Milder flu season winding down

April 02, 2009|By Frank D. Roylance | Frank D. Roylance,frank.roylance@baltsun.com

The 2008-2009 influenza season is not quite over, but Maryland health officials say it appears to have peaked and the number of new cases is on the wane.

"We expect lower levels of flu throughout the rest of the month of April, but it should finally be over by the beginning of May," said Rene Najera, an epidemiologist with the state Department of Health and Mental Hygiene.

This flu season has been milder than last year's, Najera said, and he credits the design of this year's vaccine.

"The vaccine strains were a better match" for the viruses actually circulating for most of this season, he said. "Last year, they were a complete mismatch."

Flu-related illness has killed three Maryland children this season. The state does not require that flu-related adult deaths be reported.

Baltimore-area hospitals reported that 172 adults and 194 children had been admitted for flu-related illness through mid-March, far fewer than were admitted last season.

This year's flu outbreaks began in Southern Maryland and spread to metropolitan Baltimore. From there, the illness moved to the Eastern Shore and finally to Western Maryland.

As good as this year's vaccine protection was, there are changes in the works for next season, according to the U.S. Centers for Disease Control and Prevention.

As the flu season has waned, B-type viruses have come to dominate, though the A-viruses had been more common for most of the winter. By the middle of March, the B-type became the majority - 52 percent of all new cases, the CDC reported. This year's vaccine had little or no impact on most of those B-viruses.

For next year's vaccine formulation, the World Health Organization and the U.S. Food and Drug Administration have agreed to once again include the protection against two A-viruses in this year's vaccine - two varieties of A Brisbane.

But the antigen for the B-viruses will be changed, from the B/Yamagata virus to the B/Victoria that came to dominate this season and showed only limited sensitivity - or none - to this year's vaccine.

Nationally, through mid-March, seasonal flu has killed at least 35 children, 53 fewer than during the full season last year.

But "we are not out of the woods yet," Najera said.

"We encourage residents to practice good hygiene year-round and to be ready to get in line to get flu shots come September and October."

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