Doctors from West Hertfordshire Health Authority say 85 people have severe diarrhoea after their water was infected with the micro-organism cryptosporidium.
And thousands more householders were yesterday told to boil their water after a separate outbreak caused another eight people in Bedfordshire to fall victim to the infection. French-owned Three Valleys Water issued the warning to 25,000 homes in Bedfordshire following an earlier alert on Sunday to 750,000 people in Hertfordshire and north-west London.
Three Valleys communication manager Frank Fitzpatrick said: "The two incidents are not linked. Bedfordshire is supplied by a reservoir, while the other areas are supplied by ground water sources.
"We are still unable to establish whether the outbreaks are a result of direct water contamination."
Dr Barry Tennison, director of health for West Hertfordshire, said people should continue to boil water for drinking, cooking and brushing teeth.
"There may be more cases in the next few days because there is a 7-10 day incubation period," he said. Doctors at Bedfordshire Health Authority said a boil notice should be issued after seeing an increase in the number of severe diarrhoea cases.
Cryptosporidium belongs to a group of protozoa occurring in the farm animal dung. It is normally spread through contaminated water or contact with an infected person. Unpasteurised milk and offal also carry risks.
If Independent inspectors from the Drinking Water Inspectorate find the company negligent, they might press for prosecution.Reuse content