Flu looks less deadly than previous viruses

Scientists studying the swine flu virus are coming to the consensus that this hybrid strain of influenza – at least in its current form – is not shaping up to be as fatal as the strains that caused some previous pandemics.

In fact, the current outbreak of the H1N1 virus, which emerged in San Diego and southern Mexico late last month, may not even do as much damage as the run-of-the-mill flu outbreaks that occur each winter.

“Let’s not lose track of the fact that the normal seasonal influenza is a huge public health problem that kills tens of thousands of people in the U.S. alone and hundreds of thousands around the world,” said Dr. Christopher Olsen, a molecular virologist who studies swine flu at the University of Wisconsin School of Veterinary Medicine in Madison.

Flu viruses are known to be notoriously unpredictable, and this strain could mutate at any point – becoming either more benign or dangerously severe. But mounting preliminary evidence from genetics labs, epidemiology models and simple mathematics suggests that the worst-case scenarios are likely to be avoided in the current outbreak.

“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 Research Hospital in Memphis, Tenn.

The U.S. 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 began downloading it immediately. 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 Mount 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.