However, government health experts say it’s impossible to say whether the crisis caused the surge because there was also a national and international increase.
A spokesman for Public Health England said: “It is a likely conclusion that there were no cases directly attributable to the incident.”
Between June and September, there were 97 cases reported in Lancashire, up from 77 during the same period in 2014 and 49 in 2013.
People at 300,000 homes and businesses were forced to boil their water for 30 days after water supplied by the Franklaw water treatment plant, at Catterall near Garstang, was contaminated by the bug.
Families across the Fylde, Wyre, Preston, Leyland and Chorley, had to treat all water for drinking, food preparation and even cleaning teeth to avoid being hit by the stomach cramps, sickness, and diarrhoea that cryptosporidium can bring on.
“It is really difficult to give a definite answer on whether the incident resulted in an increased incidence of cases caused by this event,” Public Health England said in council documents set to go before Blackpool’s health and well-being board next Wednesday.
“Going through the questionnaires for all those within the ‘Boil Water Notice’ area, for the majority there were other risk factors so we couldn’t categorically say where they caught it.
“There was also a national increase in crypto at the time which didn’t help with surveillance.”
A spokeswoman added: “The cryptosporidium cases for the period of the boil water notice and several weeks beyond were looked at individually. The majority had other risk factors that could cause cryptosporidium, such as international travel, or contact with wild or farm animals.
“The rates of cryptosporidium in Lancashire during the period of the boil water notice were similar to other areas in the north west and followed national trends.
“Several other European countries also saw an increase in cases last summer.
“We concluded that there was no evidence of an outbreak as no direct cause presented itself throughout the investigation.”
The outbreak cost United Utilities £25m in compensation payments to bill-payers across the county.