Salmonellosis

Salmonellosis is a gastrointestinal disease caused by bacteria of the genus Salmonella. The bacteria are mostly ingested through food, i.e., when eating. 

In Germany, this foodborne infection occurs primarily after eating eggs that have not been heated sufficiently or food containing eggs. Infected persons typically have diarrhea. Antibiotics should only be used for certain risk groups when treating salmonellosis.

The symptoms of salmonella infection are similar to those of acute intestinal inflammation. There is sudden onset of diarrhea, headache, abdominal pain, indisposition, and sometimes vomiting. A slight fever often occurs. The symptoms can last for several days and then subside on their own.

If severe diarrhea persists for a long time, there may be a significant loss of fluid (dehydration), in which important salts are also lost. This further impacts a person’s general condition. In infants, young children, and the elderly, severe fluid and salt loss can quickly lead to circulatory collapse and become life-threatening. 

In rare cases, the inflammation spreads from the intestine to other organs and leads to high fever (septic course).

Salmonellosis is a diarrheal disease caused by the bacterium Salmonella enterica. It is one of the classic foodborne infections. It is different from typhoid and parathyphoid that are caused by other salmonella species and are usually accompanied by fever and severe illness. Most affected individuals in Germany usually bring it back from travels.

In most cases, the salmonellosis pathogens enter the body through infected food. However, infection is also possible from person to person or from animal to human.

Infection through food containing eggs

In Germany, the most widespread salmonella species is Salmonella enteritidis. It is transmitted primarily through raw or insufficiently heated eggs, or food containing eggs. 

Infection through meat

The Salmonella species Salmonella typhimurium is transmitted through raw meat or meat products that have not been heated or have not been heated sufficiently, such as minced meat or Mettwurst sausage spread.

Infection from person to person

Infection from person to person can occur through a smear infection, especially if hygiene is inadequate. In this case, the bacteria from the intestine are passed on via the smallest traces of stool residues on the hands of infected persons. Infection can also occur via contaminated surfaces and contaminated food.

Infection from animal to human

Infections through direct contact with domestic animals are rare. Animal owners are most likely to become infected via the animals’ feces. Surfaces contaminated with feces can also be a source of infection.

Other, rarer cases of infection in Germany

Other, rarer sources of infection for Salmonella that have occurred in Germany include:

• herbal tea  
• chocolate 
• smoked eel 
• mung bean sprouts 
• melons 

Plant foods can also contain salmonella.

In most people, symptoms last only a few hours or days. For certain risk groups, however, salmonellosis can sometimes be dangerous, for example, if it leads to severe fluid and salt loss or spreads in the body beyond the intestine. This can lead to longer and more severe courses of the disease.

These risk groups include: 

• infants
• older people
• people with pre-existing conditions

It is also possible that taking antacid medications increases the risk of contracting the disease. However, the data on this is not clear.

Salmonella infections are common worldwide. Illnesses occur as sporadic cases, clusters of cases, such as in families, or as larger outbreaks. In 2018, there were 274 outbreaks in Germany with more than 1,000 people affected. Eggs from barn-raised hens and Spaetzle noodles were the most common triggers.

Since mandatory vaccination of laying hens, broilers, and turkeys was introduced in 2008, the number of Salmonella enteritidis infections in humans has decreased significantly.

There were 13,529 cases of salmonella poisoning in Germany in 2018. About a third of these were acquired in countries visited for vacation. Many infections occur in late summer. Children under 5 years of age are most frequently affected. Deaths are rare in Germany. 

After a person becomes infected, symptoms appear within 6 to 72 hours, usually 12 to 36 hours (known as the incubation period). Typically, the disease progresses without complications.  

Mild cases

Salmonellosis begins as an acute intestinal inflammation with the symptoms of a gastrointestinal infection. The symptoms subside on their own within 2 to 3 days.

Severe case 

In rare cases, intestinal inflammation can spread to other organs. 

Possible complications are:

• inflammation of the joints
• gall bladder inflammation
• inflammation of the innermost layer of the heart (endocardium) and heart valves
• meningitis
• pericarditis
• pneumonia
• skin disorders, skin conditions
• inflammation of the renal pelvis and kidneys

If severe, salmonellosis should be treated with antibacterial drugs (antibiotics). Some patients need to be treated in the hospital.

Fewer than one in 1,000 people die from salmonellosis. Those most at risk are the elderly and people with weakened immune systems.

Salmonella multiplies in a temperature range between 10 and 47 degrees, and in some cases as low as 6 to 8 degrees. It can survive for several months in its surroundings and in or on various foods. 

Food handling 

The following measures will reduce the risk of Salmonella infection:

• All foods and foodstuffs that contain a lot of protein and water must either be heated above 70 degrees or stored in the refrigerator. 
• Salmonella can be reliably killed at temperatures above 70 degrees and at least 10 minutes cooking time.
• Raw meat and sausage products, slaughtered poultry, sea animals, eggs, creams, salads, and mayonnaises with raw egg, as well as ice cream, belong in the refrigerator.
• The cooling time must be kept short for precooked foods. Hot foods should be consumed within 2 hours of the last time they were heated.
• When thawing frozen poultry and game, the resulting water often contains salmonella. It should therefore be collected separately and disposed of immediately. All items that came into contact with it should be thoroughly cleaned with hot water immediately afterwards. Hands must be washed.
• Food should be heated in the microwave for a sufficient amount of time. When reheating food, an inner temperature of 70 degrees must be exceeded.
• Ready-made products such as pudding, baking mixes, or packaged soups should be prepared just before consumption.
• Instant baby food should be prepared with water of at least 70 degrees, then allowed to cool quickly and consumed within 2 hours.

The Bundesinstitut für Risikobewertung (Federal Institute for Risk Assessment) has compiled further information on protection against foodborne infections in private households.

Hygiene when cooking

• Wash hands thoroughly with soap after contact with food potentially containing salmonella.
• Change kitchen towels frequently and wash them at a minimum temperature of 60 degrees.

Prevention in kindergartens, schools, and homes

The most important precaution is hand washing. This is especially true after using the toilet, after contact with suspected infected items such as diapers, and food such as poultry, and before preparing meals.

Avoiding infection by affected persons

• Sick persons with symptoms are usually not able to work and should stay home.
• Sick children under 6 years of age should not visit community facilities such as kindergartens and daycare centers, schools or homes. Once recovered, they must be symptom-free for 2 days before returning. Parents must inform community facilities of their child’s illness.
• Persons suspected of having salmonellosis, who are ill, or who are shedding salmonella are temporarily prohibited from working in certain areas of food establishments or community food service facilities.

Further information on what to do in the event of a salmonella infection is provided in various languages by the Bundeszentrale für gesundheitliche Aufklärung (Federal Center for Health Education) on its website infektionsschutz.de.

If salmonellosis is suspected, the following specimens may be tested:

• stool, feces 
• vomit 
• suspicious food
• blood (in severe cases)

It takes 2 to 3 days to identify precisely the causative bacterial type. However, with the help of various rapid diagnostics, a preliminary diagnosis can be made within one day.

If inflammation occurs in other organs beyond the intestine, salmonellosis must be treated with antibacterial drugs (antibiotics).

To avoid complications in high-risk patients, antibiotics may be used even if the case is mild. 

High-risk groups are:   

• babies in the first year of life 
• older people
• persons with congenital or acquired immunodeficiency 
• patients with known damage to the heart valves or blood vessels.