Flu season starts out early, deadly

The flu season is off to an early and deadly start in Wisconsin, with 26 hospitalizations and four flu-related deaths reported here already, according to the state Division of Public Health.

Public health officials aren't sure what's behind the uptick in hospitalizations so early in the season.

A previously seen influenza A H3N2 strain - the dominant strain so far this flu season - appeared to be a good match for the current vaccine, said Paul Biedrzycki, director of disease control and environmental health for the Milwaukee Health Department.

"However, you can't rule out a possible mutation in the flu virus," Biedrzycki said Monday. "Flu viruses change unexpectedly and arbitrarily."

During the last two to three flu seasons, no flu-related hospitalizations were reported before January, said Tom Haupt, the epidemiologist at the Wisconsin Division of Public Health in charge of influenza surveillance.

On Monday alone, 14 hospitalizations were reported to the state, including four pregnant women who did not get flu shots, Haupt said. Statewide, between Oct. 5 and Friday, 113 laboratory-confirmed influenza cases had been reported, compared with seven cases at this time last year.

Haupt urged other pregnant women to get the flu vaccine, which takes about two weeks to provide full protection.

This is the earliest flu season in nearly a decade, since the winter of 2003-'04, which turned out to be one of the most lethal in about 35 years, the federal Centers for Disease Control and Prevention reported Monday.

During the 2003-'04 flu season, more than 48,000 people died nationwide. The dominant flu then is the same dominant strain seen so far this season - A/H3N2 (the same subtype as Hong Kong flu) - according to the CDC. This influenza strain generally causes more severe flu seasons. It's related to the Hong Kong pandemic strain, which caused nearly 34,000 deaths in the United States in 1968 and 1969. That was the last pandemic before the 2009 swine flu pandemic (also known as H1N1).

Scientists are now investigating whether the genes of the seasonal A/H3N2 could have mutated, resulting in a more severe and/or more easily transmissible flu not covered exactly by the flu vaccine developed six to eight months ago, Biedrzycki said.

"It has to be a change in the bug or a change in susceptibility, which could include low vaccination rates," he said.

With the flu season starting earlier this year, it also may peak earlier - around the holidays, public health officials said.

Local and federal public health officials still stress that a flu shot provides the best protection.

"If there was a change in the virus, there may be some cross-protection from the current vaccine and it may prevent increased transmission to very vulnerable populations" - the young, pregnant women and elderly, Biedrzycki said.