Health officials say they aren't too worried, for several reasons. First, it's early in the flu season, and it's not clear this strain will dominate through the next several months. Second, not many people take antiviral medications for the flu.
Third, the flu vaccine - the primary weapon against flu - seems well matched against the circulating bugs.
But doctors need to take it seriously, said William Schaffner, a Vanderbilt University infectious diseases expert.
"Each influenza seasons provides a bit of a surprise and we got our (surprise) a little early this year," he added.
The flu causes 200,000 hospitalizations and 36,000 deaths annually, according to official estimates. The elderly, young children and people with chronic illnesses are considered at greatest risk.
For the public, the best course of action is vaccination, health officials said. Only about 30 percent of U.S. adults had gotten a flu vaccination this flu season, according to an online survey conducted by the RAND Corporation in November. A flu shot is recommended for those 50 and older, children from 6 months to 18 years, pregnant women, nursing home patients and those with certain medical conditions or who care for people with those conditions.
For people who get the flu, the two most commonly used antivirals are Tamiflu, a pill also known as oseltamivir, and Relenza, an inhaled drug also called zanamivir. The drugs are most effective if taken within two days of getting sick but most people don't see a doctor that quickly.
Early tests indicate that 49 of 50 samples of the main flu virus circulating this year
- H1N1 - were resistant to Tamiflu. The samples came mainly from Hawaii, Texas and ten other states. Widespread flu has not yet been reported in most of the country.
"It could fizzle out," or H1N1 could become the dominant strain, Gerberding said.
