New research has demonstrated increasing resistance to antivirals in certain influenza strains signaling the need for continued detailed studies of influenza virus strains, and the development of new medications. While resistance to either adamantanes or neurominidase inhibitors (such as oseltamivir or zanamivir), the two classes of antivirals, has been well documented in the past years, new research has shown that some viruses are resistant to both classes of drugs. Further, researchers demonstrated that virus strains with resistance to one antiviral medication can develop this dual resistance. Strains with dual resistance are rare, but researchers have observed an increase in the number of tested viruses with dual resistance, from .06% in 2007-2008, to 1.5% in 2008-2009, to 28% in 2009-2010. In addition, a study of oseltamivir-resistant pandemic H1N1 virus was the first to determine that the virus could be transferred from person to person. This study examined an outbreak of the virus among immunocompromised patients in a hematology unit. Both studies are published in the January 2011 issue of the Journal of Infectious Diseases.