Wednesday, September 28, 2005

Flu news

From National Geographic...

There are three types of influenza–A, B, and C. Type C viruses trigger mild respiratory illness or, sometimes, no symptoms at all. Type A and B viruses, on the other hand, can cause epidemics in humans. They result in an average of 36,000 deaths and 114,000 hospitalizations in the U.S. each year. While type B viruses are normally exclusive to humans, type A viruses are also found in birds, pigs, horses, seals, whales, and other animals.

Type A flu viruses, H5N1 for example, are named for two proteins on their surface. The H stands for hemagglutinin, which helps a virus break into the cell. The N stands for neuraminidase, which helps it break out. These proteins also act as antigens. If the body recognizes them, its immune system can mount a defense.

All type A viruses attack human cells in the same way. Once the virus enters the body, hemagglutinin binds the virus to the cell surface. Then the cell surface folds in around the virus. The virus sinks into the cell until it is completely engulfed. Because the cell membrane wraps around the virus, it creates a bubble-like compartment called an endosome. A change in pH in this compartment changes the structure of the hemagglutinin and allows the viral contents to move into the cell's inner fluid, or cytoplasm.

Once there, the virus has free reign. The virus's genetic material, which is split into eight different segments, is copied in the nucleus. After being copied, the segments return to the cytoplasm, and with the help of neuraminidase, can reassemble, leave the cell, and attack new cells. However, since each of the eight segments is copied separately, if two different viral strains infect the same cell, then their segments can mix and match, ultimately forming new viruses.

Hugh Hewitt asks, "Are we paying attention yet?"

1 comment:

Elsa said...


Here in Holland we are certainly not prepared for dangerous virusses which could cost the life of many human beings.
They really do understimate the danger of it. But that is common; government and other responsible people are talking about what could happen but no action or precautions are taken.

We live in this small country with 16 million people, can you imagine what can happen within a rather short time?