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China Seeks To Reassure On Bird Flu

 


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Guilty as charged?     Photo Credit – FAO

 

# 6047

 

The news wires this morning are filled with reports on the investigation into the death of a Shenzhen bus driver late last week from the H5N1 virus (see Shenzhen Bird Flu Suspect Dies).

 

The substance of most of these reports appear to be based on the details released in a Xinhua News Service report overnight.

Xinhua is the official news service (some would say press agency) of the Chinese government.

 

The gist of the report (linked below) is that health officials have reportedly identified the H5N1 strain, and have determined through genetic analysis that while pathogenic in humans, it is `not transmissible’.

 

First the Xinhua report (emphasis mine), then I’ll return with a little more.

 

Authorities identify virus leading to Guangdong bird flu death

Source: Xinhua  |   2012-1-2  HEALTH authorities in south Guangdong province have identified the type of the virus that led to the death of a bus driver, but the cause of the bird flu remains unclear, a local disease control center confirmed today.

 

The receptor of the virus, a highly pathogenic H5N1, is poultry, according to a statement released by the Shenzhen Disease Control Center.

 

Though it is highly pathogenic to human beings, the virus can not spread among people, the center said in the statement, adding that there is no need for Shenzhen citizens to panic.

 

Genetic analysis also indicated that the virus was spread directly from poultry to human, according to the statement.

 

A 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. Chen died of multiple organ failure Saturday afternoon.

 

Health authorities are trying to figure out where Chen acquired the virus.

 

The Guangdong Department of Agriculture announced Saturday that no epidemic of bird flu among poultry had been reported in the province.

 

This reassuring missive – complete with the standard admonishment `not to panic’ – is unfortunately both contradictory, and lacking in detail. 

 

We are told in two places that the route of infection is unclear, and in another that genetic analysis shows it was from direct contact with infected poultry.

 

But at the same time we are assured by the Agriculture Department that no outbreaks of H5N1 have been reported in poultry anywhere in the Province.

 

The `receptor’ of the virus – by that I assume they mean the RBD (Receptor Binding Domain) – is stated as being `poultry’. 

 

I’m assuming they mean avian in nature (an affinity for alpha 2,3 receptor cells).

 

A virus’s ability to bind to specific cells is controlled by its RBD or Receptor Binding Domain; an area of its genetic code that allows it to attach to, and infect, specific types of host cells.

 

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(A Very Simplified Illustration of RBDs)

Like a key into a padlock, the RBD must `fit’ in order to open the cell to infection.

 

Humans, unlike birds, have mostly alpha 2,6 receptor cells in their upper respiratory tract, making it difficult for avian viruses to attach. Humans do have some a2,3 receptor cells deep in the lungs and in their gastrointestinal tract.

 

The declaration that the `virus can not spread among people’ would therefore seem a bit strong, as we’ve seen limited transmission of avian-adapted viruses among humans in the past.

 

That this virus is not yet well adapted to human physiology - and therefore unlikely to be spread from one human to another - is probably a more reasonable assessment.

 

The lack of additional cases thus far in the province is obviously a good sign, and if that trend continues, would lend credence to the government’s claim that this is not an easily transmissible strain.  

 

But a lack of scientific detail - along with an overly reassuring tone and China’s chequered history on the reporting of previous disease outbreaks - makes it difficult to come away from this report completely assuaged.

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China
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