Public Health Wales is encouraging parents to get their children screened for TB, although it says the risk of the infection spreading within the school is low.
Screening for tuberculosis will today be offered to pupils at Ysgol y Strade school in Llanelli.
The 124 pupils at the secondary school are those identified as having around eight hours of close contact with the member of staff.
Tests will also be offered to 21 members of staff identified as close contacts of the patient.
More top news
More than 2,300 child sex offences were recorded by Welsh police forces last year - an average of more than six a day.
Rhondda MP Chris Bryant says security measures at the Palace of Westminster should be reviewed following yesterday's terror attack.
It comes after volunteer beach cleaners found balloon litter on beaches had increased by 53.5% between 2015 and 2016.