Temporary poultry market closures can drop environmental levels of H7N9 and other avian flu viruses, but after stalls reopen, contamination quickly returns to preclosure levels, Chinese researchers reported yesterday in Emerging Infectious Diseases.
The study took place in Guangzhou, the largest city in southern China's Guangdong province, during the second wave of human illnesses.
In response to rising numbers of human infections in the city in the first months of 2014, officials ordered a 2-week closure of live-poultry markets from Feb 15 to Feb 28. The markets were cleaned and disinfected at the start of the closure, and the team collected environmental samples from different areas of the markets before, during, and after the closure. Samples were tested by real-time reverse transcription polymerase chain reaction (rT-PCR) and culture.
During the closure period, H7N9 RNA detections fell by 79% and isolation decreased by 92%. The investigators also found that viable virus could still be cultured from wastewater about 2 days after poultry market closure. Chopping boards, often located at the front of the stalls, had the highest contamination rates of any other sampling site in the markets.
Investigators found, however, that virus returned to preclosure levels when the markets opened again, a rebound that requires further investigation, they wrote. The group added that, given little support for permanent poultry market closures, health officials could consider more ways to minimize risks to humans, including putting a screen between customers and the chopping board or redesigning stalls to limit transmission to humans.