Caliciviruses (Norovirus) in the hospital environment

Abstract

Norovirus outbreaks are an increasing public health problem in hospitals. Of all outbreaks of gastroenteritis in hospitals, 35–63% are attributed to Noroviruses. Epidemic curves of outbreaks exhibit primary, secondary, and sometimes tertiary cases. Person-to-person transmission by direct contact, through aerosol or contaminated surfaces, or through food handled by infected food-handlers, are the main transmission routes of Norovirus infection. Most frequently affected are the medical, pediatric, orthopedic, and geriatric wards, including psychogeriatric hospitals and other health-care facilities for the elderly. The risk of being affected by an outbreak is significantly greater on wards that have reported outbreaks previously. The attack rate is around 50% for patients (≈ 25% for the staff) and the infective dose is as small as 1–10 virus particles. The very short incubation time (12–48 h) demands rapid intervention. Although Norovirus illness is short-lived and usually self-limiting, the infections can lead to ward and sometimes hospital closures, with a major impact on patient care and, potentially, hospital finances. The recent development of novel molecular methods for detecting and differentiating Norovirus has allowed diagnosis of the virus with increased sensitivity and specificity. Genotyping of strains is an important tool for uncovering transmission routes and the appearance of epidemic strains. When an outbreak is suspected, infection control measures must be implemented immediately to limit a Norovirus outbreak. Furthermore, an outbreak surveillance system must be maintained for monitoring local and national trends of Norovirus outbreaks.