What is cryptosporidium?
According to the NHS website, cryptosporidium is "a parasite found in soil, food and water that has been contaminated with animal or human faeces".
The BBC notes that "millions of parasites can be released in a single bowel movement which are then passed on to others through accidental ingestion".
It can cause an illness called cryptosporidiosis, also known as crypto. Symptoms, which usually appear between two and 10 days after being infected, include: diarrhoea, loose or watery stool, stomach cramps, upset stomach and fever.
Who is at risk?
Crypto can affect everyone but children or adults with a distinctly impaired immune system are at an elevated risk and could suffer more severely over a longer period.
How can I minimise the risk?
In practical terms, this means washing hands with soap and water after using or cleaning the toilet, changing nappies, clearing up after pets, gardening and before preparing food and drink and leaving the house.
Where has it been discovered in the UK?
Affected areas in the country include Blackpool, Chorley, Fylde, Preston, South Ribble and Wyre.
The bug was detected during routine tests at Franklaw water treatment outside Preston on Thursday (6 August).
More than 300,000 households have been warned by United Utilities to boil drinking water as an investigation into how cryptosporidium found its way into the system continues.
How long will I have to drink boiled water?
At present no definitive date has been set as to when residents can resume drinking tap water. According to a statement on United Utilities' website, all customers are being advised to "boil their water for all drinking, food preparation and brushing teeth as a precaution until further notice".
Boiled water is not required for general domestic purposes, such as bathing, flushing toilets and washing clothes.
A report by Sky states that residents will have to consume boiled water "until at least Monday or Tuesday".
Will United Utilities compensate me for the bottled water I have purchased?
In an FAQ section on its website, United Utilities says: "The advice we are giving is that your water can be used after you have boiled it."
Will United Utilities pay compensation?
United Utilities says: "Our focus is on returning water supplies to normal as quickly as possible. We will look into compensation once everything is back to normal."