Acute infectious diarrhea: Common germs and routes of infection

Photo of man feeling unwell (PantherMedia / Wavebreakmedia)

In Germany, infectious diarrhea is most commonly caused by the norovirus. Infants and young children often have rotavirus infections as well. Viral infections are usually quite intense but short. Bacterial infectious diarrhea is also widespread in adults.

Infections with the highly contagious norovirus or rotavirus typically start with sudden and severe symptoms such as diarrhea or vomiting. These symptoms usually go away after a few days. Since 2013, the German Standing Committee on Vaccination (STIKO) has recommended that infants be vaccinated against the rotavirus.

Bacterial infectious diarrhea is most often caused by eating contaminated or spoiled food. Like viruses, bacteria such as Campylobacter or Salmonella can also be transmitted through direct contact with infected people or by touching contaminated objects.


Rotaviruses most commonly infect infants and young children between the ages of 6 and 24 months. A child's first rotavirus infection usually causes severe symptoms, whereas later infections are milder. If children have several rotavirus infections, they become immune to the virus, but the immunity does not last for the rest of their lives. Adults under the age of 60 have fewer infections than children, and usually have milder symptoms as well. Common sources of infection include long-distance travel and their own children.

Rotavirus infections are more common in older people and those with weakened immune systems. Their symptoms may be so severe that hospital treatment is needed.

It usually takes about one to three days for rotavirus symptoms to start. They then last about two to six days. Common symptoms include:

  • Sudden watery diarrhea (often with mucus in it)
  • Vomiting
  • Stomach ache
  • Fever
  • Feeling weak and dazed from loss of fluids
  • Breathing difficulties in half of all affected people


In Germany, norovirus infections are especially common in children under the age of five years and adults over the age of 70. Infection is possible at any time of the year, but most often occurs between October and March.

It can take anywhere from six hours to two days for a norovirus infection to start causing symptoms. The symptoms often start quite suddenly, and include:

  • Severe diarrhea
  • Severe projectile vomiting
  • Stomach ache
  • Sometimes nausea, headaches, muscle ache, exhaustion and a mild fever

The symptoms usually only last about 12 to 48 hours. If too much fluid is lost due to severe diarrhea and vomiting, people may feel dizzy, drowsy and faint too.

How do the viruses spread?

Noroviruses and rotaviruses are most often transmitted through direct contact with infected people, touching contaminated objects and, less often, eating contaminated food. The viruses, which are found in stool and vomit, can be transferred through direct contact. Noroviruses can also be spread to others through tiny droplets in the air when someone vomits.

Viruses may survive on toilets, door handles or clothing, where they remain infectious for several days. Indirect infection is possible if you touch a contaminated object with your hand, and then touch your mouth with your hand. So if you want to protect yourself and others from infection, it's especially important to wash your hands regularly and thoroughly.

If viruses enter food through droplets, contaminated objects or poor hand hygiene, eating that food can lead to an infection. But, unlike bacteria, the viruses don't multiply when on food.

Rotaviruses are still found in stool about eight days after the symptoms have died down. Noroviruses can still be detected up to 14 days later. These viruses are only rarely found in stool for longer than that, apart from in people with weakened immune systems: Noroviruses may still be found in their stool several months or even years after initial infection.

What vaccines are available?

Since August 2013, the German Standing Committee on Vaccination (STIKO) has recommended rotavirus vaccinations for infants under the age of six months. Two vaccines are available: Both are used as an oral vaccine that is swallowed, instead of an injection.

Depending on the vaccine used, two or three doses of the vaccine are given, with an interval of at least four weeks between the doses. The series of vaccinations should be started at the age of six to twelve weeks and then finished by the time the infant is 24 or 32 weeks old at the latest. The exact ages will depend on which vaccine is used. Experts estimate that a rotavirus vaccination will offer protection for about two years.

Current studies show that, within a period of up to two years,

  • about 40 out of 1,000 children who are not vaccinated have a severe rotavirus infection, compared to only
  • about 6 out of 1,000 children who are vaccinated.

Vaccination is not recommended for older children or adults. Side effects of rotavirus vaccinations include mild diarrhea, vomiting or a fever. But they usually pass quickly.

There is no norovirus vaccine.

What kinds of bacteria cause diarrhea?

Many different types of bacteria can cause infectious diarrhea. Most of them aren't a problem in Germany due to good general hygiene. In Germany, bacterial infectious diarrhea is most commonly caused by Campylobacter or Salmonella. In rare cases, diarrhea is caused by certain strains of Escherichia coli, such as EHEC (enterohemorrhagic Escherichia coli) or Yersinia.

Bacteria often multiply in food, and can't usually be detected based on a certain smell or taste. All types of bacteria can be spread from one person to another through direct contact or by touching contaminated objects as well.


The most common form of bacterial diarrhea is caused by Campylobacter. These bacteria can live in raw meat - usually poultry, but also ground beef, for example. They are also sometimes found in raw milk (unpasteurized) or dairy products. It is also possible to pick up the bacteria from the stool of infected pets or contaminated waters.

In order to prevent Campylobacter infections, it is important to keep a clean and hygienic kitchen. Excess water from defrosting poultry or other types of meat should be disposed of immediately. It is important to cook meat well in order to make sure that any bacteria have been killed. Cutting boards used to prepare raw meat should be carefully cleaned each time they are used, and kitchen towels should be washed at a temperature of at least 60 degrees Centigrade.

Symptoms typically start two to five days after infection. They include

  • fever, headache and muscle ache, followed by
  • severe stomach ache and abdominal cramps,
  • nausea and diarrhea.

In very rare cases, Campylobacter infections can cause complications like rheumatic joint inflammations or paralysis.

These problems usually last up to one week. But many infections run their course undetected. It can take between two to four weeks until the stool no longer contains bacteria. This may take even longer in people who have weakened immune systems.


Salmonella bacteria are most often transmitted through raw foods. Eggs, egg-based foods like mayonnaise or dessert mousse, raw meat, and undercooked meat products are the most common sources of Salmonella infections. These bacteria can also get into food as a result of poor hygiene in the kitchen, for example through the use of contaminated cutting boards. Salmonella symptoms start within six hours to three days after infection, and last several days. They include the following:

  • Sudden diarrhea
  • Headache and stomach ache
  • Sometimes vomiting and a slight fever too

Very rarely, and mostly in people who have weakened immune systems, Salmonella infections can also cause blood poisoning (septicemia).

People who have been infected with Salmonella are often still contagious up to one month after the symptoms have disappeared. Young children and older people may still have bacteria in their stool for several weeks or months.


EHEC (enterohemorrhagic Escherichia coli) can be spread through raw foods such as meat products that have not been cooked enough. The bacteria can also live on unwashed vegetables and in unpasteurized fruit juices or unpasteurized milk. The stool of infected cattle and other animals that chew the cud (e.g. goats, sheep) is also contagious. EHEC bacteria are sometimes found in bodies of water too.

EHEC infections are most common in children and infants. They can sometimes pass without causing any symptoms, but in most cases the following symptoms arise three to ten days after infection:

  • Watery diarrhea
  • Nausea, vomiting and stomach ache
  • Sometimes fever as well

Very rarely, hemolytic uremic syndrome (HUS) may develop too. HUS is a blood clotting disorder that can damage the kidneys and become life-threatening.

The bacteria may still be present in stool for several weeks after the symptoms have cleared up. In very rare cases, EHEC can cause bloody diarrhea accompanied by stomach cramps.


Although rare, Yersinia can be spread through contaminated meat, milk or water. Pork that has not been thoroughly cooked is one main source of infection. Signs of yersiniosis include stomach ache, diarrhea and a moderate fever. The symptoms usually last 5 to 14 days.