Office of Communicable Diseases

Norovirus Infection

High Circulating Levels of Norovirus in RI

Background : High levels of Norovirus are circulating in Rhode Island. To date, the Rhode Island Department of Health (HEALTH) has responded to seven institutional outbreaks, six of them confirmed as Norovirus gastroenteritis. Indirect indicators through syndromic surveillance indicate increased GI illness community wide. Other states in the northeast are reporting similar increases.

Agent : Norwalk-like viruses, now classified under the genus Norovirus, cause an estimated 23 million infections, 50,000 hospitalizations, and 300 deaths among Americans each year and are the leading cause of gastroenteritis outbreaks. At least 23 types of noroviruses can infect humans. Although infection from noroviruses can occur anytime of year, there is a seasonal peak that begins in November and continues throughout the winter months.

Public Health Implications : Transmission is oro-fecal and from contaminated environmental sources. The virus requires a very low inoculating dose to transmit infection, and the incubation is short (1 to 2 days). Several strains exist, so exposure to one strain will not protect against exposures to other strains. Immunity is short lived, so it is possible to be reinfected with the same strain. The virus is environmentally stable and can remain infective on environmental surfaces for several days, facilitating transmission through fomites, food and water. Finally, people may continue to shed virus for 24 to 72 hours and sometimes as long as two weeks after symptoms have ceased. All of these factors contribute to rapid transmission and wide dissemination especially in crowded environments, and associated with ill food handlers and health care workers.

Report outbreaks to HEALTH: 222-2577 (after hours: 272-5952).

Clinical Features : The symptoms of Norovirus illness usually include sudden onset of nausea, vomiting, diarrhea, and abdominal cramping. Sometimes people additionally have a low-grade fever, chills, headache, muscle aches, and a general sense of tiredness. The illness often begins suddenly, and the infected person may feel very sick. The illness is usually brief, with symptoms lasting only about 1 or 2 days. Norovirus disease is usually not serious, although people may feel very sick and vomit many times a day. When people are ill with vomiting and diarrhea, they should be assured of appropriate access to fluids to prevent dehydration. Dehydration is the most serious health effect that can result from Norovirus infection. By drinking oral rehydration fluids (ORF), juice, or water, people can reduce their chance of becoming dehydrated.

Infection Control Procedures :

• Wash hands thoroughly after using the restroom or changing diapers or assisting someone to use the restroom or after assisting someone who is ill, and before preparing or eating food.
• Exclude ill people from preparing food or providing medical or childcare for at least 24 hours after resolution of symptoms. Also exclude ill children from daycare and school.
• Food handlers should stay home, if sick, for at least 24 hours after symptoms have resolved.
• No bare hand contact with ready-to-eat foods in commercial food establishments.
• Health care workers should practice strict infection control measures in caring for infected patients.
• Facilities need to follow strict environmental sanitization and other situation specific outbreak control measures recommended.

For more information : Call HEALTH, Office of Communicable Diseases at: 222-2577 from 8:30 a.m. to 4:30 p.m. Monday-Friday, or visit the CDC Norovirus web page at:

http://www.cdc.gov/ncidod/dvrd/revb/gastro/norovirus.htm