Swine flu: "relatively mild"

Scientists see this flu strain as relatively mild

Excerpt:

"This virus doesn't have anywhere near the capacity to kill like the 1918 virus," which claimed an estimated 50 million victims worldwide, said Richard Webby, a leading influenza virologist at St. Jude Children's Research Hospital in Memphis, Tenn.

When the current virus was first identified, the similarities between it and the 1918 flu seemed ominous.

Both arose in the spring at the tail end of the flu season. Both seemed to strike people who were young and healthy instead of the elderly and infants. Both were H1N1 strains, so called because they had the same types of two key proteins that are largely responsible for a virus' ability to infect and spread.

The Centers for Disease Control and Prevention and the National Institutes of Health published genetic sequence data Monday morning of flu samples isolated from patients in California and Texas, and thousands of scientists immediately began downloading the information. Comparisons to known killers -- such as the 1918 strain and the highly lethal H5N1 avian virus -- have since provided welcome news.

"There are certain characteristics, molecular signatures, which this virus lacks," said Peter Palese, a microbiologist and influenza expert at Mt. Sinai Medical Center in New York. In particular, the swine flu lacks an amino acid that appears to increase the number of virus particles in the lungs and make the disease more deadly.

Scientists have identified several other differences between the current virus and its 1918 predecessor, but the significance of those differences is still unclear, said Dr. Scott Layne, an epidemiologist at the UCLA School of Public Health.

Ralph Tripp, an influenza expert at the University of Georgia, said that his early analysis of the virus' protein-making instructions suggested that people exposed to the 1957 flu pandemic -- which killed up to 2 million people worldwide -- may have some immunity to the new strain.

That could explain why older people have been spared in Mexico, where the swine flu has been most deadly.

Comment: Good news.