OIE Feb HPAI Report - Non-Poultry, Wild Birds Jan 15th- Feb 4th
#15,824
When I began this blog, fifteen years ago, the world's attention was increasingly focused on a recently emerged HPAI H5N1 virus - first seen in Hong Kong in the mid-1990s - that was spreading globally via wild wild and domesticated birds, and occasionally jumping to to humans.
Killing as many as half of all hospitalized cases, this avian flu virus was viewed as potentially the cause of the next influenza pandemic.
As it turned out, H5N1 was beaten to the punch by a novel H1N1 swine-origin virus, which sparked a relatively modest pandemic in the spring of 2009. Over time, H5N1's threat began to fade, but it was quickly joined by a host of new pandemic threats, including avian H7N9, H5N6, and MERS-CoV.
In 2014, a particularly virulent H5N8 virus appeared in South Korean poultry, and within a year had crossed both continents and oceans, and sparked a major epizootic in the United States in 2015, and in Europe in 2016-2017.
The saving grace of HPAI H5N8 was that while it was easily carried by wild and migratory birds, and caused significant mortality in both poultry and wild birds, it didn't appear capable of infecting humans.
But with each passing year, we've seen studies showing that HPAI H5N8 was evolving and accruing genetic changes that might make it better adapted for mammalian hosts (see Vet. Research: Synergistic AA Changes That Enhance Virulence Of H5N8 In Mice).
The big pandemic threat, however, was viewed as H7N9 - which for 5 years had sparked yearly epidemics in China.
In the summer of 2017 China introduced a new H5+H7 poultry vaccine, which proved to be a rousing success. Not only was H7N9 quickly suppressed, H5Nx outbreaks in China - and around the world - began to plummet.
While H5N8 did not go completely away, it was largely subdued.
In early 2020, about the time that COVID-19 began to emerge, we started seeing fresh reports of HPAI H5N8 in Europe and Asia. Last fall, H5N8 returned with a vengeance, sparking the largest epizootics since 2017 (see OIE Feb Report below).
Throughout the fall we saw reports indicating that this year's H5N8 virus was `genetically distinct' from previously circulating strains in Northern Europe (see Pre-Print: Novel Incursion of a HPAI H5N8 Virus in the Netherlands, October 2020), indicating that the virus continued to evolve.
We've also seen numerous reassortment spinoffs (H5N5, H5N1, H5Nx) reported across Europe, reminding us just how promiscuous Clade 2.3.4.4 H5 viruses can be.
All of which means that H5N8's reported species jump to humans comes as not a complete surprise. In fact, this possibility is the primary focus of a journal article by Chinese and Scottish researchers published exactly 1 month ago today, in the journal The Innovation.
I've only included the opening paragraphs, so follow the link to read it in its entirety. When you return, I'll have a postscript.
Dealing with Highly Pathogenic Avian Influenza: An Impending Crisis
Received 30 December 2020, Accepted 16 January 2021, Available online 21 January 2021.
https://doi.org/10.1016/j.xinn.2021.100084 Under a Creative Commons license
Humans and other animals have always been battling viruses, especially those that cause emerging and re-emerging infectious diseases. Along with the ongoing COVID-19 pandemic, highly pathogenic avian influenza (HPAI) viruses of the H5 subtype are attacking silently as a re-emerging disease, thus seriously impairing poultry and human health. Recently, there have been outbreaks of the H5N8 subtype of HPAI virus in many regions around the world. According to data available through the Global Animal Disease Information System (http://empres-i.fao.org/) of the Food and Agriculture Organization of the United Nations, a total of 412 HPAI H5N8 outbreaks were reported worldwide from August 31 to December 1, 2020, with 353,851 animals confirmed to be infected in 26 countries around the world. Only sporadic cases of this strain were found during the same period in the previous year.
The HPAI H5N8 virus was first isolated in 2010. It belongs to the clade 2.3.4.4 of HPAI H5N1 (Gs/GD lineage), which undergoes reassortment, swapping its neuraminidase and other segments. HPAI H5N8 emerged and then spread intercontinentally. Multiple HPAI H5N8 outbreaks have occurred worldwide, with large epidemics in 2014/20151 and 2016/2017.2 At the beginning of 2020, H5N8 was again detected in Europe, and two novel strains of HPAI H5N8 were isolated in Germany. In October, a strain with high nucleotide homology to the German samples was isolated from field samples in South Korea, indicating that this strain had been transmitted intercontinentally. At present, it appears that these HPAI H5N8 strains have undergone further reassortments, although identification and analysis of the 2020 strains are still ongoing.
Although no HPAI H5N8 human infections have been reported so far, it still needs to be taken seriously (Figure 1). Strains of the clade 2.3.4.4 have been found to infect cats and pigs, and clade 2.3.4.4 H5N6 has caused infections in humans. Under laboratory conditions, some strains of the H5N8 subtype can seriously infect minks and transmit via direct contact. Whole-genome analyses of HPAI H5N8 have shown the molecular characteristics, including PB2-613I and PB2-702R, related to genes found in strains infecting human beings after the 2014 outbreak of HPAI H5N8, indicating that HPAI H5N8 has the potential to infect human beings to a certain extent.
While it is entirely possible that this event in Russia is a limited - perhaps even one time event - or that it might take years before H5N8 adapts well enough to humans to become a genuine threat, there are no hard and fast rules when it comes to viruses jumping species.
SARS-CoV-2 went from completely unknown, to a global crisis, in a matter of weeks.
We are almost a full year into a global influenza drought, and no one really knows how that might affect the ability for novel flu viruses to emerge once we lower our social distancing and personal protection defenses.
With community immunity to influenza viruses waning, and little competition from seasonal H1N1 and H3N2, conditions may be ripe for something new to come out of left field (see PLoS Comp. Bio.: Spring & Early Summer Most Likely Time For A Pandemic).
Admittedly, it would be horribly unfair to have to deal with another pandemic threat either during, or immediately after, COVID-19. The world badly needs a respite, and time to recover.
But the truth is, nature doesn't care about fair.
