It starts suddenly: When a stomach bug strikes out of nowhere, noroviruses are often the culprits. Here, we answer the most important questions about this unpleasant virus.
How is norovirus transmitted?
Whether in care homes, on holiday camps or cruise ships, when one person is infected, it often spreads quickly to many others.
"It's very easy to get infected because the unique thing about norovirus is that even a small dose - 10 to 100 individual viruses - is enough," says gastroenterologist and internal medicine specialist Professor Birgit Terjung.
The virus can stick to surfaces - such as tables, door handles or even food - and be transmitted by contact. "However, it is mainly spread through stool and vomit," explains Terjung. When someone vomits, the virus can float in fine aerosols through the air, leading to infection via droplet transmission.
How long does it take for symptoms to appear?
From "the first viruses are in the body" to "I don't feel well": The incubation period for norovirus is relatively short, according to Terjung. Symptoms can start as soon as six hours after contact with the virus, but they may also take up to 50 hours to appear. Generally things move much faster than with other viruses, and especially compared to bacteria.
Those who have experienced norovirus know: "The symptoms come on almost explosively," says Terjung. "You have to vomit very frequently and experience severe diarrhoea. This is accompanied by a strong feeling of illness: fatigue, headaches, often fever and severe abdominal pain." After 48 hours, symptoms usually improve, and the discomfort subsides.
Someone in the family or shared flat is infected: What hygiene rules should be followed to prevent further infections?
If someone is suffering from diarrhoea or vomiting, they will spend a lot of time in the bathroom. Whether in a shared flat or family home, hygiene is crucial to prevent others from getting infected.
"If someone vomits into the toilet and another person uses it afterwards without knowing, it can easily lead to infection," says Terjung.
Ideally, the infected person should clean the toilet themselves after use. "If someone else has to clean it, they should ideally wear a mask," advises Terjung. This helps protect against infectious aerosols.
"Wear gloves and wash your hands thoroughly with soap and water afterwards, including your arms. If available, use disinfectant as well."
It's best to have a disinfectant in the cleaning cupboard that works against viruses. For cleaning, wearing an apron is also recommended to prevent viruses from sticking to everyday clothing.
I'm infected. What should I do now?
A typical feature of norovirus infection is that the body loses a lot of fluids. "The danger is that if you are ill for several days, you can become dehydrated because you lose a lot of fluids through vomiting and especially through liquid diarrhoea," says Birgit Terjung.
As soon as possible, you should start replenishing fluids by drinking. However, to avoid overwhelming the body, don't drink half a litre at once.
Instead, start with small sips. "At the beginning, the stomach is still very irritated. This means that whenever something enters, no matter what it is, the stomach reacts with cramps, and you feel like vomiting again."
What are the warning signs of dangerous fluid loss?
Young children and older adults are particularly at risk of severe dehydration. In some cases, they may need to be hospitalized to receive fluids via an intravenous drip.
Signs of critical dehydration include: "If the tongue is completely dry, rough and deeply cracked when you look at it. Patients themselves often say: My mouth is so dry," explains Terjung.
Other warning signs include severe headaches and drowsiness. The skin fold test can also provide a clue: "If you pinch the skin on the forearm and it stays in a fold when you let go, that's a typical sign of severe dehydration," says the doctor.
What should I drink - and how should I start eating again?
The best options are water and teas, but other drinks are not off-limits. "I wouldn't recommend cloudy apple juice because it has a slight laxative effect," says Birgit Terjung. "A little cola, on the other hand, is fine - often people crave something sweet."
However, relying solely on cola during a norovirus infection is not advisable due to its high sugar content. Since a stomach bug flushes many minerals out of the body, it's important to replenish them.
This can be done with electrolyte solutions from the pharmacy or a WHO-recommended solution for diarrhoeal illnesses. To make it, mix:
Clear soups are another good way to restore essential salts. As for food, you can slowly reintroduce it.
"It should be something that doesn't sit heavily in the stomach - porridge, crackers or toast. It shouldn't be too fatty, as that can slow down the stomach," she advises.
It's over. When is someone no longer contagious?
If someone has been free of fever, diarrhoea and vomiting for 48 hours, they are generally no longer contagious, according to Birgit Terjung. However, thorough hygiene around the toilet should still be maintained. "It's possible to shed the virus in stool for up to two weeks," she says.
This is especially true for immunosuppressed individuals, such as those undergoing chemotherapy, who may continue to shed the virus for longer.