More than 250 people are sick in an E. coli O157 outbreak in the United Kingdom that may have been caused by salad.

There have been 259 confirmed cases in the UK with sample dates ranging from late August to the end of October, although most people fell ill in August and early September.

Shiga toxin-producing E. coli (STEC) O157 has affected people in England, Scotland, Northern Ireland, and Wales. The majority of those sick are adults.

Food Standards Scotland (FSS), the UK Health Security Agency (UKHSA) and Food Standards Agency (FSA) are investigating the outbreak.

It is the largest E. coli outbreak since Whole Genome Sequencing (WGS) started to be used in 2014, according to UKHSA.

Produce link but investigation ongoing
The number of patients is up from 192 in September when health officials said there had been no deaths and no reported cases of the hemolytic uremic syndrome (HUS). HUS is a type of kidney failure associated with E. coli infections that can result in lifelong, serious health problems and death.

Some patients have been interviewed to try to find the source of the infection. Investigations suggest UK-produced lettuce and salad leaves may be implicated but this has yet to be /confirm/ied.

Dr. Lesley Larkin, head of surveillance, gastrointestinal infections, and food safety at UKHSA, said the increase in reports was driven by a particular strain of E. coli O157.

“Making sure you wash your hands with soap and water is the best way to stop this bug from spreading. When preparing food make sure you thoroughly wash salad, fruit, and vegetables and follow all the safe cooking instructions for meat,” she said.

Earlier this year, a STEC O103 outbreak with 11 cases was associated with raw milk cheese from a dairy farm in the East of England, and a STEC O145 outbreak with 10 patients was linked to milk products from a farm in North West England.

about E. coli infections
Anyone who has developed symptoms of E. coli infection should seek medical attention and tell their doctor about their possible food poisoning. Specific tests are required to diagnose the infections, which can mimic other illnesses.

The symptoms of E. coli infections vary for each person but often include severe stomach cramps and diarrhea, which is often bloody. Some patients may also have a fever. Most patients recover within five to seven days. Others can develop severe or life-threatening symptoms and complications, according to the Centers for Disease Control and Prevention (CDC).

about 5 to 10 percent of those diagnosed with E. coli infections develop a potentially life-threatening kidney failure complication, known as a hemolytic uremic syndrome (HUS). Symptoms of HUS include fever, abdominal pain, feeling very tired, decreased frequency of urination, small unexplained bruises or bleeding, and pallor. 

Many people with HUS recover within a few weeks, but some suffer permanent injuries or death. This condition can occur among people of any age but is most common in children younger than five years old because of their immature immune systems, older adults because of deteriorating immune systems, and people with compromised immune systems such as cancer patients. 

People who experience HUS symptoms should immediately seek emergency medical care. People with HUS will likely be hospitalized because the condition can cause other serious and ongoing problems such as hypertension, chronic kidney disease, brain damage, and neurologic problems.