Mar. 3--Call it the flu season that wasn't.
Despite the cold and snow, the seasonal flu bug that strikes during winter months is absent.
"It's been practically nonexistent," Guillermo Cole, spokesman for the Allegheny County Department of Health, said Tuesday. "It's like a no-show flu."
Seasonal flu typically thrives this time of the year, with outbreaks peaking as late as March.
This year is different, with outbreaks of the nearly forgotten swine flu -- or H1N1 influenza -- occurring in fall.
Swine flu infected about 57 million people nationwide, instead of the usual 25 million, according to the Centers for Disease Control and Prevention in Atlanta.
Doctors' offices and hospital emergency rooms, however, are reporting little activity from seasonal flu -- a different strain that can affect up to 20 percent of the population.
Cole said the Health Department has received no recent flu reports from hospitals. The state Department of Health reported 97 cases of seasonal flu through Feb. 20, compared with 2,710 during the same period last year.
"We've seen very little to none," said spokeswoman Stacy Kriedeman, noting that department numbers provide only a partial picture of flu activity.
At Children's Hospital of UPMC in Lawrenceville, doctors said they haven't found a positive culture of either H1N1 or seasonal flu since December -- even though patients with flu-like symptoms overwhelmed the hospital in October. Doctors at University of Pittsburgh Medical Center and Allegheny General Hospital said they are seeing almost no patients with seasonal flu.
"The typical season of the flu was completely overshadowed by the H1N1 flu," said Dr. Marc Itskowitz, an AGH internist with offices in the North Side.
Experts said pinpointing the reasons is impossible but offered some contributing factors.
They said it's usual for influenza outbreaks to occur in unpredictable waves and that new viruses can peak at unusual times of the year, such as summer or fall. In addition, people infected with one respiratory virus have a lower chance of catching another.
"I'm not sure anyone knows why the numbers are low," said Dr. Marian Michaels, an infectious-disease expert at Children's Hospital. "When one virus is very active in the season, it seems to be the majority of what we see, and other viruses are not as prevalent."
The attention given to H1N1 might have helped curb the spread of flu, others said. Worried parents sought vaccinations for children -- a high-risk group that spreads viruses in closed quarters, such as schools. People paid attention to public-health campaigns that urged them to wash their hands and cover their mouths when coughing or sneezing.
"The message has been driven home about the importance of hygiene, hand-washing and respiratory etiquette," Cole said. "I see it all the time. It's something that really stands out. That tells me that this message is sinking in, and people are now translating the message into action."
The low level of flu activity, though, doesn't rule out the possibility of outbreaks in the spring -- including swine flu, experts said.
In Pennsylvania, authorities have confirmed nearly 11,000 cases of swine flu so far. With nearly 2,000, Allegheny County reported the highest number of all counties.
"I don't think people have to be worried, " said Michaels at Children's Hospital, "but there's reason to always be cautious and for vigilance to be maintained."
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