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When H7N9 emerged in China in early 2013, it became quickly apparent that many human infections were acquired via exposure to poultry at live bird markets (LBMs), and poultry market closures quickly became one of the primary defense against the disease.
In October of 2013 we saw a 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).
InterpretationThe following summer (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.
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.
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.Despite the evidence that it would greatly reduce the transmission of the virus, closing LMBs (Live Bird Markets) has always been a very tough sell to the Chinese people. 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 - 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.LBM closures in China - when they were ordered - have generally been targeted to cities or regions where recent human cases had been reported, and were usually short-lived; often lasting only a matter of days or weeks.
Meanwhile, LBMs in neighboring regions remained open, selling live birds at highly attractive prices.While the intent was that birds in a restricted region not be transported for sale elsewhere, it appears - at least based on the following PLoS One study - that some bird owners simply shipped their unsold inventory to more lucrative markets, and thereby helped spread the virus across China.
We've actually seen this kind of behavior, and similar results, before when H5N1 was aggressively hitting Egypt, Indonesia, and Northern India a decade ago (see India: Farmers Attempt To Smuggle Chickens).Demonstrating the inherent risks of taking half measures when trying to control an infectious disease - and the formidable power of the law of unintended consequences - we have some excerpts from a much longer study that tracks the spread of H7N9 following LBM closures in China.
Follow the link below to read it in its entirety.
Research Article
Closure of live bird markets leads to the spread of H7N9 influenza in China
Yin Li,Youming Wang, Chaojian Shen, Jianlong Huang, Jingli Kang, Baoxu Huang, Fusheng Guo, John Edwards
Published: December 12, 2018
https://doi.org/10.1371/journal.pone.0208884
Abstract
Following the emergence of H7N9 influenza in March 2013, local animal and public health authorities in China have been closing live bird markets as a measure to try to control the H7N9 influenza epidemic. The role of live bird market (LBM) closure on the spread of N7N9 influenza following the closure of LBMs during March to May 2013 (the first wave) and October 2013 to March 2014 (the second wave) is described in this paper.
Different provinces implemented closure actions at different times, and intensive media reports on H7N9 in different provinces started at different times. Local broiler prices dropped dramatically in places with outbreaks and more live chickens were transported to other LBMs in neighboring areas without human cases from infected areas when live bird markets were being closed. There were six clusters of human infection from March to May 2013 and October 2013 to March 2014 and there may have been intensive poultry transportation among cluster areas.
These findings provide evidence that the closure of LBMs in early waves of H7N9 influenza had resulted in expansion of H7N9 infection to uninfected areas. This suggests that provincial authorities in inland provinces should be alert to the risks of sudden changes in movement patterns for live birds after LBM closure or increased publicity about LBM closure.(SNIP)
Conclusions
Closure of live bird markets, adverse publicity and reduced prices has resulted in sudden changes in movements of live poultry in waves of H7N9, and these appear to have resulted in new clustering of human cases in neighboring provinces and other uninfected places.
Our findings suggest that authorities in uninfected districts should be alert to the risks of sudden changes in movement patterns for live birds after LBM closure or publicity about LBM closure. They should take care to strengthen biosecurity systems and movement controls and to prevent the risks to poultry and humans in their places.
(Continue . . . )
