The number of foodborne infections in the Netherlands in 2020 fell sharply compared with previous years likely because of measures taken against coronavirus, researchers say.

Closures of cafes and restaurants, the decrease in social events including catering, travel restrictions, social distancing and increased attention to hygiene such as washing hands, reduced the contact between people and pathogens. Another reason for the decline in numbers is that people with gastrointestinal infections were probably less likely to seek medical help, according to a report published by the National Institute for Public Health and the Environment (RIVM).

Reports of norovirus and rotavirus decreased in 2020, with 56 percent and 68 percent fewer infections, respectively, than in 2019. These viruses are spread mainly through human-to-human transmission but are also spread through contaminated food and food surfaces and utensils.

Campylobacter and Salmonella findings
Food-related infections such as salmonellosis and campylobacteriosis also declined significantly but the number of people who became ill with listeriosis was unchanged.

It is estimated the number of campylobacteriosis cases was 3,942 based on 2,549 reports in a system that has a national coverage rate of 65 percent. These are the lowest numbers in a decade. The amount of people sick in 2019 was more than 6,000.

The percentage of highly contaminated poultry flocks at slaughter fell to 34 percent in 2020 after several years of going up. Highly contaminated means more than 10,000 colony forming units per gram. The percentage of contaminated fresh chicken meat increased to 40 percent of 232 samples.

There were 888 estimated salmonellosis cases, which is based on 568 lab-confirmed cases with 64 percent national coverage. This is the lowest since surveillance began in the 1990s. The number of lab-confirmed patients in 2019 was more than 1,000.

As in previous years, Salmonella Enteritidis, Typhimurium and monophasic Typhimurium were the main causes of salmonellosis. The relative share of Salmonella Enteritidis decreased sharply, probably because of a decline in travel-related salmonellosis and the closure of catering operations. Pork and egg products remained the main source of Salmonella infections.

A rise in Salmonella Virchow cases was investigated. Since October 2019, 15 people are part of the same whole genome sequencing cluster. Patient samples matched six food isolates from chicken meat in 2018 and 2019, which came from different goods with no relationship between the companies involved.

More Salmonella Manhattan cases were also seen, with nine people belonging to the same WGS cluster in September and October 2020, compared to an average of two per year from 2016 to 2019. However, no outbreak investigation was started because officials said the chance of finding a common food source with this number of patients was limited. In 2021, WGS was started for all Salmonella serotypes. This led to more clusters being found and more outbreak investigations opened.

Researchers find E. coli O104 isolate was linked to 2011 outbreak
In 2020, 323 people with a Shiga toxin-producing E. coli (STEC) infection were reported. This is the lowest since 2011 and below the 460 infections in 2019.

Eight patients developed hemolytic uremic syndrome (HUS) and two men died directly or indirectly as a result of STEC infection.

Out of 250 people who contracted infection in the Netherlands, almost all of them ate meat and nearly half had eaten raw or undercooked meat. Ten percent of 222 sick people had consumed raw milk.

From submitted patient isolates, STEC O157 was most commonly detected, followed by STEC O26, STEC O103 and STEC O145. In total, 23 different O-groups were found. The most notable finding, researchers said, was a STEC O104 isolate linked to the 2011 E. coli O104 outbreak in Germany.

Listeria infections and brucellosis
In 2020, 95 individuals were reported with listeriosis. At least 92 were hospitalized and 19 people aged 38 to 98 died. The median age of all patients was 75 years old with a range of 29 to 98 and 62 percent were male. In 2019, 117 cases were recorded.

The fact that, compared to other foodborne infections, there was no decrease in listeriosis can be explained by the fact that surveillance is mainly focused on very serious cases and infection is also mainly contracted at home through contaminated food products, said experts.

Three patients with brucellosis were reported, of which two infections were contracted in Turkey and one in the Netherlands. Two people were hospitalized. Consumption of raw milk cheese was the most likely source for the Dutch case and one Turkish case.

A previous report revealed there were 559 outbreaks in 2020 with 1,907 patients.

A Salmonella Enteritidis outbreak with 56 patients in August 2020 was linked to Turkish pizza from one catering business. The incident initially affected an institution for the mentally and physically disabled but more cases were then identified in the general population. There was a major outbreak of norovirus with 63 sick related to a buffet on a boat and three smaller outbreaks of listeriosis linked to trout fillets, eel and soft cheese.

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