Web Zap*Germs Archive

May 19, 2005

Likely Increase of Norovirus Intestinal Infections

Despite a large growth of knowledge recently about noroviruses, we really don't know how to control them and it's likely their incidence will increase in the future. So writes Marc-Alain Widdowson of the CDC, lead author of an interesting commentary article in the current issue of Emerging Infectious Diseases. First discovered in 1929 as "winter vomiting disease," noroviruses are now recognized as a leading cause of nonbacterial intestinal infections (or "acute gastroenteritis") that cause cramps, vomiting and diarrhea.

A number of factors are likely to bring about more cases of norovirus in coming years, say the Widdowson team. While better refrigeration and monitoring of public food supplies are reducing the incidence of bacteria-caused gastroenteritis (like Salmonella and E. coli), unlike bacteria, noroviruses are resistant to cholorination in water, refrigeration and freezing. It also takes a lower dose of the virus than bacteria to make you sick.

There are also several lifestyle changes underway that are likely to help noroviruses spread more easily:
  • more elderly people live in communal settings, with the number of beds in nursing homes increasing
  • we eat more processed and pre-prepared foods today, both in restaurants and from grocery stores; this increases the likelihood of our food having been handled by infected workers
  • we also eat more foods like fresh fruits and vegetables that are likely to have been exposed to noroviruses -- as more imported fresh foods are being imported from countries where crops are irrigated with sewage-contaminated water
  • more people travel than ever before, increasing norovirus infection risk through exposure to hotels, airplanes, and cruise ships.

  • So, what's to be done? That's essentially what the authors are asking the medical community. More research is needed, they say, with better ways of tracking the spread of diseases and better tests to identify them as the culprits.

    Second, "we do not know how to stop norovirus transmissions. Foods can be contaminated...either at the source or at the point of service by infected food handlers. Noroviruses can spread by water, direct person-to-person contact, or airborne droplets of vomitus, and they can persist in the environment as a source of continuing infection despite efforts at disinfection."

    Only by developing a full strategy to prevent, detect and kill noroviruses, say Widdowson et al, can the likely rise of norovirus infections be countered.

    Sounds expensive, but worth doing.


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