Studies: Avian Flu Can't Be Coughed Into Open Air

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I'm a little confused... FOX seems to be a be almost " fair and balanced " on

this . UncBob

 

http://www.foxnews.com/story/0,2933,188800,00.html

Studies: Avian Flu Can't Be Coughed Into Open Air

Wednesday, March 22, 2006

By Bjorn Carey

 

OAS_AD('Frame1'); More than 100 people have died from infection

with the avian flu virus , but so far it can't hop from person to person. That's

why there has been no global outbreak among humans.

Scientists are not quite sure why the virus, called H5N1, has yet to mutate

into a strain that can be transmitted between humans.

One study found that this avian strain can't bind to human cells. Another

study, released last week, suggested one key mutation is all that is keeping the

avian flu out of the human population.

Click here to go to the FOXNews.com Bird Flu Center.

Now two independent research teams have revealed that bird flu virus can bind

to human lung cells, but it attaches too deeply in the respiratory tract to be

coughed up and spread.

One of the teams also found that infection could lead to increased risk of

viral pneumonia.

The two studies, both announced today, are detailed in the March 22 issue of

the journal Nature and the March 23 issue of Science.

Influenza most commonly spreads in liquid droplets made airborne by coughing

or sneezing. You can also be infected by touching surfaces where droplets have

landed — such as counter tops or doorknobs — and then touching your mouth or

rubbing your eyes.

Influenza viruses, of which there are many strains that evolve constantly,

require access to host cells in order to reproduce and spread. To gain access,

surface molecules on the virus must match receptors on the surface of the

potential host's cells.

The new research reveals that cells with H5N1 avian flu receptors are

prevalent deep in the lungs of people who have died from infection, usually

after direct contact with infected birds.

The virus can readily enter and replicate within lung cells called type II

pneumocytes. These cells are important for repairing lung tissue and producing

molecules necessary for normal lung function.

" But these receptors are rare in the upper portion of the respiratory system, "

said University of Wisconsin-Madison research Yoshiro Kawaoka, who led the study

in Nature. " For the viruses to be transmitted efficiently, they have to multiply

in the upper portion of the respiratory system so that they can be transmitted

by coughing and sneezing. "

To do this, the bird flu viruses must undergo further genetic alterations and

borrow cell surface receptors from a human influenza strain.

For these gene swaps to occur, a bird or human (or intermediary host such as a

pig) must be infected with both the avian H5N1 and a human influenza strain,

researchers say. That way, the two strains can share genetic material to make a

new variety.

" No one knows whether the virus will evolve into a pandemic strain, but flu

viruses constantly change, " Kawaoka said. " Certainly, multiple mutations need to

be accumulated for the H5N1 virus to become a pandemic strain. "

Although millions of poultry in Asia have been infected with the H5N1 virus,

there have been fewer than 200 confirmed human infections.

" However, in the rare cases that human infection has occurred, the fatality

rate is high, and the primary lesion is pneumonia, " Science study co-author

Thijs Kuiken of the Erasmus Medical Center in Rotterdam, the Netherlands, told

LiveScience.

Pneumonia is the generic medical term for an infection or inflammation of the

lungs. It can be caused by bacteria, viruses, fungi, and other microorganisms.

Because the H5N1 virus targets cells responsible for repairing damage to the

lung lining, seeping wounds are slow to heal.

Viral pneumonia is generally not very serious to healthy adults, but it can be

deadly for very young and very old patients as well as those with impaired

immune systems.

2006 Imaginova Corp. All Rights Re

 

 

 

 

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