Staff and almost 200 families at Sydney’s Liverpool Hospital are being screened for tuberculosis after a hospital health worker was diagnosed with the potentially fatal disease.

The hospital, in the city’s south-west, has revealed a worker in the maternity and neonatal units may have exposed 140 colleagues, 187 families and nine babies to the disease between December last year and March 6.

The NSW health department said the health worker is no longer at work and is receiving treatment and has advised there is no ongoing risk to patients and staff at the hospital.

The hospital has begun contacting parents of babies born in its maternity unit and cared for in the Neonatal Intensive Care Unit (NICU).

Tuberculosis screening and preventative medication will be available for all babies in the NICU and delivery suite who may have been in contact with the health care worker during the infectious period while screening and counselling will also be offered to parents.

Health care workers who worked in the NICU and birthing units during the period of exposure will also be screened.

Liverpool Hospital Chest Clinic Professor Guy Marks said the risk of a baby being infected with tuberculosis was low but it was still important that precautionary measures were taken.

"Tuberculosis is a common disease world-wide but across Australia approximately 1200 cases are diagnosed each year," he said. "It is relatively uncommon here."

Professor Marks said tuberculosis affected the lungs.

"Typically, it is spread through the air by people who have active tuberculosis, coughing.

"Fortunately, treatment for tuberculosis is highly effective."

Hospital clinicians are speaking directly with affected parents to discuss treatment options, answer questions and to arrange testing and assessment with neonatal and paediatric services.

Ahotline has also been established - phone 1800 059 647.