Saints were due to train at Stirling University on Thursday morning but after fielding calls from ill players at the campus the Northern Irishman called off the session.
Lomas will have a roll call in the morning but any withdrawals at all is bound to have an effect on a side struggling at the bottom of the SPL table with two points from five games.
"We've had to cancel training this morning (Thursday) because there are six or seven players down with a bug," he told Press Association Sport.
"There's not much we can do about it, we will see how things are tonight and tomorrow."
- Stirling University