Thousands of Britons become unknowingly infected with a little-known bug each year, health chiefs have warned.
Yersinia enterocolitica – common in the 1980s and 1990s – can cause week-long diarrhea. While most cases are mild, it can be fatal.
It is usually spread by eating contaminated pork that has not been cooked properly.
Only 8,023 laboratory-confirmed cases of the foodborne illness were recorded in England between 1975 and 2020, leading some experts to believe that cases were declining.
But researchers linked to the UK Health Security Agency (UKHSA) believe this is wrong and 7,500 Britons could be affected each year.
Yersinia enterocolitica, common in the late ’80s and ’90s, usually causes weeks of diarrhea. It is one of the most common bacterial foodborne agents in Europe and is often spread through eating contaminated food, especially raw or undercooked pork products, or through contact with a person who has prepared a pork product.
Researchers found that 8,023 lab-confirmed Yersinia infections were recorded in England between 1975 and 2020, most of which were caused by Yersinia enterocolitica. The number of cases rose “sharply” in the 1980s, peaking in 1988 and 1989 before tapering off, they noted. Between 2017 and 2020, reported cases rose in one diagnostic laboratory, the Portsmouth Hospitals NHS Trust microbiology laboratory in Hampshire, accounting for around 60 per cent of all 546 reported patients in England. This followed the implementation of routine PCR testing for Yersinia, researchers said
The decline in recent decades has been largely attributed to outbreaks of foot and mouth disease, which reduced pork consumption, and improved hygiene in slaughterhouses.
To get an idea of the true picture in the UK, scientists examined data on Yersinia cases in England between 1975 and 2020.
Write in the journal Eurosurveillancethey said: ‘Our examination of the available data provides good evidence that yersinia infection is substantially under-reported in England’.
There are also “real changes in the epidemiology of this infection that have gone unnoticed,” they added.
In addition to diarrhea, common symptoms of the bacterial infection include abdominal pain, headache, and fever.
Joint and back pain, muscle pain, dizziness and blood in the stool have also been reported.
But routine testing for yersinia is not currently recommended in the UK unless doctors believe patients may be suffering from diseases such as appendicitis, mesenteric lymphadenitis, terminal ileitis or reactive arthritis, which present with similar symptoms to the bacterial infection.
“There is a compelling case for a structured approach to yersinia surveillance in England and other countries,” the researchers wrote.
“That includes routine testing and case follow-up through epidemiological questionnaires.”
The experts found that 8,023 cases of Yersinia were recorded in England between 1975 and 2020, most of which were caused by Yersinia enterocolitica, as opposed to the bacteria Yersinia pseudotuberculosis, which belongs to the same family.
Cases rose “sharply” in the 1980s, peaking in 1988 and 1989 before declining, they noted.
The incidence subsequently remained low until 2016.
While researchers did not give reasons why infections peaked in the 1980s, they acknowledged that reported cases of yersinia may have declined in the 2000s “due to the impact of foot-and-mouth disease outbreaks on pork consumption.”
Better hygiene in slaughterhouses could also have influenced the total number of reported infections.
The decline in recorded reports of yersinia from laboratories across England also coincided with the introduction of Clinical Pathology Accreditation in the early 1990s, which assesses clinical standards and procedures in laboratories, they noted.
But “the current and historically recorded incidence of laboratory-confirmed yersinia infection in England is largely driven by variable testing patterns,” researchers said.
“In general, low levels may not reflect the true incidence of infection.”
Between 2017 and 2020, reported cases rose in one diagnostic laboratory, the Portsmouth Hospitals NHS Trust microbiology laboratory in Hampshire, accounting for around 60 per cent of all 546 reported patients in England.
This followed the implementation of routine PCR testing for yersinia, researchers said.
If the same PCR incidence tests were consistent across laboratories in England, the team estimated that an average of 7,500 Yersinia enterocolitica infections could go undiagnosed each year between 2017 and 2020.
However, they acknowledged that this was based on results from a single lab, so the actual magnitude of yersinia infections could vary.
“This is based on extrapolation from only one area and the incidence may vary between regions and years,” they said.
In 2021, a total of 6,876 confirmed cases of yersinosis were reported by 28 countries of the European Union or the European Economic Area.
This means an overall rate of 1.9 cases per 100,000 inhabitants.
However, the researchers said there was a “markedly variable incidence” of Yersinia cases across Europe, which may reflect, in part, “differential testing practices and substantial uncertainty in many other countries.”
While Denmark and Finland recorded the highest cases, Romania and Bulgaria recorded the fewest.