Intense circulation of A/H5N1 and other avian influenza viruses in Cambodian live-bird markets with serological evidence of sub-clinical human infections

Extensive genetic analysis of circulating bird flu strains in live bird markets could detect novel strains and inform market management. When there are multiple flu strains in one place new strains are more likely to emerge, because two different ‘parent’ strains can merge within an infected host. Phillippe Buchy and Paul Horwood at the Institut Pasteur in Phnom Penh, Cambodia, and co-workers conducted genetic analyses of viral strains from poultry, humans, water and soil at four Cambodian bird markets in 2013. They found that 45% of all samples tested positive for influenza, mostly the H5N1 strain but also nine other less pathogenic strains. Virus levels were especially high in water used to wash carcasses. Careful management of the markets is needed at busy times, particularly during the Lunar New Year Festival between January and March.