New Delhi, June 17: Bengal and Bangladesh are among areas in Asia predicted to be the most suitable for infections of a dangerous strain of bird flu that spreads through live poultry markets and has killed over 125 persons in China over the past year.
An international team of researchers has identified Bengal and Bangladesh, the river deltas of Vietnam, and parts of Indonesia and the Philippines as zones with conditions conducive for the spread of avian influenza H7N9 if the virus is introduced there.
The team’s vulnerability mapping exercise, published today in the research journal Nature Communications, has also found that the local density of live poultry markets is the most important predictor for the risk of H7N9 infections.
“We’re not saying we expect to see this infection emerge in these areas,” Marius Gilbert, an epidemiologist in Belgium who specialises in livestock and poultry diseases said in a media release issued by the International Livestock Research Institute. “But the concentration of live poultry markets in these areas makes them very suitable for the infection should the virus be introduced there.”
China has experienced two epidemic waves of the H7N9 strain since it was first detected in March 2013. The World Health Organisation has documented over 400 confirmed human cases of H7N9 with 125 deaths from China and one case in Malaysia.
The H7N9 virus does not cause illness in poultry and could spread silently across poultry bird populations long before humans become infected and fall sick. The H7N9 infection causes the typical symptoms of flu — fever, cough, shortness of breath and severe respiratory illness, which in some cases may progress to death.
Gilbert and his colleagues from institutions in Asia, Africa, and Europe used the locations of over 8,900 retail and wholesale live poultry markets in China and H7N9 infection patterns observed thus far to develop a statistical model to predict the risk of H7N9 infection across Asia.
“The greatest risk beyond already-infected areas (in China) is estimated to be in the Bengal regions of Bangladesh and India, the Mekong and Red river deltas in Vietnam and isolated parts of Indonesia and Philippines,” the scientists said in their study.
The study has suggested that the existence of live poultry markets close to an environment rich in water such as rice paddy fields appeared to be a contributing factor associated with the first emergence of the virus.
The scientists said the identification of new vulnerable zones for H7N9 market infections could help in early detection of new incursions of the virus, early response and active containment to minimise the impact to human health.
But they point out that the absence of illness in poultry may require active surveillance in which poultry birds are periodically tested to determine whether they are infected with H7N9 or not.
The patterns of infection in China’s provinces has indicated that dense live poultry markets surrounded by poultry farming in landscapes marked by wetland agriculture may be hotspots for the emergence of new influenza viruses in humans.