Tuesday, 20 August 2013

H7N9 and H5N1 may have emerged from birds around Taihu Lake

Wang and colleagues from the Institute of Disease Control and Prevention of People’s Liberation Army, Beijing, China and from The University of Queensland, Australia writing in Emerging Infectious Diseases, note that most (71%) people in China infected with influenza A(H5N1) virus (spanning from 14/10/2004-17/05/2013) had direct contact with poultry or their excrement. That contact includes work-related handling of live and dead birds and their urine and faeces.
However, most of those infected by influenza A(H7N9) virus had indirect exposure to live birds, mainly through visiting live bird markets (LBMs).

Also of interest, most H7N9 cases were more closely clustered  compared to the more widely spread H5N1 cases.

The authors were looking for an overlap between the earliest known cases of infection of both viruses - perhaps to find a common source of the emergence of these zoonoses - and their studies suggested Taihu (Tai Lake) Lake which is near Anhui province and Shanghai municipality and borders Jiangsu and Zhejiang provinces. All place names that were foci of a lot of H7N9 activity earlier in the year.

The authors conclude that this region may be a key hotspot for spillover of avian influenza to humans. This would be a useful place to add to the emerging influenzavirus watch list and bird sampling/genotyping list. They also reaffirmed the role of LBM visits were another key risk factor for acquiring H7N9.