AN investigation into the outbreak of E coli O55 in Dorset is still no closer to identifying the source.

The rare strain of the pathogen was first identified in the county in July last year and since then some 30 people have developed symptoms, with several hospitalised with life-threatening haemolytic uraemic syndrome (HUS).

Noëleen McFarland, consultant in health protection for Public Health England, which is carrying out the investigation, said identifying the source had proven unusually difficult.

"Normally we would have been able to identify a source because our investigation would have found some commonalities," she said.

"The only commonality in these cases is they live in, have contact with people in, or have travelled through Dorset."

The agency has not revealed the locations where outbreaks have occurred, however several Bournemouth families were affected last year including four-year-old Isaac Mortlock, along with children at a nursery in Blandford.

Field epidemiologists have been interviewing victims and their families and, with the aid of local authority environmental health teams, quizzing people they have had contact with in the fortnight prior, including schools and places of work, restaurants and supermarkets.

In some cases stool and blood samples have been taken for testing in the agency's lab at Porton Down, Wiltshire. The data is then mapped to identify common elements which might pinpoint a cause.

Investigators found the strain in cats owned by some infected families, but unusually no trace has been found in cattle or sheep, the vector of the more common E coli O157 strain - which has similar symptoms and affects around 50 people a year in the Wessex region.

While previously unknown in the UK, E coli O55 has previously been identified in Ireland, France and Italy, but only in isolated cases with no general outbreak. It does not always show symptoms and in some cases where it does they will resolve without medical treatment.

"It is very important that we identify a source, particularly as this is unique to the UK" said Ms McFarland.

"It will reassure the public to know the investigation has been thorough and complete."

However, she said, we must "learn to live" with bacteria and viruses, which is why the agency has continued to urge people to maintain good hand hygiene, particularly when using the toilet or handling animals or food.

"No closer to finding out cause"

AMONG the victims of the infection who developed HUS and faced a fight for life was Isaac Mortlock, now four. He developed epilepsy as a result and has ongoing health problems.

"We are no closer to finding out what the cause of this outbreak is," said his mother, Gabrielle Archer, 27, whose Jessica also contracted HUS and was gravely ill.

"What happened to Isaac can still happen to other people. It looks like he will need a kidney transplant in the next few years, and he still has behavioural problems, seizures and hypos.

"My daughter Isabella is currently going through chemotherapy and I hate to think what would happen if she contracted E coli. It is very frustrating."

The family have previously expressed the belief that Isaac contracted the E coli infection through eating at a Bournemouth restaurant, although this venue has been ruled out as a cause through the Public Health England investigation.