The truth about swine flu: Separating fact and rumor

Swine flu is spreading: 292 U.S. deaths have been confirmed since Aug. 30, and seven times that number are suspected. But rumors about the illness and the vaccine to prevent it are spreading even faster.

Some recommendations that were legitimate a few months ago have been superseded by larger studies, giving some people reason to doubt the latest advice.

There is general agreement among experts about treating and preventing the disease, however. The following is based on the most up-to-date information.

Question: What's the difference between flus?

Answer: "Seasonal flu" actually consists of several strains. The Type A strains change slightly every year, which is why flu vaccine is reformulated annually. The population retains some immunity, however, so most people don't get seriously ill.

Every once in a while, a major genetic shift introduces a Type A strain to which few people have any immunity. This happened three times in the last century, causing the pandemics that began in 1918, 1957, and 1968. As the population developed immunity over several years, the pandemic strains settled into a seasonal flu pattern.

A new pandemic strain appeared again in spring 2009 and is now building toward its first full season.

Q: Is swine flu more dangerous than seasonal flu?

A: The new flu appears to carry about the same overall risk of complications and death as seasonal influenza. But far fewer people have immunity. An estimated 36,000 Americans a year die from complications of seasonal flu, so if twice as many get sick, there could be 72,000 deaths.

Q: Why are more young people dying from swine flu?

A: Older people have more immunity, apparently because the new flu is distantly related to strains that circulated through much of the last century.

Younger people with less immunity get the most exposure to this flu, spreading it quickly in school. "They are close to each other, they wipe their nose on their hands, they touch their friends," said Neil Fishman, an infectious disease specialist at the Hospital of the University of Pennsylvania.

Eighty-six children under 18 have died of swine flu, half of them since Aug. 30, the U.S. Centers for Disease Control and Prevention reported on Friday.

Q: Are pregnant women dying in large numbers?