constructed phylogenetic trees of viruses collected from 16 different countries from 2004 to 2015 to track virus evolution.
Their data suggest that H5N8 was most likely carried by long-distance flights of infected migrating birds from Asia to Europe and North America via their Arctic breeding grounds. The authors write that the virus likely spread along two main migration routes: (1) from the east Asia coast/Korean peninsula, north to the Arctic coast of the Eurasian continent, then west to Europe and (2) from the Korean peninsula, then east across the Bering Strait and south along the northwest coast of North America.
Their genetic analysis also found that "the hemagglutinin of clade 22.214.171.124 virus was remarkably promiscuous, creating reassortants with multiple neuraminidase subtypes." That led to rapid evolution of the highly pathogenic H5N8 strain.
Lead author Samantha Lycett, PhD, of the University of Edinburgh, said in a university news release, "Bird flu is a major threat to the health and wellbeing of farmed chickens worldwide. Our findings show that with good surveillance, rapid data sharing and collaboration, we can track how infections spread across continents."
In a commentary on the study in the same issue, Colin A. Russell, PhD, with the Department of Veterinary Medicine at the University of Cambridge, wrote, "Enhancing surveillance in wild birds where migratory flyways overlap, particularly the Arctic, could provide an early-warning system for the spread of new viruses. However, these overlaps cover huge geographic areas" and involve massive bird populations.
"We urgently require detailed assessments of where surveillance is most needed and could have the greatest impact."
The H5N8 strain first started causing outbreaks in Southeast Asia in 2014, then spread to Europe and North America, causing 48 million US poultry deaths and more than $3 billion in economic loss in 2015.
Oct 13 Science study
Oct 13 University of Edinburgh news release
Oct 13 Science commentary
US cost of nonvaccination calculated at more than $7 billion annually
Overall costs of health-related expenditures plus lost income and productivity of low vaccine uptake in adults for vaccine-preventable diseases in the United States amounts to over $7 billion per year, according to a study published yesterday in Health Affairs.
The researchers developed a cost-of-illness model for 14 vaccine-preventable diseases associated with 10 vaccines and multiplied the cost per patient by the number of cases in persons aged 19 years or older for 2015. The total economic burden across the population was nearly $9 billion (plausibility range $4.7 billion to $15.2 billion).
Based on vaccination uptake rates in 2015, the investigators calculated that $7.1 billion, almost 80%, of the total was accounted for by cases of the diseases in unvaccinated individuals.
The authors say their study "presents a more comprehensive analysis of the economic burden of vaccine-preventable disease among US adults than previously conducted" and "highlights the importance of increasing adult vaccine uptake" in the country. They express hope that their cost estimates "spur creative policy solutions" toward increasing vaccination rates and raise appreciation for the value of vaccination in people's minds as they make more informed choices.
The diseases included in the analysis were hepatitis A and B, shingles, human papillomavirus, influenza, measles, mumps, rubella, meningococcal disease, pneumococcal disease, tetanus, diphtheria, pertussis, and varicella.
Oct 12 Health Affairs abstract