Thursday, March 2, 2023

Bird Flu

What do dead sea lions on the beaches of Peru, minks on farms in Spain, otters and foxes in the U.K. and dead grizzly bears in the U.S. have in common? Avian flu, otherwise known as bird flu. Along with thousands of pelicans, various migratory birds, and millions of domestic chickens, turkeys, and ducks, this recurring virus has killed, it has now managed to spread into a variety of mammals as well and is posing a potential threat to humans.

Of the three types of influenza that infect humans (A, B, C) it is type A that has the zoonotic properties, (i.e. animal to human and vice versa) we are worried about and there have now been 6 avian subtypes that have infected humans; H5N1, H7N3, H7N7, H7N9, H9N2, and N10N8.

Avian flu infects the respiratory and gastrointestinal tract of birds and has been identified in more than 100 different species of wild birds around the world. Wild aquatic birds such as gulls, cranes, and shorebirds, and wild waterfowl such as ducks, geese and swans are considered natural hosts for bird flu viruses. Most wild birds with viruses are asymptomatic but can infect domestic poultry through their droppings. 

H5N1 first appeared in 1997 in China and killed millions of birds throughout Asia, Europe and Africa directly with millions more culled to prevent further spread. In 2022 alone there were over 50 million chickens culled in the U.S. and 5 million in Canada. However, the threat to humans has been low with only 1,000 people to date who have been infected, but more than half of them died with a mortality rate of around 60% or roughly 10 x that of COVID. Another strain, H7N9 also first appearing in China in 2013 and since then another 1,000 people have become infected with about the same mortality rate. The good thing is that avian flu does not appear yet to spread from human to human but rather from working with infected birds in the slaughter and plucking process. For the other mammals who died it was likely because they ate an infected bird.

However, with a mink to mink transmission of H5N1, the first among mammals, what is worrying health officials is the development of a human to human version of avian flu. Particularly in Asia, where the conditions there have humans, swine and poultry often in close proximity to one another, and able to infect one another, which could lead to a mixture of a pathogens that could create a human avian influenza. Recent research into the genes of the 1918 Spanish flu, which infected a third of the world population and killed 50 million or more people, indicate it was also a strain of both human and avian genes.

After everything we went through with COVID I think it's obvious the world can't be trusted to handle another epidemic, but it seems it is only a matter of time before something like bird flu makes its appearance. When it does watch out and remember hope is not a survival strategy. In the meantime, if you see a dead bird don't pick it up with your bare hands, put it in a plastic bag and dispose of it in the trash.

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