While this fall our avian flu attention has been focused on the rapid spread of HPAI H5N8 in both Europe and Asia, there are other - potentially more dangerous - avian subtypes in the wild. Unlike H5N8 - which has never been known to infect humans - the Asian strain of HPAI H5N6 can be lethal in humans.
Just months after the emergence of H5N8 in early 2014 (which followed H7N9, and H10N8 in 2013), we saw a new reassortant HPAI H5N6 burst onto the scene in Southern China, infecting (and killing) a 49 y.o. poultry dealer in Sichaun Province.
Over the summer of 2014 we began seeing scattered reports of H5N6 in poultry outbreaks in China, Laos, and Vietnam. Human infections remained rare - with only 4 reported up until December of 2015.
But the pace picked up considerably in 2016, with more than 24 cases reported in China since it first emerged, many of them fatal.
Curiously, even though the HPAI H5N6 virus has been detected in Vietnam, Laos, and Cambodia, only China has reported human infections. The last human case was reported in August of 2019.
HPAI H5N6 activity has declined sharply in China since their massive H5+H7 poultry vaccination campaign kicked off in the summer of 2017.
There are other HPAI H5N6 viruses that are of far lesser concern, including a European variant which appeared in 2016, and has also migrated to Asia. It is a descendant of HPAI H5N8, and while deadly to poultry, it has never been known to infect humans.
Which means that, until a genetic analysis can be done, we can't know for sure which HPAI H5N6 virus we are dealing with.
All of which brings us to a Vietnamese news story that hearkens back to the bad-old-days of the early-to-mid 2000's, when Vietnam was the world's hot spot for HPAI H5N1, and farmers were illegally disposing of dead or infected birds rather than report outbreaks to authorities.
A follow-up report, published today (Dec 9th) confirms the dead birds were positive for H5N6.
Beyond concealing an outbreak from authorities who will likely insist on culling a farmer's entire flock, the illegal dumping of infected livestock (a not uncommon practice) can further spread the disease.
Other incidents noted in this blog include:
In 2019 we saw scores of reports of dead pigs (presumably infected with ASF) dumped into rivers and streams in China (see Taiwan: Another ASF-Positive Pig Washes Up On Shore), which likely contributed to the rapid spread of the virus.
- In February 2016 several badly decomposed chicken carcasses were found on local beaches of Hong Kong (presumably dumped upstream the Pearl River in Guangdong Province) that tested positive for the avian H5 virus (see Hong Kong: Another H5N6 Positive Chicken Carcass).
- In previous years (2009-2012) we'd seen numerous similar reports - albeit with the H5N1 virus - of badly decomposed poultry carcasses washing up on the beaches of Hong Kong.
- But perhaps most famously, in 2013 - in Shanghai Govt.: Thousands Of Dead Pigs Retrieved From River - we saw reports of as many as 3,000 pig carcasses dumped in the Huangpu river - a tributary of the Yangtze - that provides many of the 23 million residents of Shanghai with their drinking water.
It is too soon to know whether these illegally dumped birds were infected with the more dangerous strain of H5N6, or if this outbreak extends beyond one farm.
But it is concerning to see a return to the old practices of midnight dumping of dead poultry, rather than reporting outbreaks to authorities, as infected carcasses may be accessed by other birds or animals, potentially spreading the virus further.