The Public Health Agency are contacting about 270 people who have been in contact with a health are worker who been diagnosed with tuberculosis (TB).
The individual concerned worked in the Southern Health Board area.
Most people contacted will receive information and over 40 will be offered TB screening as a precaution, in line with standard practice.
PHA Consultant, Dr Michael Devine, said the risk to patients was low as "TB is a difficult infection to catch".
"It is caused by a germ and most commonly affects the lungs," Dr Devine said.
"It is usually spread through the air when someone coughs or sneezes."
Although TB can be serious, it is easily treated with antibiotics. There are around 70 cases in NI each year and most patients make a full recovery.
A factsheet on TB is available on the website of the Health Protection Agency.