While most victims of the micro-organism suffer only sickness and diarrhoea, the consequences can be more serious for those with critical conditions. It was not until several days after Nikita's dash to hospital that Mrs Allen, of Abbotskerswell, Devon, learnt the bug was responsible. "I was furious," she said. "Because of the hot weather she was drinking glasses of squash with water from the tap. We pay so much money down here for water it should at least be drinkable. I'll always boil it in future."
Nikita seems fully recovered from her illness, but will see a specialist later this month to see if the strain has done any lasting damage to her heart.
The couple are now planning to sue South West Water with the aim of generating publicity and perhaps teaching the company a lesson. Nikita's father, Darren, said: "We'd like to give SWW a bloody nose. This is England, not the Third World. We should be able to take for granted decent drinking water."
The Allens' solicitor, Derek Reed, of solicitors Woollcombe Beer Watts in Newton Abbot, which is handling more than 40 complaints, said: "Most of the claims are from individuals and some of them are particularly nasty cases involving children where in-patient hospital treatment has been needed."