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Diarrhoea and Vomiting

By Bjarne Lühr Hansen PhD, MD and Philipp Skafte-Holm MD, Mentor Institute

Stomach flu with a virus is the most common cause of diarrhoea and vomiting. Infections with salmonella and campylobacter are however becoming more and more common. It is important to sufficiently heat-treat your food. You should drink plenty of fluids with salt and sugar.

When you have more than 10 thin stools a day, you have diarrhoea. Vomiting and diarrhoea are often caused by a gastrointestinal infection caused by virus (stomach flu) or more rare bacteria.

In connection with the vomiting there may be periodic stomach pains and slightly increased temperature. Typically, there are more people in the family or in your circle of acquaintances who are ill. The most cases disappear by themselves in the course of 36 hours.

Several different bacteria can cause a gastrointestinal infection. Two of the most common bacteria are salmonella and campylobacter. Most often, people are infected with other more rare bacteria in connection with travelling abroad.

Gastrointestinal infection with salmonella starts suddenly with nausea, watery and slimy stools, vomiting and periodic stomach pains. The temperature may rise to 39-40ºC and disappears again after a couple of days.

Gastrointestinal infection with campylobacter begins with queasiness for a couple of days. Hereafter, diarrhoea containing blood, light fever and very heavy stomach pains. Today, campylobacter is the most common cause of fever and bloody diarrhoea.

Salmonella and campylobacter are found in domestic animals, including poultry, pigs and calves. Meat that has not been sufficiently heat-treated can transmit salmonella and campylobacter to people. The risk is particularly high with eggs. Often, eggs is an ingredient in dishes that are not heat-treated like buttermilk koldskål, mayonnaise and vanilla cream. Salmonella and campylobacter can neither be seen, smelled or tasted in the food. Both bacteria are avoidable if you make sure to heat-treat your food sufficiently.

Your doctor can, by examining your stool, find out if it is a virus, salmonella or campylobacter that us causing the diarrhoea. Far most cases of salmonella or campylobacter disappears by themselves in the course of a couple of days.

Click here to assess the sick.


Gastrointestinal infection caused by virus is highly contagious. The illness infects from human to human by touch. Gastrointestinal infection caused by salmonella or campylobacter practically do not infect from human to human. Transmission of the disease occur when eating food that has not been sufficiently heat-treated.

When can I go to work?
When you are free of fever and the stool is becoming normal.


Far most cases of salmonella or campylobacter in the stool should not be treated with antibiotics but disappear in the course of a couple of days. In the case of prolonged diarrhoea, treatment with antibiotics may be an option. Possibly, the doctor will take some stool samples that are sent to closer examination.

What can you do?

If you have diarrhoea, vomiting and fever at the same time you lose a lot of fluid. This can lead to drowsiness and the urge to sleep the whole time. Therefore, it is important that you have plenty to drink and preferably drinks that contain salts and calories (for example tea with sugar, fizzy drinks or sweet lemonade. Avoid coarse and fibre rich food as long as the stool is thin. This only irritates the intestine to make the diarrhoea continue.

Contact the doctor tomorrow

If you for more than 48 hours vomit, have diarrhoea and fever or if there is blood in the stool.

Contact the doctor immediately

If you have persistent stomach pains. If you have become drowsy, cannot drink and prefer sleeping.