The Public Health Agency is warning people to be aware of an increase in levels of the Norovirus - more commonly known as stomach flu.
The agency has recommended simple steps to minimise the risk of the illness, especially among older people and those with underlying conditions.
It said hand hygiene is the simplest way to reduce the spread of infection, which causes vomiting and diarrhoea.
A number of cases have been reported in Northern Ireland hospitals.
The PHA's Dr Lorraine Doherty said the infection can spread quickly in close-knit communities such as nursing homes, schools, hospitals and workplaces.
"The illness can last as little as 12 hours or up to three days," she said.
"The only treatment is to stay at home, rest, take plenty of fluids, and to reduce contact with others, both in the home and at work.
"It is very important for people who have symptoms of illness not to visit hospitals or their GP surgery."