Norovirus - Information for Clinicians
Type of infection
Noroviruses are a diverse group of caliciviruses that fall into 3 genogroups, GI, GII, and GIV. Genogroups GI and GII are the predominant circulating genogroups; genogroup GIV is rare. Previously called Norwalk virus.
Sources of infection
- Norovirus is the most common cause of gastrointestinal illness in the US, causing 19-21 million cases per year.
- Most common cause of foodborne outbreaks.
- Very low infectious dose, prolonged shedding, and resistance to common disinfectants add to infectivity.
- Spread can occur from food contaminated by ill people during harvesting activities, food preparation, or transportation. Contamination of surfaces with stool and vomitus contributes.
- Causes outbreaks in hospitals, schools, nursing homes, and cruise ships.
Usual symptoms
- Illness usually starts 10-70 hours after exposure.
- Sudden onset of vomiting and diarrhea, abdominal pain or cramps, and low-grade fever.
Duration of illness
- Typically 1-3 days but can last up to 7 days.
- Longer illness in young children, the immunocompromised, and those with underlying illnesses.
Treatment
- Fluid replacement and correction of electrolyte abnormalities. Antiemetics may be helpful in adults and teenagers. Antimotility agents may be useful for older children and adults.
- Antibiotics do not help and may make diarrhea worse.
Complications
- Dehydration is the major complication.
Comments
- Norovirus is resistant to many disinfectants, including alcohol-based hand hygiene.
- Wash hands carefully with soap and water.
- Clean contaminated surfaces with disinfectant or bleach solution (5-25 tablespoons of household bleach per gallon of water) or an EPA-registered disinfectant.
- Spread in households and school is common - instruct patients in ways to decrease transmission.