Residents in Newtown are being urged to take precautions to help ensure cases fall before the winter flu spike.
The jump in cases has also affected the county's contact tracing team which has been stretched by the volume of cases.
"Parents and guardians are being urged that if a child has a high temperature, a new continuous cough, or a loss or change to their sense of smell or taste, they ensure that they isolate immediately and get a PCR test," said a Powys County Council statement.
"In addition, twice weekly LFD testing is strongly encouraged for all secondary school age learners to help identify and isolate asymptomatic cases as soon as possible.
"The huge increase in case numbers is also having an impact on the county’s dedicated contact tracing team which is being stretched by the volume of cases. It has asked residents to be patient warning that calls may be delayed but that the team is working hard to reach contacts."