Category Archives: Yersinia

Research – Yersinia enterocolitica Outbreak Associated with Pasteurized Milk

Mary Ann Liebert

In July 2019, we investigated a cluster of Yersinia enterocolitica cases affecting a youth summer camp and nearby community in northeastern Pennsylvania. After initial telephone interviews with camp owners and community members, we identified pasteurized milk from a small dairy conducting on-site pasteurization, Dairy A, as a shared exposure. We conducted site visits at the camp and Dairy A where we collected milk and other samples. Samples were cultured for Y. enterocolitica. Clinical and nonclinical isolates were compared using molecular subtyping. We performed case finding, conducted telephone interviews for community cases, and conducted a cohort study among adult camp staff by administering an online questionnaire. In total, we identified 109 Y. enterocolitica cases. Consumption of Dairy A milk was known for 37 (34%); of these, Dairy A milk was consumed by 31 (84%). Dairy A had shipped 214 gallons of pasteurized milk in 5 weekly shipments to the camp by mid-July. Dairy A milk was the only shared exposure identified between the camp and community. Y. enterocolitica was isolated from Dairy A unpasteurized milk samples. Five clinical isolates from camp members, two clinical isolates from community members, and nine isolates from unpasteurized milk were indistinguishable by whole-genome sequencing. The risk for yersinosis among camp staff who drank Dairy A milk was 5.3 times the risk for those who did not (95% confidence interval: 1.6–17.3). Because Dairy A only sold pasteurized milk, pasteurized milk was considered the outbreak source. We recommend governmental agencies and small dairies conducting on-site pasteurization collaborate to develop outbreak prevention strategies.

Korea – Food poisoning bacteria found in 15 kimchi products from China

Korean Times

Yersinia p

Food poisoning bacteria were detected in 15 out of 289 kimchi products imported from China, according to the Ministry of Food and Drug Safety, Tuesday.

Two out of four Chinese salt-cured cabbage products were also found to have used preservatives that are not permitted in Korea.

It examined the 289 products from 55 Chinese companies imported here, and detected Yersinia enterocolitica, a type of food poisoning bacteria, in 15 of them.

Norwegian – Disease-causing Yersinia enterocolitica in pork products – 2019


Yersinia p

On behalf of the Norwegian Food Safety Authority, the Norwegian Veterinary Institute has analyzed a total of 152 samples of minced pork and pork dough for Yersinia enterocolitica, a bacterium in which some varieties are capable of causing disease in humans. Pigs are considered to be the main reservoir for pathogenic Y. enterocolitica, and pork is considered an important source of infection.

What we investigated: A total of 152 samples of minced pork and pork dough were analyzed.
Period: 2019
What we were looking for: Yersinia enterocolitica
What we found:
  • The results indicate that the incidence of pathogenic Y. enterocolitica in Norwegian pork products is low, but that they may occur.
  • It is therefore important to fry pork products well and not to taste raw products such as pork dough, bacon and the like. Also remember good kitchen hygiene when handling raw meat.
  • Since it has been a long time since the previous survey took place and the surveys are not directly comparable, this survey provides updated knowledge for the benefit of both industry, authorities and knowledge institutions.

Sweden – Yersinia enterocolitica outbreak over, Iceberg lettuce is the suspected source

Outbreak News Today

The Swedish Public Health Agency says the outbreak of Yersinia enterocolitica is over.

During the period January and up to the beginning of February, twice as many people fell ill with Yersinia infection as during the same period in a normal year. Of a total of 53 cases of Yersinia enterocolitica, 33 were resident in the regions of Stockholm, Västra Götaland and Halland.

Isolates from 24 of these cases were typed by whole genome sequencing, ie analysis of the bacterium’s genome, and 16 outbreak cases with clustered isolates could be identified.

The Swedish Public Health Agency and the infection control units have collaborated on interviews with sick people and compilation of questionnaire responses about what and where they ate before the illness. A so-called case-case study where questionnaire responses from outbreak cases were compared with questionnaire responses from disease cases with Yersinia infection that did not belong to the outbreak, it emerged that the outbreak cases had to a greater extent visited one and the same restaurant chain.

A contaminated batch of iceberg lettuce distributed to a restaurant chain is the suspected source of infection.

Sweden – Yersinia (Sweden, January 2021–) – Increase in cases of yersinia infection.


Since the second week of January, more than twice as many people have contracted yersinia infection as during the same period in the immediately preceding years. An increased number of patients has mainly been observed in the regions of Stockholm, Västra Götaland and Halland, which together account for 33 of the total of 48 disease cases reported since 11 January. Of the patients, a majority are aged 11-40 and most are women (figure). In the ongoing investigation, the Swedish Public Health Agency collaborates with the infection control units in the affected regions to try to identify the source of the infection through interviews of the cases and surveys.

As part of the outbreak investigation, the Swedish Public Health Agency also collects yersinia isolates from disease cases in the affected regions. The isolates are typed using whole genome sequencing (analysis of the genome of the bacterium) to clarify who has been affected by a common source of infection.

Figure. Distribution by age and sex of persons reported to be infected with yersinia infection 11 January – 2 February 2021.

Figure.  Distribution by age and sex of persons reported to be infected with yersinia infection 11 January – 2 February 2021.

New Zealand – Yersiniosis in New Zealand


The rate of yersiniosis in New Zealand (NZ) is high compared with other developed countries, and rates have been increasing over recent years. Typically, >99% of human cases in NZ are attributed to Yersinia enterocolitica (YE), although in 2014, a large outbreak of 220 cases was caused by Yersinia pseudotuberculosis. Up until 2012, the most common NZ strain was YE biotype 4. The emergent strain since this time is YE biotype 2/3 serotype O:9. The pathogenic potential of some YE biotypes remains unclear. Most human cases of yersiniosis are considered sporadic without an identifiable source. Key restrictions in previous investigations included insufficient sensitivity for the isolation of Yersinia spp. from foods, although foodborne transmission is the most likely route of infection. In NZ, YE has been isolated from a variety of sick and healthy domestic and farm animals but the pathways from zoonotic reservoir to human remain unproven. Whole-genome sequencing provides unprecedented discriminatory power for typing Yersinia and is now being applied to NZ epidemiological investigations. A “One-Health” approach is necessary to elucidate the routes of transmission of Yersinia and consequently inform targeted interventions for the prevention and management of yersiniosis in NZ View Full-Text

Sweden – Sweden reports increase in Yersinia cases

Outbreak News Today

Yersinia p

The Swedish Public Health Agency, or Folkhälsomyndigheten reports an increase in cases of Yersinia infections since the second week of January, according to a February 3 release.

They say more than twice as many people have contracted Yersinia infection as during the same period in the immediately preceding years.

An increased number of patients has mainly been observed in the regions of Stockholm, Västra Götaland and Halland, which together account for 33 of the total of 48 disease cases reported since 11 January.

Europe – Yersiniosis – Annual Epidemiological Report for 2019


Yersinia p

For 2019, 29 countries reported 7 048 confirmed yersiniosis cases in the EU/EEA. The overall notification rate of 1.7 per 100 000 population remained stable from 2015 to 2019. The highest rates were reported by Finland, Lithuania and Czechia. The highest rate was detected in 0–4 year-old children, with 7.2 per 100 000 population for males and
5.9 per 100 000 population for females.


Research – Impact of a Combination of UV-C Irradiation and Peracetic Acid Spray Treatment on Brochothrix thermosphacta and Yersinia enterocolitica Contaminated Pork


Efficient ways of decontamination are needed to minimize the risk of infections with Yersinia (Y.) enterocolitica, which causes gastrointestinal diseases in humans, and to reduce the numbers of Brochothrix (B.) thermosphacta to extend the shelf-life of meat. While many studies have focused on a single treatment of peracetic acid (PAA) or UV-C-irradiation, there are no studies about a combined treatment on meat. Therefore, in the present study, pork was inoculated with either Y. enterocolitica or B. thermosphacta, and was treated with a combination of 2040 mJ/cm2 UV-C irradiation followed by a 2000 ppm PAA spray treatment (30 s). Samples were packed under modified atmosphere and stored for 1, 7, or 14 days. The samples were examined for Y. enterocolitica and B. thermosphacta content, chemical and sensory effects, and meat quality parameters. For Y. enterocolitica, a significant reduction of up to 2.16 log10 cfu/cm2 meat and for B. thermosphacta, up to 2.37 log10 cfu/cm2 meat was seen on day 14 after UV-C/PAA treatment compared to the untreated controls.

Norway – Yersinia outbreak in Norway linked to salad

Food Safety News

Yersinia p

A Yersinia outbreak in Norway has been solved and declared over just days after it was announced.

Folkehelseinstituttet (the Norwegian Institute of Public Health) said the national outbreak of Yersinia enterocolitica O3 was likely caused by a pre-mixed salad product.

Less than a week earlier, the agency had announced an investigation into a recent rise in Yersinia infections.

The outbreak started in mid-November and involved 10 confirmed patients. All of them are women aged 11 to 59 years old who became ill in mid to late November with the last case on Nov. 26. Three people live in Viken, two each in Oslo, Innlandet, and Vestland, and one in Telemark and Vestfold.