E. coli case in child at Anglesey nursery
Testing is being offered to youngsters at an Anglesey nursery after a case of E. coli O157 was confirmed in a child.
The child fell ill last week but is said to be recovering well at home.
Three other children who attend the nursery, which has not been named, and two adults linked to it have also been unwell, said health officials.
Nobody has been taken to hospital. Children and staff at the nursery, which closed as a precaution, will be tested for E. coli O157.
Dr Chris Whiteside, of Public Health Wales, said: "E. coli O157 can have severe consequences for small children and, as the illness can spread easily in nurseries and schools, it is important that all children attending the nursery are tested.
"No children or staff will be allowed to attend the nursery until they have received two negative tests for E. coli O157 taken at least 48 hours apart."
Those classed as being in "at-risk" groups who are close contacts of people who are unwell will also be tested.
"People can become infected with E. coli O157 by eating contaminated food, or through contact with infected people, farm animals or contaminated water," said Dr Whiteside.
"The infection can also pass from person to person, so it is important that anyone who is ill should observe strict personal hygiene to avoid spreading the infection."
Symptoms include mild and bloody diarrhoea, stomach cramps and fever.
The incubation period can range from one to 14 days, but is usually three to four days.