Bird flu on the move in Europe and Asia, with poultry and human victims

Strains of the influenza virus similar to the ones that decimated Midwestern turkey and egg production in 2014 and 2015 are now wreaking havoc in poultry production in several parts of the world, including China where the virus has jumped species and infected and killed humans.

The World Health Organization said Monday that since mid-January, 304 people in China were confirmed to have infections caused by a strain of avian influenza known as H7N9, and 36 people had died. Media in Asia say the toll is higher: The South China Morning Post, based in Hong Kong, reported Wednesday that cases have been recorded in 16 provinces of China, and that there have been 87 deaths.

Image source: WHO

Meanwhile, tens of thousands of birds have died or been killed on affected farms, numbers that are recorded in reports to the World Organization for Animal Health. Sampling has shown that birds carrying H7N9 flu in one-third of the live markets in Guangzhou, outside Hong Kong, and regional governments in several provinces are pressuring markets to close down.

(A note on nomenclature: Flu strains are named for variations in two proteins on the surface of the virus, H for hemagglutinin and N for neuraminadase; there are 16 possible Hs and nine possible Ns, making for lots of combinations.)

Periodic outbreaks of avian flu strains, which are carried to poultry by wild waterfowl, have been a problem for at least 20 years. In 1997, a different strain, H5N1, infected birds in Hong Kong, jumped to humans, and killed six people. To shut down that outbreak, which health authorities feared might spark a global pandemic, the Hong Kong government ordered the slaughter of every chicken in the territory, more than 1 million of them.

Since then, there have been more than 800 cases worldwide of human infection with H5N1, and 452 deaths. The strain currently spreading in China, H7N9, is another of the small number of bird-flu strains that are known to jump species — and China is not the only place experiencing a spike in avian flu. On Wednesday, Taiwan reported a human case of H7N9 in a man who had visited mainland China.

Even when human infections have been limited, or outbreaks have died down quickly, bird flu has caused enormous losses in poultry production, from sick birds dying or unaffected birds being killed to stop the spread. In the United States in 2014-2015, more than 50 million birds died or were destroyed, and supplies and prices of poultry and eggs were affected for months. Last year, only one farm was affected, in Indiana, and 43,000 birds were killed.

In the current wave, 1.5 million birds have been killed in Asia and more than 4 million in Europe, according to the medical journal The Lancet.

Vietnam and Cambodia have both been contending with outbreaks of H5N1, a strain that in the past has jumped from birds to humans. South Korea has been trying to contain a different strain, H5N8, since the fall; the country has killed more than 30 million birds in an attempt to stop the spread.

That same strain also has been moving across Europe. It led to the prophylactic killing of more than a million ducks in France in January and so far this month. It is the second year in a row that France has been hit by bird flu. Ireland and the United Kingdom also are culling tens of thousands of birds; in the UK, all poultry producers have been required to bring birds indoors. There is no evidence that H5N8 can jump species to affect humans.

One reason for the vast losses in poultry is that “stamping out” — preventive killing — is the main strategy for limiting the spread of flu in birds; unlike in humans, vaccination is not part of the flu-prevention toolkit. That is partly because vaccines are expensive and partly because vaccinating birds prevents illness but not necessarily infection, allowing the virus to continue to spread.

But veterinary-health authorities are coming around to the possibility that vaccination may have to be a part of any effective bird-flu response, because the economic damage — and the human risk — can be so great. Following the Midwest outbreak, the U.S. Department of Agriculture solicited manufacturers to fill a vaccine stockpile. But flu, a virus that mutates rapidly, is a moving target. And as with human flu vaccines, manufacturing capacity and distribution infrastructure would be sorely stressed if a bird-flu epidemic began to move.

Maryn McKenna is the author of Superbug and Beating Back the Devil. She last wrote for FERN about how the Netherlands cut antibiotic use on farms. Her new book on antibiotics in agriculture will be published by National Geographic Books/Penguin Random House in 2017She writes regularly about antibiotics and agriculture for Ag Insider.