A guide for tackling an infectious vomiting bug on board cruise ships has been compiled by health experts.
Vomiting outbreaks have been reported on several ships
Norovirus causes sickness and diarrhoea and is easily transmitted in confined places, such as hospitals and schools.
But the bug has also struck thousands of people on cruises in recent years, prompting the Health Protection Agency to take action.
Its guide advises cruise ships to have a written "outbreak control plan" which should be followed if the bug strikes.
Details on cleaning areas with detergent, followed by disinfectant, are also outlined in the guide.
Before patients embark on their cruise, they should be given a precautionary letter outlining what to do if they feel unwell, together with a health questionnaire, it said.
According to the HPA, Norovirus can be difficult to control because it survives on surfaces and objects.
The infection usually lasts a couple of days, with symptoms including projectile vomiting, diarrhoea, high temperature, headaches and aching limbs.
There is no specific treatment for the bug, but patients are advised to drink plenty of fluids.
It infects between 600,000 and 1m people in the community in the UK every year.
HPA chief executive Professor Pat Troop said: "The aim was to produce straightforward and practical advice to discourage the introduction of infection to cruise ships in the first instance - and to help the industry and public health authorities manage outbreaks in a consistent manner when they do occur."
William Gibbons, director of the Passenger Shipping Association, said of the guide: "It means that all parties who are required to deal with an outbreak of infection will have immediate access to sound and practical advice that will minimise the impact for passengers and crew alike."