ST. LOUIS — The spread of COVID-19 is still real, and it has now silenced the St. Louis Symphony Orchestra (SLSO).

The works of composer Gustave Mahler were to be performed at Powell Hall this weekend, but the SLSO has canceled its concerts for Friday and Saturday due to multiple COVID breakthrough cases among orchestra musicians. It’s unclear how many musicians have tested positive.

Ticket holders can request an exchange, donate the value of their tickets to the SLSO, or request a refund by contacting the orchestra. The performances were scheduled for May 6 at 7:30 p.m. and May 7 at 8:00 p.m.

Currently, no make-up date has been announced.

The concerts were to feature Mahler’s First Symphony and Max Burch’s First Violin Concerto, plus the In-Unison chorus members.

The SLSO no longer requires proof of COVID-19 vaccination or negative test for audiences attending concerts and events at Powell Hall. Masks are recommended but not required.

The SLSO put the following message on its website Friday morning:

“The health and well-being of our audience members, musicians, staff, and community is our highest priority. Due to positive breakthrough COVID-19 cases in the orchestra, the SLSO has made the difficult decision to cancel this weekend’s concerts, May 6-7.”

Next weekend’s St. Louis Symphony Orchestra concerts for “Star Wars: Return of the Jedi” are still scheduled. The SLSO will also perform John William’s Oscar-winning score live with the film.