Norovirus disinfection: How much is enough?

A variety of institutions and governments have developed "commonsense-based" disinfection guidelines to control norovirus contamination, but now, for the first time, a Dutch team has come up with science-based guidelines. The research is published in the November 2012 issue of the journal Applied and Environmental Microbiology.

is the most common cause of , according to the (). This fecal-orally transmitted virus is notorious for spreading like wildfire in schools, on ocean cruises, and where-ever one infected person may be involved in the feeding of hundreds more, leaving victims tossing their cookies for as long as several days. Norovirus is especially problematic when it strikes hospitals, as both staff and patients are laid low.

In the study the researchers first determined how low the concentration of virions needed to go for transmission to become unlikely. They then tested different methods of cleaning hard surfaces, by using water, soap, or chlorine bleach solutions to determine the best method, or combination of methods for achieving a sufficiently low concentration to prevent from hard surfaces, such as your kitchen counters.

The researchers prescribe a two-step process: wipe with a wet cloth, and then disinfect with chlorine. Their prescription is directed at hospitals, schools, restaurants, and other food-handling establishments. In most cases, a 250 ppm solution of chlorine is sufficient, but for high levels of contamination, they recommend 1,000 ppm, says principal investigator Erwin Duizer, of the National Institute for Public Health and the Environment, Bilthoven, the Netherlands.

To achieve 1,000 ppm, one Suma Tab D4 tablet must be dissolved in 1.5 liters of water (about a quart and a half). Household bleach, says Duizer, is an average about 5 percent chlorine when new (concentration declines with age), or 50,000 PPM, and thus, can be diluted 50-fold to achieve the 1,000 ppm.

Norovirus is apparently no more resistant to cleaning and disinfection than other pathogens, says Duizer. The virus' efficiency in causing outbreaks "is more likely due to their extremely low infectious dose," resulting in the requirement of a very low level of residual contamination in order to prevent further transmission. "Fortunately, reducing the level of residual contamination to that low level is not that difficult and can be achieved without extreme measures," says Duizer.

"The current guideline for norovirus outbreaks in the Netherlands is quite stringent in some aspects," says Duizer. "During recent years I have heard many complaints from people in the field that 'it just can't be done.'" The new guidelines will be more practical, and thus more effective, he says.

More information: E. Tuladhar, W.C. Hazeleger, M. Koopmans, M.H. Zwietering, R.R. Beumer, and E. Deuzer, 2012. Residual viral and bacterial contamination of surfaces after cleaning and disinfection. Appl. Environ. Microbiol. 78:7769-7775.

add to favorites email to friend print save as pdf

Related Stories

NBA players not immune to serious illness from norovirus

Oct 31, 2011

A new study describes a 2010 outbreak involving several NBA teams, the first known report of a norovirus outbreak in a professional sports association. Published in Clinical Infectious Diseases and available online, the st ...

Deaths from gastroenteritis doubles

Mar 14, 2012

The number of people who died from gastroenteritis (inflammation of the stomach and intestines that causes vomiting and diarrhea) more than doubled from 1999 to 2007. The findings of this study will be presented today at ...

Food-safety expert warns, beware of Norovirus

Mar 01, 2012

The leading cause of foodborne disease is wreaking havoc this winter, according to a food-safety expert in Penn State's College of Agricultural Sciences, who says people should try to limit their exposure ...

Recommended for you

Overwhelmed west Africa ramps up Ebola response

4 hours ago

West Africa intensified its response to the deadly Ebola epidemic on Sunday, with Sierra Leone uncovering scores of dead bodies during a 72-hour shutdown and Liberia announcing hundreds of new hospital beds.

Sierra Leone reaches final day of Ebola lockdown

8 hours ago

Frustrated residents complained of food shortages in some neighborhoods of Sierra Leone's capital on Sunday as the country reached the third and final day of a sweeping, unprecedented lockdown designed to ...

Sierra Leone faces criticism over Ebola shutdown

Sep 20, 2014

Sierra Leone began the second day of a 72-hour nationwide shutdown aimed at containing the spread of the deadly Ebola virus on Saturday amid criticism that the action was a poorly planned publicity stunt.

Presence of peers ups health workers' hand hygiene

Sep 19, 2014

(HealthDay)—The presence of other health care workers improves hand hygiene adherence, according to a study published in the October issue of Infection Control and Hospital Epidemiology.

User comments