Health chiefs say they have not had a solitary case of cryptosporidium infection in Lancashire linked to the current water scare.
Despite the alert now being in its ninth day - past the most common time limit for the illness to show up - Public Health England insists any possible outbreak has so far not materialised.
“Since the incident we can confirm that we have not had any cases that we can directly link with the ongoing situation, nor have we seen a rise in the number of cases that we would normally see at this time of year,” said Dr John Astbury from the Cumbria and Lancashire Health Protection Team.
“The incubation period for cryptosporidium is between one and 12 days, but it usually averages about seven. We are now past the medium point since we have been notified and we have had no lab-confirmed cases as yet.”
More than 300,000 households are still being advised to boil water for drinking, food preparation and brushing teeth more than a week after the alarm was raised.
Dr Astbury added: “We are unable to talk about individual cases, however it is not unusual to see cases of cryptosporidium at any time within a community and on average PHE would see between 3,000 to 6,000 cases nationally.
“It is therefore difficult to ascertain whether a case that has occurred recently would be the result of the on-going situation or infection that would have occurred as a result of a different exposure to cryptosporidium.
“Further, as at any time of the year, there may be people suffering with symptoms of diarrhoea and vomiting – these symptoms are fairly common and can be the result of undercooked food, poor hand hygiene or other infections and will not necessarily be as a result of cryptosporidium.
“PHE is aware that this investigation has taken longer than anticipated, however residents should be reassured that the boiled water notice will be lifted as soon as it is safe to do so.
“We remind people in the affected areas to follow the advice from United Utilities and boil their drinking water and allow to cool before use. The levels of cryptosporidium detected in the water supply is low and the advice to boil the water is as a precaution.
“If anyone does have symptoms of diarrhoea and vomiting our advice is to stay hydrated, practice strict hand hygiene, stay away from work or other gatherings until 48 hours after the last bout of symptoms and if you are concerned phone your GP or NHS 111.”