Hunter New England Health is warning travellers to the Pacific Islands and Bali to take extra precautions when preparing or eating food after a rise in the number of cases of shigellosis.

Public Health Physician Dr David Durrheim said shigellosis is a bacterial gastroenteritis that can cause severe diarrhoea or dysentery.

"Shigella infection often follows eating of undercooked food or food that is inappropriately stored," Dr Durrheim said.

"Shigellosis spreads rapidly between people if hands are not properly washed after infected people have been to the toilet, particularly if they are involved in food preparation.

"It is apparent that holiday makers from the Pacific Islands and Bali are returning with shigellosis as a result of relaxed food and hand hygiene while visiting developing countries in the region," Dr Durrheim said.

The best way to minimise the spread of the disease is by washing your hands before food preparation, before eating, and after going to the toilet. Smokers should also minimise the spread of disease by washing their hands after smoking.

"Boil it, cook it, peel it or forget it’ is excellent advice for travellers to developing areas," Dr Durrheim said.

"These are good rules to follow to ensure that your holiday in the sun is not ruined by the infection."

Dr Durrheim said symptoms of shigellosis include diarrhoea, nausea, vomiting, stomach cramps and a fever.

"People returning from overseas with these symptoms should contact their GP for appropriate treatment, particularly if they have evidence of blood in the diarrhoea