Christopher Vourlias Three years after his musical drama “Leto” bowed on the Croisette, Kirill Serebrennikov returns to Cannes’ main competition with “Petrov’s Flu,” a deadpan, hallucinatory romp through a post-Soviet Russia in the grips of a mysterious flu epidemic. The acclaimed director spoke to Variety about living with fear and making the most out of solitude.How did you get involved with “Petrov’s Flu”? I was hired to write the script.