Until recently, H7N9 has shown low pathogenicity, meaning that it may cause mild or no illness in poultry. Evidence from China’s Guangdong province suggests that the new strain has shifted to high pathogenicity in poultry while retaining its capacity to cause severe problems in humans. This is said to be a genetic change that could lead to high mortality for birds within 48 hours of infection and cause high economic losses for those engaged in poultry production and sales.
“China has embarked on intensified surveillance and results are awaited to better assess the epidemiology and potential spread of this new, highly pathogenic virus.”
Sophie Von Dobschuetz, FAO
Meanwhile, human cases of the H7N9 virus, first detected in China four years ago, have been increasing since December 2016. An update in March reported 20 human cases in eight Chinese provinces: Hunan, Jiangsu, Guangxi, Fujian, Guizhou, Chongqing, Shandong and Zhejiang, according to the Food and Agriculture Organisation (FAO). In the latest update (12 April), the FAO reported an additional 16 human cases and two detected in birds.
As before, most patients mentioned visiting live bird markets or coming into contact with infected birds. There is, however, no indication that the news strain has spread to wild birds.
“China has embarked on intensified surveillance and results are awaited to better assess the epidemiology and potential spread of this new, highly pathogenic virus,” Sophie Von Dobschuetz, animal health officer at FAO, tells SciDev.Net. “FAO, through its office in Beijing, is in regular dialogue with the ministry of agriculture and providing recommendations for surveillance and control.”
The H7N9 strain currently circulating in China has not been noted in poultry populations in other countries, Matthew Stone, deputy director general of the World Organisation for Animal Health, tells SciDev.Net.
“However, these countries (with poultry farms) remain at risk and need to be vigilant for a potential incursion of the virus, in a low or highly pathogenic form,” Stone adds. “Constant surveillance of domestic poultry as well as wild birds by national veterinary services is essential to reduce the risks associated with virus spread and protect both animal and human health, as well as livelihoods.” According to Stone, live bird markets remain the main source of virus spread among poultry and from poultry to humans and South-East Asian countries need to implement targeted and widespread monitoring to detect and respond to the virus.
Prevention measures should include laboratory testing, increased hygiene at live-bird markets and on-farm biosecurity to reduce exposure, he says.
This piece was produced by SciDev.Net’s Asia & Pacific desk.