H7N9 cases hit 122 since end of March

There have been 121 cases of human infection with H7N9 avian influenza in China and one case in Taiwan since March 31, according to a recent report.

The European Center for Disease Prevention and Control issued the update on Monday. H7N9 avian influenza was reported from eight provinces and two municipalities in China. One case and no fatalities were reported in Taiwan.

Health authorities in the affected areas are responding to the public health event with enhanced epidemiological and laboratory investigation, contact tracing and surveillance. Chinese health authorities found H7N9 avian influenza in ducks, chickens, pigeons and in environmental samples from live bird markets in Zhejiang, Anhui, Jiangsu and Shanghai provinces. Health authorities closed markets and culled poultry in the affected areas.

The mode and source of viral transmission are not yet confirmed. The virus causing the outbreak is a reassortant avian influenza virus with low pathogenicity for birds, which is why it is not causing the signal die-offs in poultry typically associated with pathogenic avian influenza strains. The H7N9 virus may have greater ability to infect mammals than most avian influenza viruses.

It is likely that the H7N9 avian influenza virus is spreading undetected in poultry populations and occasionally infecting humans with close contact to poultry or poultry products.

There is no evidence of sustained human transmissibility.

The ECDC anticipates increasing incidence of sporadic cases in China and possibly neighboring countries over the next few weeks.