Beware of raw Indian curry leaves! British health authorities have advised the public to cook curry leaves thoroughly if they are to be used in recipes as using them raw, may risk infection.

The authorities issued the advice as they found the raw curry leaves, used in a 'chutney', contaminated with Salmonella bacteria causing Diarrhoea and vomiting to more than 400 people at a street-food festival in Newcastle, north-east England in February.

An investigation by Public Health England (PHE) and Newcastle City Council found 25 of the 29 cases had developed a strain of salmonella never found in people or food in the UK before.

"This was one of the largest outbreaks of gastro-intestinal illness associated with herbs or spices in the country.

In addition, it was the first time one of the strains of Salmonella was detected in the UK," said Dr Kirsty Foster, chair of the outbreak control team and consultant in health protection with PHE.

"We have reported our findings to the Food Standards Agency, recommending that advice is developed for the food industry and the public about the use of raw curry leaves.

While this is being developed, our advice to the public is to cook curry leaves thoroughly if they are to be used in recipes and to be aware of the risk of infection if using them raw," she added.

The leaves were contaminated with several different bacteria, experts found, which led to 29 confirmed cases of salmonella.

However, there will be no prosecution in the case because there was seen to be a lack of clear advice about the dangers of using raw curry leaves in recipes, and in general hygiene levels at the three-day event were declared to be good.

"It has been a really, really thorough investigation and the council has been very helpful. People do eat curry leaves raw and if some good can come from this it is the awareness that has been raised about eating raw curry leaves," said Bob Arora, the British-Sikh owner of Sachins Punjabi restaurant in Newcastle and one of the organisers of the festival.

The event raised nearly USD 17,000 for Brain Tumour UK in memory of his brother-in-law Kuly Ral, who died from the disease.