What a difference a year makes.
In January of 2014 a new, HPAI H5N8 virus (which had only rarely been sighted in China before) turned up in a big way in South Korea’s poultry and wild bird population, and proceeded to infect dozens of farms, resulting in the culling of millions of birds.
The virus briefly appeared in Southern Japan (see Japan: Detection Of H5 Avian Flu At Poultry Farm) in April of last year, but was pretty much considered an `Asian’ problem – and one that was far less well distributed across the landscape than was H5N1.
But early last November the world awoke to find HPAI H5N8 had made its way to western Europe, when a farm in Germany reported the virus (see Germany Reports H5N8 Outbreak in Turkeys), followed 10 days later by reports from the Netherlands (see Netherlands: `Severe’ HPAI Outbreak In Poultry), and again from Japan (see Japan: H5N8 In Migratory Bird Droppings).
H5N8 Branching Out To Europe & Japan
Suddenly H5N8 was on the move, in a manner which we hadn’t seen since the great H5N1 diaspora of 2006 – when that virus spread out of Asia and into Europe, Africa, and the Middle East.
Soon the UK, Italy, China and Russia would be added to the list of nations where H5N8 was showing up, as would Taiwan towards the end of the year.
But the biggest surprise came when HPAI H5 virus literally crossed oceans and turned up – first in Canada’s Pacific Northwest (see Fraser Valley B.C. Culling Poultry After Detecting H5 Avian Flu) in early December – and then began spreading across the western United States (see EID Journal: Novel Eurasian HPAI A H5 Viruses in Wild Birds – Washington, USA).
And somewhat ominously, as H5N8 has arrived in Taiwan, Canada, and the United States, it reassorted with local avian flu viruses and produced unique reassortant viruses (H5N2 and H5N1 in North America, H5N2, H5N3 in Taiwan).
How viruses shuffle their genes (reassort)
Of these, H5N2 appears to be spreading the fastest, and causing the most damage to the poultry industry. But the possibility of seeing additional reassortments emerge is real, and their behavior – and their pathogenicity in birds and humans – is quite frankly, impossible to predict.
Yesterday the EID Journal published a dispatch on the recent arrival of these HPAI H5 viruses, their evolution to date, and how their propensity for viral reassortment may lead to the creation of additional subtypes in the future. I’ve only posted some excerpts, follow the link to read it in its entirety.
Author affiliations: US Geological Survey National Wildlife Health Center, Madison, Wisconsin, USA (J.S. Hall, R.J. Dusek); US Department of Agriculture, Athens, Georgia, USA (E. Spackman)
The movement of highly pathogenic avian influenza (H5N8) virus across Eurasia and into North America and the virus’ propensity to reassort with co-circulating low pathogenicity viruses raise concerns among poultry producers, wildlife biologists, aviculturists, and public health personnel worldwide. Surveillance, modeling, and experimental research will provide the knowledge required for intelligent policy and management decisions.
The recent introduction of highly pathogenic avian influenza (HPAI) subtype H5N8 virus into Europe and North America poses major risks to poultry industries, zoologic collections, and wildlife populations; thus, this introduction warrants continued and heightened vigilance.
First discovered in early 2014 in poultry and wild birds in South Korea, HPAI H5N8 virus apparently arose in China from reassortment events between HPAI subtype H5N1 virus (clade 126.96.36.199) and several low pathogenicity viruses (LPAIVs) (1–3). The H5N8 virus was subsequently detected in waterfowl in Russia in September 2014, and since then, H5N8 virus and reassortants have been detected in poultry and wild birds in Europe (Netherlands, Germany, Italy, the United Kingdom, Hungary, and Sweden), Taiwan, Japan, Canada (British Columbia), and the western and central United States (Washington, Oregon, California, Idaho, Utah, Minnesota, Missouri, Arkansas, Kansas, Wyoming, and Montana).
Wild waterfowl are a primary natural host for LPAIVs, and infection rates in these populations peak at autumn migratory staging locations, where large numbers of immunologically naive juvenile birds congregate (4). The HPAI H5N8 virus has apparently adapted to wild waterfowl hosts: few or no clinical signs or adverse effects are apparent in these hosts when infected with the virus. Thus, it seems probable that the virus was disseminated out of Russia into Europe, East Asia, and North America by migrating waterfowl during autumn 2014 (5).
The HPAI H5N8 virus has encountered, interacted with, and reassorted with co-circulating LPAIVs in migratory and overwintering waterfowl populations, creating new HPAI viruses (HPAIVs). In Taiwan, new Eurasian lineage reassortant HPAIVs (i.e., H5N2 and H5N3 subtypes) and the parental H5N8 subtype virus have been detected in poultry and wild birds (6). In North America, HPAI H5N8 virus continues to circulate among waterfowl and commercial and backyard poultry flocks. In addition, new HPAIV reassortants (i.e., H5N2 and H5N1 subtypes) that are combinations of HPAI H5N8 virus and genetic elements from Eurasian and North American viruses are also circulating in these populations (7,8) (Figure).
As HPAIVs continue spreading and evolving, the questions posed here, along with many more questions, will need to be answered to understand the risks to agriculture, zoologic collections, wildlife, and, potentially, human populations. As other researchers have recently pointed out, robust, targeted surveillance programs among wild birds (11) and poultry, modeling of the movements of HPAIV-infected wild birds, and experimental research studies will provide the knowledge required for intelligent policy and management decisions regarding agriculture, wildlife, and public health.
While we can’t know what new reassortments may appear next fall or winter in North America, the idea that somehow we in North America are somehow insulated from the Asian and Eurasian avian flu strains by oceans and distance seems pretty well demolished.
For more on how these viruses may be able to cross oceans and continents, you may wish to revisit: