A new flu strain that is spreading across the U.S. does not respond to the medication Tamiflu, according to the Centers for Disease Control and Prevention.
The CDC warned that this year’s most commonly noted flu bug, found in 12 states so far, is the one that is resistant to Tamiflu.
There are three different strains of flu that can affect humans: the A H3N2 strain, a type B strain and the resistant A H1N1 strain.
Still, Tamiflu is one of the most popular anti-flu drugs on the market, possibly because it can be administered to children in pill form.
But some have raised concerns about the medication’s safety. In 2005 and 2006, a number of cases – mainly out of Japan – reported that children and young people were experiencing mental health side effects after taking the drug.
This caused manufacturer Roche to add a warning to its label stating that "people with the flu, particularly children, may be at increased risk of self-injury and confusion shortly after taking Tamiflu and should be closely monitored for signs of unusual behavior."