For the first time, researchers report drug resistance in type B influenza virus, which causes about 30 percent of flu cases in the United States. Furthermore, the researchers say that unlike a previously noted drug-resistant type A strain, this strain may jump from person to person.
"We've found a very clear case of resistance in the presence of antiviral drugs," says Yoshihiro Kawaoka of the University of Tokyo and the University of Wisconsin–Madison.
Kawaoka's team studied flu in children infected during a 2004–2005 type B outbreak in Japan. They collected viruses before and after the children had been treated with zanamivir or oseltamivir, two drugs more commonly prescribed in Japan than elsewhere.