Friday, February 17, 2017

Beijing Orders Closure Of Live Bird Markets To Control H7N9


The link between live poultry markets and the transmission of H7N9 to humans has been long established. In the summer of 2014, in CDC: Risk Factors Involved With H7N9 Infection we looked at a case-control study conducted by an international group of scientists, including researchers from both the Chinese and the US CDC which concluded.
Exposures to poultry in markets were associated with A(H7N9) virus infection, even without poultry contact. China should consider permanently closing live poultry markets or aggressively pursuing control measures to prevent spread of this emerging pathogen. 

In October of 2013 we saw another study (see The Lancet: Poultry Market Closure Effect On H7N9 Transmission) which found:
Closure of LPMs reduced the mean daily number of infections by 99% (95% credibility interval 93—100%) in Shanghai, by 99% (92—100%) in Hangzhou, by 97% (68—100%) in Huzhou, and by 97% (81—100%) in Nanjing. Because LPMs were the predominant source of exposure to avian influenza A H7N9 virus for confirmed cases in these cities, we estimated that the mean incubation period was 3·3 days (1·4—5·7).

LPM closures were effective in the control of human risk of avian influenza A H7N9 virus infection in the spring of 2013. In the short term, LPM closure should be rapidly implemented in areas where the virus is identified in live poultry or people. In the long term, evidence-based discussions and deliberations about the role of market rest days and central slaughtering of all live poultry should be renewed.

While the transmission of H7N9 (or H5N6, H5N1, H10N8, etc.) to humans is the most obvious threat from live bird markets, they also likely play a major role in the evolution (and creation) of novel flu viruses. 

As we discussed a little over two years ago in The Lancet: Interventions To Reduce Zoonotic & Pandemic Risks From Avian Flu In Asia, by bringing together - into very close quarters - many different types of  avian species (chickens, ducks, geese, quail, etc.) these markets provide an ideal environment for two or more avian viruses to infect the same host, which can drive reassortment, and the creation of new flu subtypes.

Despite the evidence that it would greatly reduce the transmission of the virus,  closing LMBs (Live Bird Markets) has been a tough sell to the Chinese public. Purchasing live market birds is deeply ingrained in their culture, as it reassures the buyer that the bird is both fresh and healthy.

In the spring of 2009 - after China was rocked by 7 human H5N1 infections, and 4 deaths that January - we saw China Announce A Plan To Shut Down Live Poultry Markets In Many Cities.  The idea was to permanently (or at least during the winter and spring months) shutter LBMs in `all large and medium-sized cities throughout China' within a year.  
A plan that, despite its good intentions, obviously never went anywhere.

Still, in years past - when H7N9 cases have been far fewer than during this 5th epidemic wave - hard hit provinces have shut down their live bird or poultry markets. Often for weeks, and almost always showing an immediate decline in human infections, despite ongoing black market sales of birds.

This year - for reasons that are difficult to fathom - market closures appear to have been far more sporadic, slower to be ordered, and have often only been for a few days duration. 

Overnight, however, there are reports that Beijing may be ordering a harder stance. 

A Xinhua report this morning, published by the Shanghai Daily, details the plans to close LBMs in regions where H7N9 cases have been reported.

China steps up prevention of human H7N9 avian flu

Source: Xinhua | February 17, 2017, Friday

The situation has prompted health authorities to step up prevention and control measures. The National Health and Family Planning Commission is training workers in screening and early diagnosis, and in treatment of critically ill patients. The commission has also ordered a ban on the live poultry trade in places where H7N9 cases have been reported.

On Thursday, Guangzhou, capital of south China's Guangdong Province, stopped live poultry trading for the rest of the month, with all poultry markets to be thoroughly disinfected.

Exposure to live poultry is the major source of infections, particularly in rural areas. All human infections in Guangdong originated in live poultry and February - March is a crucial time for epidemic control, according to the local health commission.

Zhejiang, with 35 human infections and 11 fatalities in January, is suffering the worst epidemic in three years. The virus was found in 40 percent of live poultry markets this month, compared with 10 percent in September. All rural live poultry markets there were closed from Saturday. The trade has been banned in the cities since 2014.

Live poultry sales have also been suspended in Xiamen, Suzhou and several cities in Hunan and Sichuan provinces.

The bans have greatly reduced the number of new infections in many regions, said Ni Daxin, deputy director of the emergency response center at the Center for Disease Control and Prevention. Ni suggested replacing live poultry with frozen birds to reduce the risk of infection.

(Continue . . . )

Popular or not - moving away from live bird markets is probably the only way for China to get a handle on their yearly H7N9 epidemic.  Whether they have the political will this time to see it through, remains to be seen.