The Claim: Hand Sanitizer Stops Norovirus Spread As public health officials struggle to contain a series of viral outbreaks this winter, many people are reaching for bottles of hand sanitizer. Studies show that alcohol-based sanitizers, particularly those with 60 percent ethanol or more, can reduce microbial counts on contaminated hands and reduce the spread of some strains of the flu. But against norovirus, the severe gastrointestinal illness gripping many parts of the country, they may be useless. Some viruses, like influenza, are coated in lipids, "envelopes" that alcohol can rupture. But non-enveloped viruses, like norovirus, are generally not affected. Bleach is effective against norovirus, and can be used to decontaminate countertops and surfaces. And for people, the best strategy may be washing hands with plain old soap and water. In 2011, the Centers for Disease Control and Prevention studied 91 long-term care facilities. During the winter of 2006-07, they identified 73 outbreaks, 29 of which were confirmed to be norovirus. The facilities where staff members used alcohol-based sanitizers, were six times more likely to have an outbreak of norovirus than the facilities where the staff preferred using soap and water. The C.D.C. says that as a means of preventing norovirus infection, alcohol-based sanitizers can be used "in addition" to hand washing, never as a substitute. Hand sanitizers can reduce the spread of some viruses, like the flu. But against norovirus they are largely ineffective; better to use soap and water.