Parents in Wales have been warned to stay alert after E.coli closed another school and a nursery.
St David's Church in Wales primary school will reopen on Tuesday
A girl of six at St David's Church in Wales primary in Colwinston, Vale of Glamorgan, has contracted the bug.
The school will reopen on Tuesday after officials said there was no evidence it was linked to the earlier cases.
The Puffins nursery in Brecon was shut over the weekend. Since the outbreak began six weeks ago it has killed a boy of five and affected nearly 170 people.
Over 40 schools, mainly in the valleys, have been linked to the outbreak.
The new infections led public health officials to urge parents to continue to watch out for signs of ill health in their children.
Dr Tony Howard, of the outbreak control team, explained: "It's vital that we identify children who develop potential infection, and crucial that children who develop diarrhoea don't go to school and that children who develop bloodied diarrhoea, which has been a good marker of E.coli O157 infection in this outbreak, are brought to the attention of their doctors."
Officials are reviewing cleanliness measures to find out how the outbreak began, and a food hygiene leaflet will be sent to all schools in Wales.
Beth Thomas' daughter attends the Puffins nursery in Brecon
Dr Howard said: "This is an issue where people do need constant reminding."
The review leader, David Worthington, said: "There are systems out there that should have prevented this. If they are not, then clearly we have got a problem we need to address."
The St David's Church in Wales pupil is being treated at the Princess of Wales Hospital in Bridgend, and an investigation has been launched at both the 164-pupil Colwinston school and the Brecon nursery.
The first case at the Puffins nursery, which has 54 children, was identified on Wednesday, and more came to light over the weekend.
Public health officials took the decision to close the Brecon nursery while tests were carried out, and an intensive clean has been undertaken.
Parents of the pupils, who range from five to 10 months, have been contacted by environmental health officers.
One, Beth Thomas, whose baby daughter is at the nursery, said: "It's a frightening time. You heard all the cases around south Wales and you wouldn't think it's going to happen on your own doorstep."
Mason Jones, five, of Deri, died after contracting the E.coli infection
A private meeting for parents will take place at 1800 GMT on Monday at the Powys Council offices at Neuadd Brecheiniog in Brecon.
Families will be offered one-to-one advice and health officials will arrange for samples to be taken from the children.
Dr Marion Lyons from the Public Health Laboratory said: "Obviously if there is any risk in the nursery we will identify it now.
"We would encourage all parents in the community to be vigilant... hand washing and personal hygiene is very important," she added.
Health officials say it is likely that E.coli remains in the community due to the widespread nature of its original distribution.
The outbreak control team urged parents to keep vigilant and let their doctor know if their child has bloody diarrhoea.
The Welsh Assembly Government, which has promised a "no-holds-barred inquiry" into the outbreak, last week appointed food safety expert Professor Hugh Pennington as chairman.
Prof Pennington carried out an inquiry into an outbreak in Scotland in 1996 which killed 17 people.