A secondary school in Cheshire has been shut to deep clean the building after high levels of pupil sickness.
Congleton High School told parents and staff it contacted the UK Health Security Agency and infection control experts due to a "number of flu-like cases".
A letter said the school would be shut for two days from Wednesday while the deep clean takes place.
It said parents would get an update on Thursday to confirm whether school will reopen on Friday.
The UKHSA's Health Protection Team advised that pupils or staff who are vulnerable or immunosuppressed should seek health advice, and state that they "may have been exposed to influenza or another respiratory infection".
The letter said: "As we are currently unable to open, we have implemented a plan for the effective continuation of learning.
"Work will be set in accordance with the usual timetable, where staff are well enough to do so.
"A range of learning activities will be set... any additional teacher support in lessons will take place via Teams message or school email."
The school said students were expected to engage in remote learning on both days if they are well enough to do so.
Staff would be carrying out "safe and well checks" as appropriate, it added.
Congleton High School said it made the decision to close on Wednesday and Thursday due to a number of cases of flu-like illness in the school this week and following discussions with the UKHSA's Health Protection Team and Infection Control Team.
Cheshire East Council said it was liaising with the school to understand the impact on staffing, but at this stage most absences related to pupils.
Contingency plans were in place to maintain safe staffing levels, it stated.
"We know this is a worrying time for parents, but flu and similar illnesses are common during the winter months," said professor Rod Thomson, director of population health at the authority.
Vaccination was the most effective way to protect children and the wider community, said the professor, adding that if your child was unwell, to please keep them at home and follow NHS guidance.