HealthDay News — The H3N2 strain of influenza, a strain that is associated with double the death rates than that of other flu strains, is circulating most widely this season, according to officials from the United States Centers for Disease Control and Prevention (CDC).

Additionally, about half of the H3N2 viruses detected by CDC researchers so far appeared to have mutated, genetically drifting away from the virus strain including in this year’s flu vaccine.

CDC officials are urging health-care providers to use antiviral drugs as soon as possible for any suspected flu cases. The agency recommends that clinicians do not wait for the results of a flu test before starting patients on antiviral drugs, as they are most effective when given within two days of the onset of symptoms.

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Clinicians are urged to aggressively use antiviral drugs in suspected flu patients who are:

  • Aged under two years
  • Aged 65 years and older
  • Suffering from chronic disease such as asthma, diabetes, heart, or lung disease
  • Pregnant
  • Morbidly obese
  • Nursing home or chronic-care facility residents

Even though this year’s vaccine does not directly protect against this particular H3N2 strain, CDC Director Tom Frieden, MD, said during a news briefing, it is still recommended that people get their annual flu shot.

The vaccine will protect against several active strains of flu, and could even provide some protection against mutated flu viruses, he said. “If we have a severe season, getting a vaccine that provides even partial protection may be more important than ever,” he added.

According to CDC surveillance data, seasonal flu activity has increased slightly but is still within regular parameters. Only Louisiana and Puerto Rico were experiencing high levels of influenza-like illness, as of Nov. 22.