H5N1/flu (other types)

With the caveat that this is appears to be a limited outbreak, we have the first official word of HPAI H5N1 spillover from poultry to swine on an American farm.  

Regular readers know that for months there has been speculation over when HPAI H5 would spillover into North American pigs, since they been shown to be susceptible in other nations.

However, testing of livestock in this country for HPAI H5 is sporadic at best, and we don't have a good handle over whether there may be other spillovers on other farms around the nation.  Particularly since pigs may be able to carry the H5 virus asymptomatically.

While that may be good news for the pig, it doesn't prevent the virus from reassorting with other (swine or human) influenza viruses, or potentially transmitting to other hosts. 

Frankly, I won't even speculate on that one. 

It does appear that the `current' number is probably closer to 46, although it is generally assumed that this is a significant undercount. 

Stay tuned.

But, as we saw last week in SCI AM - A Bird Flu Vaccine Might Come Too Late to Save Us from H5N1 - there are many obstacles to overcome - including the growing public distrust of vaccines. 

Given the news last week that a pig in Oregon tested positive for the H5N1 virus, the following review article - recently published in the Journal Viruses on the ecology and distribution of influenza A viruses in swine - is especially timely.   

Swine (and Equines) are the only hosts known to be susceptible to all 4 types of influenza (A, B, C & D), and reassortment in swine has been linked to the generation of previous pandemic viruses. 

Thousands of migratory seabirds have been discovered washed up dead or starving along beaches from North Queensland to Tasmania.

About 2,000 carcasses were found at one New South Wales beach this week, according to seabird research group Adrift Lab.

From October to November, migrating short-tailed shearwaters travel to their breeding sites along the Australian east coast from places like Siberia, Japan and South America.

Wildlife rescue volunteers say the looming threat of the lethal bird flu strain H5N1 is adding another layer of burden to the already busy period.

Even if we get lucky, and H5 doesn't have what it takes to spark a pandemic, there's no lack of other contenders in the wild.  Whether from an influenza virus, a coronavirus, `Disease X', another pandemic is inevitable. 

Which is why, in 2021's PNAS Research: Intensity and Frequency of Extreme Novel Epidemics, researchers estimated our pandemic risk may increase 3-fold over the next few decades. 

Although the spillover of HPAI H5N1 into mammals has most of our attention, H5 influenza continues to evolve, and over the years has produced dozens of clades and subclades, hundreds of genotypes, spanning  9 different subtypes (H5N1-H5N9).  

Many have failed to thrive, or gone extinct, but new variations continue to appear. 

While China's H5N6 virus is arguably the most concerning of these offshoots, we've also been following the spread of HPAI H5N5 in Europe - and its crossing over into Canada - with considerable interest. 

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Last July, in Cell Reports: Multiple Transatlantic Incursions of HPAI clade 2.3.4.4b A(H5N5) Virus into North America and Spillover to Mammals, researchers reported finding the mammalian adaptive E627K mutation in a number of samples.

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While it isn't clear how much of a player H5N5 will become, it has been increasingly reported across Europe, has crossed the Atlantic several times, and Ferrets inoculated with A(H5N5) viruses showed rapid, severe disease onset, with some evidence of direct contact transmission.

Given HPAI H5's track record, this is an avian flu variant we need to keep an eye on.