Around 70 people at a Royal Navy training base have been struck down with norovirus.
Those affected by the vomiting bug at HMS Raleigh in Cornwall have been placed in quarantine following the outbreak.
Sailors do their initial naval training at the base before joining courses at HMS Collingwood in Fareham and HMS Sultan in Gosport.
A Royal Navy spokesman said: ‘[The virus] started about ten days ago. It peaked towards the end of last week at about 70 and numbers fell rapidly after that.
‘The control measures introduced include intense cleaning and isolating those with symptoms.’
Typical symptoms of the vomiting bug include the sudden onset vomiting and diarrhoea.
There is no treatment for the virus.
Most people will recover within a few days.
The virus is spread through contact with an infected person or with contaminated surfaces or objects, or by consuming contaminated food or water.
It spreads particularly quickly in closed environments such as hospitals, schools and care homes, and can result in closures of classrooms and wards.