Last Flu Season Was Mild, But Child Deaths Worrying

(Page 2)

Despite the troubling news that such dual infections may be on the rise, the past season's flu statistics were relatively positive, Katz said.

"Data from the last flu season provide mostly good news," he said. "The number of cases was never unusually high. The strains were mostly of the expected varieties, and vaccine composition was just right. The death toll from complications of influenza was a bit lower than average."

The reasons for the milder flu season aren't clear, said Dr. Marc Siegel, an associate professor of medicine at New York University School of Medicine. "It could be increased surveillance and improved care and more awareness of what influenza can do," he said. "It may also be a less virulent strain of the virus."

Katz noted that, even in a good year, the average number of deaths from flu in the United States totals about 30,000, mostly among the elderly.

During the 2006-07 flu season, the influenza A (H1) virus was most common in the United States, but the A (H3) virus was found to be more common late in the season, according to the CDC.

For the 2007-08 vaccine, the U.S. Food and Drug Administration's Vaccines and Related Biological Products Advisory Committee has recommended that the trivalent flu vaccine contain A/Solomon Islands/3/2006-like (H1N1), A/Wisconsin/67/2005-like (H3N2), and B/Malaysia/2506/2004-like viruses, the CDC reported.

The influenza A (H3N2) and influenza B components remain the same for the new vaccine. These recommendations were based on antigenic analyses of recently isolated influenza viruses, epidemiologic data, vaccination studies in humans, and the availability of vaccine strains and reagents, the CDC said.

Last season, around the world, influenza A (H1), A (H3), and B viruses were most common. In Africa, small amounts of influenza A and B were seen. In Europe and Asia, influenza A (H3) virus was most common, but low levels of A (H1) were seen. Influenza B viruses were seen at lower levels in Asia and Europe but were most common in some countries, according to the CDC.