Scientists still figuring out cause of swine flu

Scientists have yet to figure out how the swine flu virus spreads, or what makes it lethal, which could continue spreading or fizzle out, they said.

 

Sometime in the last few years, as the world's attention was focused on the bird flu that killed hundreds of people in Asia, another bird flu strain infected pigs. It mixed with two kinds of flu that are endemic in swine and a fourth that originally came from people.

 

 

Scientists said Sunday (Apr 26) they are unable to predict what this new swine flu will do next.

 

Epidemiologist Scott Layne said inspecting the virus itself is of little help, since scientists have yet to identify which features help it spread or kill.

 

Among threats to public health, flu poses an unusual challenge. People, pigs, birds and horses have developed unique strains of flu, which can easily mix and match into new strains that the human immune system is ill-equipped to recognise.

 

And since the eight genes that form all Type A flu viruses - the most dangerous kind - are made of RNA instead of DNA, they do not copy themselves reliably and are prone to further mutation.

 

Flu research has accelerated since the Asian bird flu spread to humans in 1997. But the more scientists study it, the more questions they have.

 

Yet for all its destructive power, the flu virus is a straightforward organism. Its outer shell is studded with a protein called hemagglutinin that allows flu particles to attach to cells lining the respiratory tract.

 

The virus then takes over the host cell and uses it to make hundreds of copies. Those new flu particles use another surface protein, neuraminidase, to break off from the host so they can search for new targets.

 

There are 16 types of hemagglutinin, or H, and nine of neuraminidase, or N; the combination gives a flu strain its name. The swine flu involved in this outbreak is an H1N1 variety.