Although the Chinese press can often be faulted for selective reporting, since the emergence of the H7N9 virus two years ago we’ve seen some refreshingly straightforward talk coming out of China’s scientific community.
Unlike with the SARS epidemic of 2003, we’ve seen rapid publication of avian flu papers – both in Chinese and International journals – and a willingness to point out some of the policies (live bird market sales, reliance on vaccination) that have exacerbated the situation.
Today Xinhuanet is carrying a fairly technical (for a newspaper) article written by the Institute of Microbiology, Chinese Academy of Sciences, that touches on many of China’s bird flu issues we’ve addressed here in the past. Namely:
- H7N9 (and to a lesser extent, H10N8) are circulating asymptomatically in Chinese poultry, but can produce severe illness and high mortality in humans
- Being asymptomatic in birds, these viruses are exceedingly difficult to track, or eradicate.
- These avian viruses continue to rapidly evolve, and reassort (primarily with H9N2), to produce new clades and even new subtypes.
- The most effective way to prevent human infection is to limit human contact with live birds, particularly through live bird market sales.
- Good biosecurity measures, and disinfection practices can reduce the risks on farms, but poultry farmers remain at risk.
- Migratory birds are considered an important part of the chain of infection between poultry farms, and it is important to maintain separation between wild birds and domesticated waterfowl or poultry.
First the (machine translated) article, then I’ll return with a bit more.
From the point of view of the origin of the avian influenza virus, we are faced with the virus mostly through by wild waterfowl - domesticated waterfowl - domesticated terrestrial birds, and ultimately infect humans process. In this process, such as H7N9, H10N8 for this type of virus itself is not any harm poultry, poultry does not cause serious disease, but after contact with an infected person will cause very severe symptoms and may lead to death. Present data suggest that the avian influenza virus H7N9 fatality rate is about 30%.
Epidemiological and molecular genetic analysis suggests the virus, H7N9 and H10N8 and other avian influenza viruses can be as fast transport and diffusion of poultry to humans through live animal; and able to use in chickens prevalent H9N2 subtype of avian influenza virus for rapid mutation, thereby increasing the difficulty of prevention. Therefore, the most effective way to avoid infection with avian influenza is to reduce contact with live poultry. In the spring of 2013 H7N9 high incidence of measures to close the live bird markets significantly reduced the growth of human infections. Currently, including Beijing, Hangzhou, including some of the city but also to effectively ban live animal control birds - who broadcast path.
Control of H7N9 virus from birds to human propagation path can effectively reduce the number of disease, but does not reduce the spread of the virus in poultry and can not control the variation of the virus. So for poultry practitioners still a huge risk. So how to reduce poultry virus? In poultry, the avian flu virus is mainly present in the digestive tract of sick poultry, and released into the environment through feces, other individuals through contact with infected poultry or drinking environment, consumption of contaminated water and food are infected. The survey found that, for the regular size of farms, the use of appropriate management and disinfection measures, thus poultry infection rate is very low. For most of the live bird markets and informal culture, lack of appropriate measures, causing the virus prevalent in poultry, a huge risk to public health. Guangdong Province recently introduced live bird markets is for the relevant management measures to reduce the infection rate considering the poultry live bird markets.
Take reasonable management and disinfection measures can effectively prevent the spread of bird flu virus in poultry, then there is no way to reduce the generation of new bird flu virus it? Historically generated almost everyone infected with avian influenza viruses from wild birds carrying the virus genes. Therefore, controlling the virus from wild birds into the poultry has become the key to reducing the bird flu virus produced. Wild birds into the poultry virus mainly through contact with domesticated waterfowl, by sharing living environment, water and food, viral infection by domesticated fowl waterfowl. Therefore, migratory birds season, waterfowl stocking reasonable arrangements to reduce contact with wild birds is an important means of reducing the bird flu virus into the poultry. At the same time, strengthen the waterfowl (ducks) and terrestrial birds (chicken) farming and trade isolation of avian influenza virus is an important way to prevent widespread infection in poultry.
Because of poultry and bird flu virus does not easily disappear, and will for a long period of time with the host symbiotic and pathogenic different hosts occasional cause even death. It should be said, to deal with bird flu that is the most effective way to control the number of infected poultry, cut off the transmission path of the bird flu virus. (Author: Institute of Microbiology, Chinese Academy of Sciences)
Interestingly, even though poultry vaccines have been the mainstay of bird flu control in China for the past decade, there is no mention of their application in the control of avian flu this article – or of culling, for that matter.
The article focuses essentially on creating two barriers 1) between wild birds and domesticated waterfowl or poultry and 2) between live birds and the public.
While culling is traditionally the preferred method for eradicating bird flu in much of the world, we’ve discussed previously the economic and political realities (see Food Insecurity, Economics, And The Control Of H7N9) that make that such an unpalatable option in China.
And poultry vaccines, while still in wide use, are falling out of favor because of the growing realization that over time and when pitted against a growing field of flu strains - they lose their effectiveness - and may actually be driving the creation of new vaccine escape viruses (see EID Journal: Subclinical HPAI In Vaccinated Poultry – China).
This article notes the role that the low path - but ubiquitous in Asian poultry – avian H9N2 virus has played in the development of these new viral threats, something we’ve discussed often (see The Lancet: H9N2’s Role In Evolution Of Novel Avian Influenzas & PLoS Path: Genetics, Receptor Binding, and Transmissibility Of Avian H9N2).
Over the past two years we’ve watched the emergence nearly a half dozen new avian flu subtypes in China (H7N9, H10N8, H5N3, H5N6, H5N8) - along with the creation of dozens of new clades of new and existing bird flu strains (see China: H5 AI Rising). And conditions appear ripe for the creation of even more in the future (see EID Journal: Predicting Hotspots for Influenza Virus Reassortment).
Whether these recommendations can be fully implemented, and will have the desired effect, is something we’ll have to wait and see. Attempts to close down, or regulate, live bird sales in China have been tried in the past and have met with great public resistance.
But at least, after 10 years of watching their bird flu problems escalate, the Chinese are openly discussing other control options.