A report published by the Swedish Food Agency (Livsmedelsverket) compiles and analyzes reported suspected foodborne illnesses in Sweden from 2019 to 2023.

In the report, foodborne illness is defined as disease caused by microorganisms, toxins, histamines, or lectins in food, excluding drinking water. 

“By analyzing data over time, we gain insights into the current state, trends, and risk factors for foodborne illnesses in Sweden,” the Swedish Food Agency (SFA) says. “It also helps estimate how many are affected and which food groups contribute most, enabling risk reduction.”

Municipal control authorities, together with infectious disease control units, county administrative boards, and the Public Health Agency of Sweden, are required to investigate foodborne outbreaks and report the results to SFA as soon as possible. 

During the period, 142 of Sweden’s 290 municipalities reported foodborne illnesses to SFA. A total of 1,621 incidents, covering 10,139 illness cases, were reported. On average, this corresponds to 324 reports and 2,027 illness cases per year, which is lower than the figures for the previous five-year period (2014–2018), during which on average 434 reports covering 3,573 illness cases per year were recorded. 

The decrease can partly be explained by a large campylobacteriosis outbreak during the preceding period (in 2016–2017) and the restrictions during the COVID-19 pandemic (2020–2022), which led to reduced transmission of microbial infections in society, including foodborne illnesses.

In 80 percent of all reports, the microorganism or substance that caused the foodborne illness could not be identified. Bacteria, bacterial toxins, or histamines were indicated as the cause in 11 percent of reports, while viruses and parasites (Cryptosporidium) accounted for 7 percent and 1 percent of the reports, respectively. Among reported illness cases, 45 percent were from outbreaks with an unknown agent. Bacteria and viruses each accounted for about 20 percent of cases, while parasites caused 7 percent of the cases. Nine reports during the 2019–2023 period concerned foodborne illnesses involving lectins or marine biotoxins.

For most of the reported foodborne illnesses, the food involved was unknown. For those foodborne illnesses where a specific food item was identified, vegetables represented the single largest food category in terms of reported illness cases, followed by composite meals, seafood, and buffet food. Altogether, plant-based food categories accounted for 57 reports and 1,925 illness cases. The corresponding figures for animal-based food categories were 200 reports and 1,397 cases. Other food categories (excluding unknown food) accounted for 187 reports and 1,803 cases.

Among the reports where the cause was specified, caliciviruses (mainly norovirus) caused the highest number of illness cases (112 reports, 2,308 illness cases). Foodborne illnesses involving calicivirus were reported throughout the year, but the number of illness cases was higher in winter−spring, peaking in March, which coincides with the seasonal pattern for winter vomiting disease. 

Composite meals, seafood (especially oysters), and buffet food were most frequently identified in calicivirus outbreaks. In most cases, the transmission was caused by infected individuals handling the food during preparation. In the case of oysters, they had been contaminated with calicivirus in the production area.

Salmonella also caused many illness cases (33 reports, 749 illness cases), most of which occurred in late summer and autumn. Salmonella was identified as the cause of contamination in a variety of both animal and plant-based foods. Plant-based foods were identified as the source of more illness cases than animal-based foods, consistent with the previous compilation. 

In total, 15 serotypes of Salmonella were present in the reports. Salmonella Enteritidis was the most reported serotype and caused the second highest number of cases. Salmonella Typhimurium, including monophasic Salmonella Typhimurium, was the serotype infecting the highest number of people. 

Cryptosporidium was the third most frequently identified pathogen (20 reports, 697 illness cases). Leafy greens, especially kale, were a common source of contamination. There is a long-term trend of an increase in the reporting of outbreaks and foodborne illnesses involving Cryptosporidium. A continued increase was seen in the analyzed period. The increase can partly be attributed to increased awareness of the pathogen within healthcare and to improved diagnostic methods, but also to increased consumption of kale and other leafy greens. 

The full version of the SFA publication was produced in Swedish. While only the title and summary have been translated into English, additional SFA findings included in the English-language summary can be found here.