Norovirus is a very contagious virus. Every year, food poisoning is reported in France because of this virus. Among the foods incriminated: shellfish, oysters, etc.
It’s often around the holidays that we hear about “norovirus”, particularly because it contaminates oysters. Norovirus causes brief symptoms in healthy people. They last on average 2-3 days sometimes more, up to 6 days, in the most fragile. Elderly people or those with chronic pathologies, or very young children should be particularly attentive to these symptoms, as they are more vulnerable to complications.
What is norovirus?
Norovirus is a virus that belongs to the Caliciviridae family. These viruses were previously known as Norwalk, Norwalk-like, or Calicivirus viruses. These viruses – very resistant – constitute the main causes of acute gastroenteritis. It is also the infectious agent most frequently responsible for epidemics of gastroenteritis which occur in communities (nurseries, hospitals, schools, retirement homes, cruise ships, etc.). The majority of foodborne norovirus outbreaks are linked to the consumption of shellfish contaminated during accidental spills of wastewater or network distribution water following network malfunctions.
What are the symptoms of norovirus poisoning?
Norovirus infection can lead to gastro symptoms-enteritis like:
- The sudden onset of vomiting and nausea
- Diarrhea
- Abdominal cramps
- Moderate fever (low fever reported in less than 50% cases)
- Sometimes headaches
- Sometimes aches
- Sometimes chills
What are the risks of complications?
In immunocompromised people or young children, norovirus poisoning can lead to complications such as:
- Dehydration with (significant) weight loss.
- A disturbance of electrolytes (hypokalemia).
- Kidney failure which can lead to death.
Is norovirus contagious?
Yes, norovirus is a very contagious virus. The peak excretion of the virus in the stools varies from 3 to 10 days depending on the individual. Indeed, “excretion in the stools can be high (up to 1011 particles/g of stool) and prolonged over time (two to three weeks after symptoms disappear). Asymptomatic people (1/3 of poisoned people are asymptomatic) can also shed the virus in significant quantities. Very high quantities of viral particles are therefore present in discharges during winter epidemics.“, reports ANSES.
What is the incubation time for norovirus?
A norovirus infection can cause symptoms of gastroenteritis, the incubation period of which can range from 10 to 50 hours (up to approximately 2 days), according to ANSES.
Transmission by the fecal-oral route (from stool to the mouth) is the most important. A person can become infected in several ways:
► By having direct contact with a sick person (taking care of a sick person, sharing food, drinks or utensils with a sick person)
► Touching surfaces or objects contaminated with norovirus and then putting your fingers in your mouth (contaminated surfaces, handles or faucets in the washroom)
► Eating food or drinking liquids contaminated with norovirus (a sick food handler contaminating food or drinks);
Treatment: what to do in case of norovirus poisoning?
Antibiotics are ineffective.
No antiviral treatment currently exists to treat norovirus infections or a vaccine to prevent infection. Antibiotics are ineffective. According to the PACA Regional Health Agency, the only treatment consists of the prescription of supportive care such as oral rehydration (water with a little salt and sugar, oral rehydration solution found in pharmacies, juice, clear soup or more consistent depending on tolerance), sometimes antiemetics and oral or isotonic IV fluids (electrolyte powder to quickly rehydrate the body). Antidiarrheals (e.g. loperamide) can be given to adults but not to children under 18 who have acute diarrhea and to any patient who has recently taken antibiotics, has bloody diarrhea, or has diarrhea with fever.
What prevention to avoid norovirus poisoning?
Noroviruses are resistant to conventional food preservation methods (refrigeration and freezing) as well as temperature (30 min at 60°C) and pH variations. Commonly recommended precautions to prevent bacterial growth have no effect on viral contamination. However, hygiene rules must be respected in the event of a sick person in the household:
► Avoid consuming shellfish if they do not come from an authorized and controlled farming area or after prolonged cooking
► Insist on careful hand washing when leaving the toilet, before preparing and eating meals.
► Thoroughly clean and then disinfect soiled surfaces immediately after an episode of illness (vomited matter, diarrheal stools) using bleach
► Immediately remove and clean, in hot water with detergent, clothing, sheets or other fabrics that may have been contaminated after an episode of illness
► Dispose of vomited matter or diarrheal stools in the toilet and ensure that the surrounding area is always clean.
► People infected with norovirus should not handle food.
