Airborne flu detection at bird markets hints at human exposure risk

Chicken defeathering
Chicken defeathering

Chicken defeathering at a live-bird market in China., fotokon / iStock

Viable avian flu virus is easily detectable in the air of live-poultry markets, which may explain why those who visit markets but don't have direct contact with the birds become infected, according to air sampling from sites in China and Hong Kong.

A research team based at Hong Kong University isolated three subtypes during their sampling activities: H5N6, H7N9, and H9N2. They reported their findings today in the latest edition of Eurosurveillance.

Their results come just weeks after a report from Chinese researchers who isolated H5N6 during bioaerosol surveillance at live-poultry markets in the Guangdong province city of Zhongshan.

Role of defeathering devices

For the new study, the team sampled three different types of poultry markets in Guangzhou, which also in Guangdong province: a wholesale market, a mixed-animal market, and a retail market. They also obtained samples from a wholesale market in Hong Kong.

Using two different types of biaerosol samplers, the researchers collected air samples near poultry at different intervals in 2014 and 2015. They also collected environmental swabs.

Viral RNA and infectious virus of H5N6, H7N9, and H9N2 strains were detected mainly in particles 1 micrometer or larger from the air collected in poultry markets in Guangzhou. H9N2 from different lineages was detected in both the air and environment during all the testing months.

In terms of volume of airborne virus detected, use of defeathering devices increased the quantity of virus, while market closures reduced the amount of particles carrying viral material.

The researchers said the airborne virus findings are consistent with earlier findings of viral RNA in poultry farm air and from experiments in the United States that found infectious influenza viruses at swine barns and live-pig markets.

They said their results underscore the possibility of airborne transmission among poultry or between poultry and humans and could explain how some patients became infected with H7N9 in China despite no direct contact with poultry or poultry stalls.

Ghana reports more H5N1 outbreaks

In other avian flu developments, Ghana's agriculture ministry yesterday reported four more highly pathogenic H5N1 outbreaks that occurred over the summer, two in backyard birds and two at commercial farms.

According to a report to the World Organization for Animal Health (OIE), all occurred in the far southern part of the country—three in Greater Accra region and one in Central region. Most of the chickens affected were layers, but the virus also struck adult broilers and 8-week-old pullets.

Of 2,378 susceptible birds at the four locations, the virus killed 1,442, and authorities culled the remaining poultry as a virus control step.

Ghana, like a handful of other African countries, reported a recurrence of H5N1 in 2015 and has confirmed multiple outbreaks over the past several months.

See also:

Sep 1 Eurosurveill report

Aug 14 CIDRAP News scan "H5N6 isolated from China poultry market air sample"

Aug 31 OIE report

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