Photo Credit CRIENGLISH
When it comes to variety, avian influenzas come in more flavors than you’ll find in a Baskin-Robbins store. Which explains why in the past couple of months our attentions have been divided between H5N1 in Cambodia and Indonesia, H7N9 in Mainland China, an upstart H10N8 (again in China), and now H5N2 in Hebei Province, China.
While we worry most about H5N1 and H7N9 – primarily because both have been shown to produce severe illness and even death in humans – all H5 and H7 varieties are of concern, since these subtypes have a history of morphing from low-pathogenic strains to highly pathogenic strains if not controlled.
Which is why all H5 and H7 outbreaks are reportable to the OIE, and quarantine and immediate culling are the preferred course of action.
Yesterday China reported an outbreak of H5N2 at a poultry farm in Baoding City, Hebei Province. Reports today indicate that more than 120,000 birds have been culled, and that 11 people who were in direct contact with the poultry have been placed in isolation (and probably given Tamiflu ®), but none have shown signs of infection.
First a report from Sina News, then I’ll be back with more on the history of H5N2
(CNA Taipei 22 (Xinhua)) Hebei Baoding Nanshiqu officials said today, raising the local chicken farm H5N2 bird flu has been effectively controlled occurred, 11 were in direct contact with the relevant chickens were isolated observation, it was not found infected.
China News Service reported, Baoding Nanshiqu Agriculture Secretary Zhang Guang pointed out that, in addition to the above measures, culling chickens participating Nanshiqu work were monitored twice daily, were not unusual. Meanwhile, the official has the region's comprehensive agricultural and sideline products and fragmented market of live poultry trade to clean up and banned.
Zhang also said that the official and farm stocks of eggs into the marketing ruin handling , disposal of tracing the source of the product sold. Meanwhile, the live poultry within 3-5 km range chicken farm near the outbreak, have been carried out culling.
H5N2 outbreak was discovered south downtown Baoding Zhu Village tiger phoenix chicken farm was built in 1992, is a self-employed business , keeping more than 120,000 laying hens only, no chickens. 4000 chickens on the 17th because the epidemic of death was November 27 to buy from overseas. 1021222
It should be noted that we’ve seen both HPAI (Highly pathogenic) and LPAI (Low Pathogenic) H5N2 outbreaks in the past, notably in Taiwan, Canada, the United States, Korea, Japan, and Mexico.
The isolation (and usually, antiviral treatment) of those who have been in direct contact with infected birds is standard procedure, and should not be viewed as being particularly alarming. While not normally thought of as a serious threat to public health (see WHO: Human Risk From H5N2 Is Low), we have seen some limited evidence of H5N2’s ability to infect humans in recent years.
Eighteen months ago, in Taiwan: Three Poultry Workers Show H5N2 Antibodies, we looked at a report that three poultry workers and officials working in animal quarantine have tested positive for antibodies for the H5N2, but all remained healthy and asymptomatic (note: refer to article for other possible causes of seropositivity)..
Some earlier H5N2 studies include:
J Epidemiol. 2008;18(4):160-6. Epub 2008 Jul 7.
Ogata T, Yamazaki Y, Okabe N, Nakamura Y, Tashiro M, Nagata N, Itamura S, Yasui Y, Nakashima K, Doi M, Izumi Y, Fujieda T, Yamato S, Kawada Y.
Arch Virol. 2009;154(3):421-7. Epub 2009 Feb 3.
Serological survey of avian H5N2-subtype influenza virus infections in human populations.Yamazaki Y, Doy M, Okabe N, Yasui Y, Nakashima K, Fujieda T, Yamato S, Kawata Y, Ogata T.
While these reports are suggestive of prior H5N2 human infection – particularly among poultry workers – we haven’t seen any good evidence that it has produced significant or serious human illness.
The caveat being, that up until the emergence of H7N9 in March of this year, H7 avian flu viruses had been generally regarded as posing a minor threat to human health, and until this past week, we’d never seen a human infection with the H10N8 virus.
With influenza viruses, the only constant is change. What may be relatively benign today, may become virulent or increase its host range tomorrow.
Which makes the rapid and intense response to bird flu outbreaks – such as we are seeing with H5N2 in China right now – the prudent course of action.