Public health officials in England and Wales are investigating the source of a Salmonella outbreak that has sickened more than 50 people.

Public Health England (PHE), Public Health Wales (PHW) and the Food Standards Agency (FSA) are looking into the Salmonella 4,[5],12:b:- outbreak that could be linked to food served at some Indian restaurants.

It was identified through routine surveillance that identifies increased reports of Salmonella serotypes and through analyzing data obtained through whole-genome sequencing (WGS).

A PHE spokeswoman told Food Safety News there is no evidence of people ill who live outside of England and Wales and that the agency is not aware of any deaths associated with the outbreak.

Illnesses in Wales and England

A total of 54 patients have been reported, with sample dates ranging from April 23 to July 7, 2019. Six cases have been recorded during May, 23 in June and another 25 in July.

The age of those affected ranges from 14 months to 80 years with half of them aged 20 to 40. Twenty are female and 28 male. Twelve cases are from Wales and 42 from England.

Dr. Nick Phin, deputy director at the National Infections Service of PHE, said the agency is investigating a number of cases of Salmonella that have occurred in different parts of England and Wales.

“We have established a link between the cases based on the analysis of data obtained through whole-genome sequencing and we are working with the Food Standards Agency and health protection colleagues in Wales to determine the possible cause of the infection,” he said.

“There are simple steps to limit the spread of Salmonella, such as hygienic handling and preparation of food including cooking food thoroughly. Salmonella can also be spread from person to person, so anyone affected should adhere to good hygiene practice such as washing your hands thoroughly after using the bathroom.”

From 2013 to 2018 there were 45 cases of Salmonella enterica serotype 4,5,12:b:- reported per year on average.

link to Indian restaurants

An EU-wide query through the Epidemic Intelligence Information System (EPIS) has been posted but it is not thought the outbreak affects other countries.

While no common food product has yet been identified, several people ate at various Indian restaurants in England and Wales in the week prior to illness onset. Two Indian restaurants in London have been identified wher multiple confirmed cases reported eating before becoming ill and investigations are ongoing.

To identify the outbreak source and allow the FSA to follow up restaurant supply chain information, an outbreak control team (OCT) has created a hypothesis-generating questionnaire for cases.

“OCT members are collecting information from patients and potential venues to identify a likely source of the outbreak. Any venues are followed up by local authority environmental health teams as per their protocols,” said the PHE spokeswoman.

Isolates are sensitive to all antimicrobials tested, apart from one strain that is ampicillin resistant.

Symptoms of Salmonella infection usually appear 12 to 72 hours after infection and include fever, abdominal pain, diarrhea, nausea and sometimes vomiting.

The illness can last four to seven days but most people recover without treatment. Symptoms may be more serious in young children, pregnant women, immunocompromised individuals, and the elderly.