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Route Of Shenzhen Bird Flu Infection Unclear

 

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The means by which a 39-year-old bus driver from the city of Shenzhen in Guangdong Province, China came to contract a fatal H5N1 infection remain unclear according to a report in today’s China Daily.

 

The victim, named Chen, was reported yesterday to have died after spending nearly a week in a coma at a local hospital (see Shenzhen Bird Flu Suspect Dies).

 

Early reports indicate he neither had contact with poultry, or had traveled outside of the city, in the past 30 days. First an excerpt from the Xinhua news report, then I’ll return with more.

 

Cause of bird flu death in S China still unclear

Updated: 2012-01-01 21:06
(Xinhua)

GUANGZHOU - Health authorities in south Guangdong province have yet to find the cause of the highly pathogenic H5N1 virus, commonly known as bird flu, that led to the death of a bus driver, a local disease control official said Sunday.

 

The 39-year-old man surnamed Chen in Bao'an district of Shenzhen was hospitalized for fever on December 21 and tested positive for the H5N1 avian influenza virus. He died of multiple organ failure Saturday afternoon, the Guangdong Health Department said in a statement.

 

The department also said that during the previous month prior to his fever, he had no direct contact with poultry and hadn't traveled out of the city.

 

Chen's wife said he had a habit of doing morning exercises every day near a wetland park and an artificial lake not far from his home, but "no proof has been found that his infection is connected with the migratory birds there," He Jianfeng, director of the Epidemics Studies Institute of the Guangdong Disease Control Center, said Sunday.

 

"We also don't know whether he had eaten poultry before he fell ill," He said.

(Continue . . .)

 

 

Determining the likely route of infection in a specific bird flu patient has always been tricky, and often the `official’ determination is based on circumstantial evidence.  

 

Direct contact with sick or dead birds has been the most common mode cited over the years, even in some cases where the aforementioned birds were not identified or confirmed to be infected with the virus.

 

And often, that was probably a reasonable enough assumption.  Occam's razor being – the simplest explanation is most likely the correct one.

 

Without specific regard to today’s case, it is worth noting that we’ve also seen serological evidence of subclinical, or asymptomatic infection with the H5N1 virus in China and in Thailand, and even among some people who were unlikely to have acquired it directly from poultry.

 

Last December, in Study: Subclinical H5 & H9 Infections In Humans, we saw a report out of China on the detection of antibodies to both H9 and H5 avian influenza viruses among a small number of villagers in and around Beijing, China.

 

The study was titled:

 

Infection With Multiple Avian Influenza Viruses in a Man Without Poultry-Handling Practices Suggesting an Increased Probability of Emergent Pandemic Influenza Virus in General Population

Peng Yang, Weixian Shi, Shujuan Cui, Yi Zhang, Xiujun Liu, and Quanyi Wang

 

 

In September of last year we saw a study that reported the results of this kind of serological testing conducted in a rural village in Thailand in 2008 (see Bangladesh To Share H9N2 Bird Flu Virus). 

 

Out of 800 villagers tested, the authors found 4.7% were seropositive for the Hong Kong H9N2 avian strain, 5.6% had antibodies to A/Thailand/676/2005 H5N1 bird flu, and 3.5% were shown to be seropositive to A/Thailand/384/2006 H5N1.

 

The implications of these studies are that human infection with these avian viruses – while still rare – is probably more common that current surveillance and reporting suggests.

 

And that opens the possibility, at least, that asymptomatic H5N1 infections could (in rare cases) provide a silent route of transmission of the virus.

 

Again, the evidence here is both scant, and primarily circumstantial. And there is no evidence to suggest sustained or efficient transmission.

 

For now, the H5N1 virus appears poorly adapted to human physiology. And while the concern is that, over time, that could change, it is also possible that this virus will never adapt fully to humans.

 

But with the recent laboratory successes in turning the H5N1 virus into a more easily transmissible pathogen (see The H5N1 Research Debate Goes On), there are renewed concerns in the scientific community that this avian virus may one day evolve enough to pose a serious pandemic threat to mankind.

Related Post:

China
H5N1
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