How long does it take a stomach bug to spread through a busy building - like a hospital or office block - from just a single contamination of an elevator button or light switch? Only a few hours, according to a new study presented at a meeting in the US this week that also found commonly used disinfectants can stop it.

Noroviruses, the most common cause of "stomach flu" or gastroenteritis, can spread rapidly and are responsible for numerous closures of schools, office buildings, nursing homes and other busy facilities. Contaminated surfaces, on which they can exist for days, are thought to be important in the spread of noroviruses; a common way to become infected is to touch a contaminated surface and then touch your mouth.

Virus spread through 40-60% of building and occupants in 2-4 hours

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The new study revealed that a virus can spread to up to 60% of people in large buildings via frequently touched objects within 2-4 hours.

For their study, the researchers dabbed samples of a tracer virus - used as a surrogate for human norovirus - onto one or two frequently touched surfaces and objects, such as a table top or door knob, in office conference rooms and a health care facility.

Within 2-4 hours, they found traces of the virus on 40-60% of the people and frequently touched objects in the building. The researchers took samples from up to 100 high-touch areas, including light switches, bed rails, countertops, push buttons, coffee pot handles, door knobs, table tops, computers and phones.

Charles Gerba, professor of Microbiology & Environmental Sciences at the University of Arizona, Tucson, presented the findings at the 54th Interscience Conference on Antimicrobial Agents and Chemotherapy (ICAAC) that is being held in Washington, DC, from September 5-9, 2014.

Prof. Gerba says the study also showed the solution to stopping the virus spreading is simple. He and his colleagues discovered this when they provided cleaning staff in the facilities with disinfectant wipes containing quaternary ammonium compounds (QUATS) and instructed them how to use them properly and to use them at least once a day to clean frequently touched objects and surfaces.

QUAT-based disinfectants reduced virus spread by 80-99%

"Using disinfecting wipes containing quaternary ammonium compounds (QUATS) registered by EPA [Environmental Protection Agency] as effective against viruses like norovirus and flu, along with hand hygiene, reduced virus spread by 80-99%," he says.

According to the US Centers for Disease Control and Prevention (CDC), each year, noroviruses cause an estimated 19-21 million illnesses and contribute to 56,000-71,000 hospitalizations and 570-800 deaths.

In their study, Prof. Gerba and colleagues used bacteriophage MS-2 as a surrogate for the human norovirus, as it has a similar shape and size and reacts to QUAT-based disinfectants in a similar way.

A QUAT-based disinfectant works against the virus because it carries a negative charge, and the disinfectant carries a positive charge. When the virus comes into contact with the QUATS, the charge distribution of the virus changes and leads to its destruction. QUATS have a similar effect on bacteria - resulting in destruction of their cell walls.

There are over 1,500 branded disinfectants in the US that use one or more of the 90 different EPA-registered QUAT-formulations for killing norovirus on solid surfaces. These are available as wipes, ready-for-use liquids, and in concentrate forms.

Prof. Gerba says their study shows viral contamination of frequently touched objects and surfaces can spread rapidly in buildings, and that a "simple intervention can greatly help to reduce exposure to viruses."

Meanwhile, at another study presentation, delegates at ICAAC 2014 also learned how superbug infection risk increases with length of hospital stay. Researchers at the Medical University of South Carolina found if a patient acquires a gram-negative infection in the hospital, the chances of it being multidrug-resistant goes up by 1% for each day of hospitalization.