Cryptosporidiosis is not a new illness, occurs in cycles, and is often associated with contact with animals during the spring lambing season. Health officials have said that a normal "peak" at the end of March came several weeks earlier this year in Galway city and county.
The condition spreads by accidentally swallowing anything that has come into contact with faeces, or by swallowing contaminated water in a swimming pool, jacuzzi, lake, river or pond. It can also be contracted through eating uncooked contaminated foods.
Boiling is recommended to ensure that water is free of cryptosporidium and other germs, and people unsure of the source of their water should also take the same measures, HSE West says. This applies to water used for drinking, drinks made with water, preparation of salads and similar foods which are not cooked before eating, brushing of teeth, ice-making.
Baby feeds should be prepared with water boiled and left to cool, and water should not be reboiled several times.
Bottled mineral water should not be used for baby food preparation.
The HSE West says that anyone suffering from diarrhoea for more than two days should contact their doctor and provide a stool sample for testing, and should drink plenty of boiled or bottled water.
A map of affected areas and further information is on websites www.galway.ie www.galwaycity.ie and www.hse.ie