NEW YORK, Sept 05 (Reuters) -- Summer's almost over, and -- unfortunately -- it's time for those living in North America to begin thinking about flu season. The good news is that the predominant type of flu strain expected to circulate in the U.S. this year -- influenza B -- generally doesn't cause as many fatalities as the type that circulated last year, influenza A, according to the Centers for Disease Control and Prevention (CDC). An average of 20,000 people die every year of flu-related causes, but more deaths occur in years when influenza type A is the predominant virus in circulation.
"It's very hard to really predict what's going to happen with any great precision," said Nancy Arden, an epidemiologist with the CDC in Atlanta. "But we do think that we will probably see more influenza B than we have in recent years." Influenza B hasn't been found at high levels since the 1992/1993 flu season, and at the end of last year's season, the virus type began edging out influenza A as the main cause of flu, which is characterized by fever, cough, stuffy nose, muscle aches and fatigue. Flu season usually runs from October to April in the U.S.
An influenza vaccine is now available which incorporates three different influenza strains, including two A types and one B strain. Such vaccines are usually 70% to 90% effective in preventing illness in healthy adults.
CDC officials say that in September, health care providers should begin to offer this year's flu vaccine to those at high risk. People should try to be vaccinated before the middle of November, as the vaccine takes one to two weeks to take effect, said Arden.
"We can't say exactly what is going to happen this winter and people should be prepared and get their flu vaccine if they are at high risk," she said. Those at high risk include people over 65 and those with chronic health conditions, such as chronic cardiovascular or lung disorders; children with asthma; and women who will be in the second or third trimester of pregnancy during flu season. Vaccination is also recommended for health care workers and those who have frequent contact with people at high risk for flu complications.
"People who are at high risk of having complications should take vaccine every year and should not think 'well, maybe I cannot take the vaccine this year because this news story I read said this is going to be a mild season,'" Arden said. "We do expect type A to circulate -- and again, even though type B is not associated with excess mortality, it can result in complications requiring hospitalization, and it also causes just as much disruption of work and school as any other type of influenza."
For an influenza update, call the CDC's Voice Information Service at 1-888-232-3228 or check out the CDC's Web site at http://www.cdc.gov/ncidod/diseases/flu/weekly.htm.
SOURCE: Morbidity and Mortality Weekly Report (1997;46;815-818)
