LONDON, ONT. -- CTV News has learned that seven employees at the London Transit Commission (LTC) are currently positive for COVID-19.

The union says bus drivers are now expressing fear about possibly contracting the illness while providing the essential service.

While ridership continues to lag well below average, London Transit remains an economic and mobility lifeline for tens of thousands of people.

But since late last week seven positive tests for COVID-19 have been reported by LTC employees.

LTC General Manager Kelly Paleczny tells CTV News that so far service hasn’t been impacted.

"Based on the number of staff right now, we're able to maintain service levels. Obviously that's something we're going to continue to monitor."

The LTC has 615 employees and the current cases have been within several departments -- including drivers.

The Amalgamated Transit Union (ATU) says the sudden rise in case counts has drivers on edge.

ATU Local 741 President Michael Gauthier says, "The riders don't have to wear their masks, although they say they do, they don't and this also creates a heightened sense of fear" for drivers.

Plexiglas barriers were installed in the summer to separate drivers from passengers, but that COVID-19 safety measure will be enhanced this Wednesday, Paleczny says.

"We were not requiring our operators to wear masks while behind a fully enclosed barrier, but starting tomorrow morning we are now asking that they wear masks at all times."

But the union says two things would help ensure there are enough drivers to keep bus service operating at its current level -- all passengers wearing masks and prioritization for the COVID-19 vaccine.

"Keep them healthy, and you know, potentially keep the service going without an issue. But yes if I do start losing more drivers I guarantee it's going to affect the service," Gauthier says.

Paleczny says the LTC has been in ongoing contact with the Middlesex London Health Unit throughout the pandemic.