Several batches of oysters, sold in supermarkets in France, have been recalled due to contamination with norovirus, a highly contagious virus responsible for symptoms of gastroenteritis (diarrhea, vomiting, etc.). What is this virus? What are the risks of complications?
Many massive oyster recalls took place throughout France, warns the government site Drink reminder. A first recall of several batches of oysters was launched on December 30, 2022, the eve of New Year’s Eve, then on January 1 and 2, 2023. In question: norovirus infectiona virus very contagious which causes symptoms of gastroenteritis like the diarrhea and vomiting. These oysters are notably sold in supermarkets Leclerc, Super U, Intermarché, Carrefour… What is a norovirus? What symptoms in case of poisoning? What to do ? What are the risks of complications? How long are you contagious?
What is a norovirus?
Norovirus is a virus that belongs to the Caliciviridae family. These viruses were previously known as Norwalk, Norwalk-like or Calicivirus viruses. According to a document from ANSESthese viruses – very resistant – constitute the main causes of acute gastroenteritis (inflammation of the stomach and intestine) in humans of all age groups. It is also theinfectious agent most frequently responsible for gastroenteritis epidemics that occur in communities (nurseries, hospitals, schools, retirement homes, cruise ships…). The majority of foodborne norovirus outbreaks are linked to the consumption of contaminated shellfish during accidental spills of waste water or mains water following malfunctions in this network. Noroviruses can reproduce only if they infect a human.
Which oysters are contaminated with norovirus?
Recalls were launched on December 30, 2022, and January 1 and 2, 2023. They concern the following products:
- Vendée cupped oysters from Les 3 M (LOT 14/12 BASIN 4 CONDITIONED 17/20/21 DECEMBER BASIN 3 CONDITIONED 22/23 DECEMBER)
- BOUZIGUES OYSTERS
- CAMARGUE OYSTERS
- ORGANIC BOUZIGUES OYSTERS
- ST MARTIN OYSTERS
- SANCHEZ SIGNATURE OYSTERS
- SPECIAL MEDITERRANEAN FQC OYSTERS
- FQC BOUZIGUES OYSTERS
- BOUZIGUES OYSTERS: LA BELLE OCCITANE DE BOUZIGUES brand
- HOLLOW OYSTER UN°3 X 24 PIECES THAU: brand U
- BOUZIGUES OYSTERS GAEC MISTRAL
- FILTER SHELLFISH FROM THE ETANG DE THAU (Oysters-Mussels-Clams)
- BOUZIGUES OYSTERS SCA JOSI-MAR
- BOUZIGUES OYSTERS Nathalie and René Seashells
- BOUZIGUES OYSTERS Distrimers
>> See the precise list of batches concerned by the recalls.
What symptoms does norovirus cause?
A norovirus infection can lead to symptoms of acute gastroenteritis as :
- Sudden onset of vomiting and nausea
- Diarrhea
- abdominal cramps
- A moderate fever (low reported in less than 50% of cases)
- Sometimes headaches
- Sometimes aches
- Sometimes chills
The disease is rather brief in healthy people. These symptoms last on average 2-3 days (sometimes more, up to 6 days, in children and the elderly). It is right to consult your doctor quickly if you have these symptoms, mentioning the consumption of these oysters. Immunocompromised people (elderly people or people with chronic pathologies, or very young children) must be particularly attentive to these symptoms, which may suggest infection by a norovirus. The diagnosis is based on clinical suspicion in a patient with typical symptoms, especially during an outbreak and on PCR testing on a stool sample.
Asymptomatic people can also reject the virus.
What are the risks of complications?
In immunocompromised people or young children, norovirus poisoning can lead to complications such as:
- A dehydration with (significant) weight loss.
- A disturbance of electrolytes (hypokalaemia).
- A renal failure which may result in death.
Is norovirus contagious?
Yes, norovirus is a virus very contagious. The peak excretion of the virus in the stool varies 3 to 10 days depending on the individual. In effect, “fecal excretion may be high (up to 1011 particles/g feces) and prolonged over time (two to three weeks after symptoms disappear). Asymptomatic people (1/3 of intoxicated people are asymptomatic) can also reject the virus in large quantities. Very high amounts of viral particles are therefore present in releases 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 about 2 days)according to ANSES.
Transmission by fecal-oral route (stool to 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, drink or utensils with a sick person)
► By touching contaminated surfaces or objects with noroviruses and then putting your fingers in your mouth (contaminated washroom surfaces, handles or faucets)
► By eating food or drinking liquids contaminated with norovirus (a sick food handler who contaminates food or drink);
Treatment: what to do in case of norovirus poisoning?
Antibiotics are ineffective.
No antiviral treatment currently does not exist 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 pharmaciesjuice, clear soup or thicker according to tolerance), sometimes antiemetics and oral or isotonic IV fluids (electrolyte powder to quickly rehydrate the body). Of the antidiarrheals (loperamide for example) can be given to adults but not to children under 18 who have acute diarrhea and to any patient who has recently taken antibiotics, bloody diarrhea or diarrhea with fever.
What prevention to avoid norovirus poisoning?
Noroviruses are resistant to conventional food preservation methods (refrigeration and freezing) as well as to temperature (30 min at 60°C) and pH variations. Commonly recommended precautions to prevent bacterial growth have no effect on viral contamination. However, the rules of hygiene must be respected in the event of illness within the home:
► Insist on careful washing of hands when leaving the toilet, before preparing and eating meals.
► Carefully wash fruits and vegetables
► Thoroughly clean and then disinfect soiled surfaces immediately after an episode of illness (vomited matter, diarrheal stools) using bleach
► Immediately remove and clean, with hot water and detergent, any clothes, sheets or other fabrics that may have been contaminated after an episode of illness
► Dispose of vomited material or diarrheal stools in the toilet and ensure that the surrounding area is always clean.
► Persons infected with norovirus should not handle food.
► Avoid the consumption of shellfish, if they do not come from an authorized and controlled breeding area, or after prolonged cooking.
Sources: Conso.gouv reminder site / ANSES factsheet: norovirus / Questions and answers on norovirus (viral gastroenteritis) for patients and healthcare professionals, ARS PACA