Southlanders: Prepare for a Longer-Than-Usual Flu Season
So how bad will this year’s influenza season be?
And how long will it last?
Acknowledging that such forecasts are risky business, public health officials predict a mild but perhaps longer-than-usual season--unless an “outlaw” virus comes calling.
In the Los Angeles area, the 1997-98 flu season “probably won’t be a wing-ding season” partly because it looks like the prevalent virus detected here, at least so far, is identical to or a “close relative” of last year’s, says Dr. Shirley Fannin, director of disease-control programs for the Los Angeles County Department of Health Services.
This year’s vaccine is meant to protect against influenza type A / Johannesburg, A / Nanchang and B / Harbin--the viruses thought to be most likely to surface.
But while the season might not be horrible, it could be longer than usual. “We’ve had an early start on our season this year,” Fannin says. The state’s first case of influenza A was confirmed in early November from a 3-month-old boy admitted to an Orange County hospital in mid-October. “That’s about a month before we usually see it,” Fannin says.
“Generally if you start early, you end late,” she adds.
In Southern California, flu season is generally considered to be from October to March, says Dr. Hildy Meyers, medical director of epidemiology for the County of Orange Health Care Agency.
But seasons have been shorter for the past several years, Fannin says.
“Last year was relatively mild. We didn’t see much activity after February.”
While the federal Centers for Disease Control and Prevention does not predict the severity of flu seasons, “we do have what we consider to be a normal flu season [so far],” spokeswoman Barbara Reynolds says. “But even in a ‘normal’ flu season, we can lose up to 20,000 people to influenza and its complications,” she says.
“It’s really very difficult to tell what a given flu season will be like,” says Robert Murray, an epidemiologist with the division of communicable disease control at the California Department of Health Services. That’s because influenza viruses are continually evolving and changing, making annual immunization crucial for those at risk.
Even annual immunization, however, isn’t foolproof. If an influenza virus surfaces that is dramatically different than those prevalent last season, the current vaccine may not protect against the new virus strain.
The virus strain that Murray and other epidemiologists have their eye on now is called influenza type A / Sydney. First detected in June in Australia and New Zealand, it has also surfaced on a cruise ship heading from New York to Montreal, in Hawaii and elsewhere. The new strain is related but different from the influenza A / Nanchang component in the current vaccine.
It’s not known how widely this new strain--so far not detected in the continental United States--will circulate this season nor how effective the current vaccine will be in protecting against it, according to a report published Nov. 21 in the CDC’s Morbidity and Mortality Weekly Report.
El Nin~o, the seasonal scapegoat, can only be indirectly blamed if this year’s flu season gets bad, says Meyers. “If we have a bad El Nin~o year, and people are inside more,” germs of all types are likely to thrive in such close quarters, she says.
As the season progresses, predicting the severity of an influenza season is guided by reports from physicians in the community and by school absenteeism. When the school absenteeism rate rises quickly (such as from one week to the next) to 25% or 30%, about three times the typical rate, influenza is the most likely cause, Fannin says.