Parents in England are being urged to keep children off school if they are unwell and have a fever, amid high levels of flu and Covid-19 cases.
The same applies for nurseries, according to advice from the UK Health Security Agency (UKHSA).
The number of scarlet fever cases is also high, it warned.
A head teachers' union welcomed the advice, issued as pupils prepare to return to lessons after the Christmas holidays.
Flu and Covid cases are "currently circulating at high levels and are likely to continue to increase in coming weeks", the UKHSA said.
"High numbers of scarlet fever, which is caused by group A streptococcus, also continue to be reported."
