None of the children or staff at a PAP Community Foundation Sparkletots pre-school in Clementi has been found to have active tuberculosis (TB), after the latest round of screening tests conducted by the authorities.

However, 39 children and four staff members were diagnosed with latent TB - which is not contagious - and are now being treated at the Tuberculosis Control Unit (TBCU).

The Ministry of Health (MOH) was following up after a staff member at the pre-school in Clementi Avenue 1 was diagnosed with active TB on March 3.

The affected person was immediately put on medical leave and started on treatment. On the same day, the TBCU contacted the school to identify people to be screened for the infection.

About 66 children and staff went for a first round of screening on March 14. Those who tested negative were screened again on May 9.

An expanded pool of 83 children was identified as close contacts of the affected person, with 79 having completed screening.

One is pending evaluation, while the parents of three children declined screening. Reasons behind their refusal are not known.

Tuberculosis is an airborne bacterial infection that is spread through close and prolonged contact with a person with the active form of the disease. Those with latent TB have no symptoms, do not feel sick and cannot spread the disease to others.

About 90 per cent of people with latent TB will never develop the active form, and treatment further reduces this risk, said an MOH spokesman.

The disease cannot be spread by sharing objects like utensils or food.

The 43 people who tested positive for latent TB in the Sparkletots case have been started on preventive treatment, which consists of up to nine months of daily medication,

Some parents said they appreciated the handling of the issue by MOH and TBCU, but felt the school could have done more in giving updates. A parent who wanted to be known only as Madam Hee, 36, whose three-year-old son was diagnosed with latent TB, said: "The school notified us about the staff member having TB on March 12, which was over a week after they found out on March 3."

Others echoed these sentiments.

Another parent, who gave her name only as Ms Lim and whose three-year-old boy also tested positive for latent TB, said: "I am disappointed because this is not the first time (this has happened in pre-schools), and we have yet to receive any statement or information from the pre-school."