Bird flu mutation sparks concern Genetic tweak makes virus favour human nose and throat.

news@nature.com ^ | 13 January 2006 | Declan Butler

[neverdem]

Researchers have sequenced the bird flu viruses that killed two people in Turkey in early January, and say that one of them contains a worrying mutation.

This genetic tweak can make the H5N1 virus more adapted to humans than to birds, and more adapted to the nose and throat than to the lungs. This latter effect could help to increase the chances of bird flu being transmitted between people, researchers say.

They add that many more mutations would probably be necessary before the virus is capable of sparking a full-blown pandemic, in which disease spreads like wild fire from person to person.

The samples of H5N1 virus, taken from the first two victims who died of bird flu in Turkey, were sequenced at a World Health Organisation (WHO) collaborating centre at the National Institute for Medical Research in London, UK. The results were announced on Thursday 12 January, along with confirmation of two new cases: bird flu has now also struck Sanliurfa Province, near Turkey's southern border with Syria, and Siirt Province, in the eastern part of Turkey.

The total number of reported human cases has now reached 18 in less than two weeks, three of which have been fatal.

In a bind

The WHO has released details of only one of the mutations found in the viruses. This genetic change results in a substitution of the amino acid serine by another amino acid, asparagine, at a specific position in one of the virus's proteins; a protein that helps the flu virus to bind to receptors on host cells.

This mutation has been observed twice before: in a father and son in Hong Kong in February 2003, and in one fatal case in Vietnam last year. It is known to increase the affinity of the virus for human receptors over poultry ones.

Until samples from the remaining cases are sequenced over the coming week, it is unknown how many of these came from viruses with the same mutation. If many prove to have the same tweak, this may help to account for the relatively large size of Turkey's rapid outbreak. The WHO's current explanation for the spate of cases is simply that people are bringing chickens into their homes during the harsh Turkish winter.

Nose and throat

The mutation also has a secondary effect, which may be more worrying.

There are two subtypes of receptors in the human respiratory tract: alpha 2.3, which occurs mainly in the lower respiratory tract; and alpha 2.6, which occurs mainly in the nose and throat. Human flu viruses typically show a preference for the 2.6 receptors, whereas H5N1 strains typically prefer 2.3.

This is good news for those worried about bird flu, since human-to-human transmission is thought to be more likely via droplets coughed from the nose and throat than from infections lower down. But the mutation found in the Turkey viruses is also known to be able to increase the affinity for H5N1 to the 2.6 receptors, points out Sylvie van der Werf, head of the Laboratory of Molecular Genetics of Respiratory Viruses at the Pasteur Institute in Paris, France.

Van der Werf adds that this affinity will, however, be affected by other genetic changes in the virus, which at present are an unknown factor.

Multiple mutations

Thankfully, one mutation alone is unlikely to lead to efficient human-to-human transmission. The genetic changes that would allow this to happen are poorly understood, but are thought to require an exact combination of changes in multiple genes.

"Adaptation to humans is a polygenic trait. It requires mutations in each of the eight segments of the virus's genome. Every one has to be correctly optimized to ensure human-to-human transmission," explains Edward Holmes, who is studying virus evolution at Pennsylvania State University in Philadelphia. "You are talking multiple mutations across the entire genome."

That's an improbable, but not impossible event.

Researchers continue to examine the genome of bird flu viruses, and are taking measures to stop the spread of disease among birds and people in Turkey.

A mutated strain of bird flu has genetic make up that increases its chance of transferring to people.

doi:10.1038/news060109-14

[neverdem]

Turkish Agriculture Ministry employees collect poultry for culling in the village of Cebeci, Turkey © WHO

Bird Flu Mutation Of Concern, Experts Say

They chased strays up and down the slippery, muddy hills and ravines, and when they caught one, they stuffed it into a plastic bag. Signs around the neighborhood read, "This District Has Chicken Plague."

Workers dressed in protective gear threw the bags into green containers that looked like large garbage cans. A sanitation worker attached a blue tube from a tank of carbon dioxide to the airtight container, opened the valve and killed the birds. "We prefer to say we are putting them to sleep," said Hikmet Karacay, an Agriculture Ministry official.

Residents, most of whom raised chickens as a sideline to collect the eggs, cooperated. "The real problem is the children," said Gilsen Kaya, who has two daughters. "They like the chickens. They are like pets. That's why it's better to do it at night, when they don't witness the whole thing."

[Alter Kaker]

Utter nonsense. We all know evolution is impossible! We have nothing to fear from mutating pathogens. Nothing!

/s
(a tag I wish I didn't have to append)

[txhurl]

Level 5?

[neverdem]

Level 5?

I don't know. I can't say if this mutation is critical. Our ignorance could be. I'm just a humble FP doc.

[Judith Anne]

I can't remember the exact definitions of the levels, but I think this could be level 4...

[StAnDeliver]

[ex-Texan]

Virus spreading from human to human by means of cough or sneeze 'droplets' is level four. (Airborne virus). Level four means "efficient human-to-human transmission." Level FIVE is evidence of a full blow pandemic. China has been covering up evidence of pandemic for months by using martial law and news black outs. People reporting the truth have been imprisoned.

[ex-Texan]

If avian flu strikes poultry farms, infecting chicken, KFC may face very trying times.

[joesnuffy]

Short Tyson

[joesnuffy]

We'll all be rich dead men...as we used to say on the Soo Line.

[TFMcGuire]

The genetic variant of the virus may be less destructive to lung tissue that the "Original" strain.

While its ability to be passed from person to person may be increasing, its virulence may be decreasing.

[TFMcGuire]

Sad choice of terms.

Mutation is a well known genetic phenomenon.

Beneficial mutations are not.

I suspect that the term mutation here is used in its general sense of any kind of change in genetic material.

Many microorganisms have the ability to pick of free DNA/RNA in, say, an infection environment and incorporate it into their own genetic code.

This makes no case for the twilight zone macroevolution the modern pseudos teach.

[From many - one.]

Very entertaining, but flapdodle nontheless.

[txhurl]

Aren't you the one whose girlfriend had to dump you over the flapdoodle thing?

[From many - one.]

Loser advertises by producing ad hominems.

[TheLion]

"China has been covering up evidence of pandemic for months by using martial law and news black outs. People reporting the truth have been imprisoned.

Any links?

[txhurl]

No! that was not an attack at all: I just seem to remember something funny you said along those lines that made me laugh, possibly years ago.

These virii threads go way back in time.

[From many - one.]

Ok. Next time 'll say codswallop and seewhat you make of that. ;->

[ex-Texan]

A few reports are posted Here. Recombinomics has been reporting China's efforts to hide deaths from bird flu for months. I have been posting reports on China when I run across them. Look on the older bird flu threads. Beijing's efforts to clamp down on news reports began during the SARS epidemic. Hundreds of patients were arrested and hidden away in military hospitals. Look up old SARS reports here. Chinese reporters and bloggers have been arrested and thrown into prison. Censorship and martial law is a fact of life in China today.

[Tolerance Sucks Rocks]

BTTT!