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Public Health Officials Investigate Change In Common Flu Strain

For release: Immediate    Mar. 28, 2011
Contact: Julie Henry, (919) 707-5053

RALEIGH — Flu cases are on the decline across the state, but state and federal health officials continue to examine virus activity during this year’s flu season. The N.C. Division of Public Health is notifying physicians in North Carolina of an ongoing investigation with the U.S. Centers for Disease Control and Prevention (CDC) into a cluster of influenza B viruses from North Carolina that appear to show less responsiveness to a common antiviral drug than typical flu viruses.

Lab tests conducted by the CDC indicate that the antiviral drug oseltamivir, also known as Tamiflu, has slightly less effect on these particular viruses than on influenza B viruses without the change. The reason appears to be a genetic change in the viruses that has not been seen in samples from other states.

“These particular viruses are less sensitive to the drug in the lab, but they are not resistant,” said Dr. Zack Moore of the N.C. Division of Public Health. “We want to assure physicians and their patients that antiviral drugs remain an effective treatment for influenza.”

Moore emphasized that while influenza B infections have been common during this flu season, it does not present a greater risk to individuals than other flu strains. The best way to prevent the spread of any influenza virus is to wash your hands, cover coughs and sneezes, and stay home if you are sick.

Thirty-one viruses with this genetic change were collected from 92 samples from North Carolina patients between November 2010 and February 2011. Most of the patients had typical flu symptoms and recovered after several days; one patient who had severe underlying immune problems died shortly after being diagnosed with influenza.

CDC is testing more influenza B viruses from North Carolina and surrounding states to determine whether the same genetic change can be found in other influenza B viruses from North Carolina or elsewhere in the country. The CDC investigation also includes a telephone survey of North Carolina residents who tested positive for influenza B to gather information about their treatment.

Because the importance of intermediate sensitivity to oseltamivir in these samples is not yet clear, the N.C. Division of Public Health and the CDC are advising physicians to follow existing antiviral guidelines, but to consider this new information when caring for North Carolina patients who are hospitalized with severe influenza B infections.

Influenza B virus infections have accounted for almost half of all specimens that tested positive for influenza at the State Laboratory of Public Health since October. Public health officials plan to monitor this situation closely throughout the year and provide updated information as available to North Carolina physicians.

 

 

 

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