About 25 people at two Sunshine Coast hospitals are believed to have come down with the highly contagious norovirus gastroenteritis.
Queensland Health is trying to contain the outbreak, which has hit 18 patients at the Caloundra hospital and seven at the Nambour hospital.
Infection Control Staff Specialist Dr Keat Choong said on Tuesday staff had quarantined patients.
"We want to minimise the risk of an outbreak and protect vulnerable hospital patients from the adverse effects," Dr Choong said.
People who have vomiting or diarrhoea should avoid visiting hospital patients until 48 hours after their symptoms have disappeared.
The main symptoms are vomiting, diarrhoea, nausea, stomach cramps, fever and headaches.
