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High season for salmonella and campylobacter

32/2016, 16.08.2016

Scientific study proves link between increasing ambient temperatures and prevalence of bacterial infections

Summertime is germ time: as the temperature increases, the number of illnesses caused by bacteria goes up too. In Germany alone, 13,823 salmonella infections and 70,190 campylobacter infections were reported last year to the Robert Koch Institute. Both types of germs are typical pathogens which may also be found in foods. “During the warm time of the year, food and kitchen hygiene is especially important to avoid illnesses”, says Professor Dr. Dr. Andreas Hensel, President of the German Federal Institute for Risk Assessment (BfR). The time correlation between increasing ambient temperature and rising numbers of infections from salmonella and campylobacter has now been demonstrated by a scientific publication in Nature’s journal Scientific Reports. The BfR notably contributed the statistical analysis to this publication (doi:10.1038/srep28442).

Over a time period of four years, the scientists analysed data on ambient temperature and data on the prevalence of salmonellosis and campylobacteriosis collected in the cities of Berlin and Munich as well as three rural areas in Germany. The comprehensive statistical analysis shows a time correlation between an increase in temperature and a rise in the number of infections caused by salmonella and campylobacter. Thus a connection between the number of cases of Salmonella S. enteritidis infection and the average temperature three weeks prior to the cases of infection could be established.

Salmonella are known for multiplying quickly in high temperatures. Sufficient chilling of animal and highly perishable foods is therefore especially important when outside temperatures are high. In addition, the fact that consumers often neglect to implement the rules of hygiene when grilling outdoors also accounts for an increase in salmonella infections during the summer months. Thus, for example, pathogens can be transferred from raw meat to salad. Additionally, foods are often not sufficiently chilled during picnics and barbecues.

The seasonal increase in campylobacter infections may in part be attributable to the increased activity of flies in the warmer weeks. It is known that flies can spread the pathogen within animal populations, especially poultry populations.

The finding of the study shows clearly that when producing and preparing foods, hygienic measures should be observed more strictly during the warm time of the year.

The full version of the article is published online on

The BfR provides extensive information on the protection against foodborne infections for consumers:

At the start of the grilling season, the institute additionally published, as part of its “100 seconds BfR” series, the film “Safe Grilling”:

About the BfR

The German Federal Institute for Risk Assessment (BfR) is a scientifically independent institution within the portfolio of the Federal Ministry of Food and Agriculture (BMEL) in Germany. It advises the Federal Government and Federal Laender on questions of food, chemical and product safety. The BfR conducts its own research on topics that are closely linked to its assessment tasks.


This text version is a translation of the original German text which is the only legally binding version.


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