Morrissey's double pneumonia is getting the best of him. The 53-year-old singer, who postponed a gig last Saturday (March 9) in San Francisco following the diagnosis, insisted he would be well enough to appear tonight (March 14) at the opening night of the Vive Latino Festival in Mexico City. But it turns out that's not the case, and Moz will be sitting this one out -- and, as a result, the entire opening day of the festival has been nixed.

"The Vive Latino Festival announces the cancellation of the opening day, Thursday, March 14, due to the health of British singer Morrissey," reads a post -- roughly translated -- that appeared on the Vive Latino website. "We apologize for any inconvenience this may cause to the public."

BlurYeah Yeah Yeahs and Underworld are among the other headliners still scheduled for Vive Latino, which runs through Sunday (March 17). Tickets to tonight's gig will be refunded starting Monday; details are available on the festival website. Morrissey's North American tour is scheduled to resume Monday in Lawrence, Kansas, and his San Francisco show has been rescheduled for May 2.