Norovirus, often inaccurately called the “stomach flu” or “winter vomiting bug,” is a highly contagious virus that causes acute gastroenteritis, which is the inflammation of the stomach and intestines. It is the most common cause of gastroenteritis outbreaks worldwide and affects people of all ages. This pathogen spreads rapidly, especially in crowded, closed environments like cruise ships, nursing homes, and schools.
Symptoms and Illness Duration
Symptoms typically begin suddenly, often within 12 to 48 hours of exposure. Common indicators include nausea, vomiting, watery diarrhea, and stomach cramping. Many people also experience general symptoms like a low-grade fever, headache, and muscle aches.
The illness is intense but short-lived, with most people recovering completely within one to three days. While symptoms are severe, the condition is usually self-limiting. The rapid fluid loss from vomiting and diarrhea can quickly lead to dehydration, which is the main concern, especially for vulnerable populations. Even after symptoms resolve, a person can continue to shed the virus in their stool for several weeks, meaning they remain potentially contagious.
Transmission Routes and Contagiousness
Norovirus is highly contagious, requiring an infectious dose as low as 18 to 1,000 viral particles. This low threshold facilitates its rapid spread through multiple routes. The primary method of transmission is the fecal-oral route, where viral particles from an infected person’s stool or vomit are accidentally ingested.
Contamination often occurs indirectly through contact with contaminated surfaces (fomites) or by consuming food or water handled by an infected person. The virus also spreads via aerosolized particles created during forceful vomiting, which can contaminate the air and settle on nearby surfaces, leading to further transmission. The virus is environmentally stable, hardy, and resistant to many common disinfectants, including alcohol-based hand sanitizers.
Essential Management and Hydration
Since Norovirus is a viral infection, antibiotics are ineffective, and there is no specific cure. Management focuses on supportive care, with the prevention and treatment of dehydration as the main objective. The constant fluid loss from vomiting and watery diarrhea rapidly depletes the body of water and essential electrolytes.
Oral Rehydration Solutions (ORS) are the preferred fluid, as they contain the correct balance of sugars and salts to help the body absorb water efficiently. Small, frequent sips of fluid are better tolerated than drinking large amounts at once, especially if vomiting is persistent. Medications like over-the-counter anti-diarrheals should be avoided unless directed by a healthcare provider, as they can sometimes prolong the illness. Medical attention is necessary if signs of severe dehydration develop, particularly in young children, older adults, or those with underlying health conditions.
Signs of Severe Dehydration
Warning signs include:
- Lethargy
- Dizziness
- Dry mouth
- Significantly decreased urine output, such as no urination for eight or more hours
If a person is unable to keep any fluids down due to persistent vomiting, intravenous (IV) fluids may be required to restore hydration and electrolyte balance. Once vomiting subsides, bland foods like bananas, rice, or plain toast can be gradually reintroduced.
Practical Steps for Prevention
Stopping the spread of Norovirus relies on strict hygiene and proper environmental disinfection. Handwashing remains the most effective preventative measure, as the virus is not easily killed by alcohol. Hands must be washed thoroughly with soap and water for at least 20 seconds, particularly after using the restroom, changing diapers, and before preparing or eating food.
Cleaning protocols must account for the virus’s resistance to standard cleaners. Surfaces contaminated with vomit or feces require a chlorine bleach solution with a concentration of 1,000 to 5,000 parts per million (ppm), which is equivalent to five to twenty-five tablespoons of household bleach per gallon of water. This strong solution must be left on the surface for at least five minutes before being wiped clean.
Contaminated clothing and linens must be handled carefully to avoid shaking viral particles into the air. They should be washed immediately using detergent and the hottest water setting the fabric can tolerate, followed by a machine dry on the highest heat setting. Individuals who are ill should avoid preparing food or caring for others for at least 48 hours after their symptoms have completely resolved.