With medics and helpers covered in masks, medical glasses and protective suits, it is sometimes hard to convey festive cheer to the patients in Moscow's Covid-19 wards.

But Leonid Krasner, who has been volunteering at a hospital since the first wave of the Covid-19 pandemic, has found a way with the colourful pictures he draws on the back of his overalls to help patients recognise him and bring a smile to those being treated.

Krasner, 59, decorates his single-use suits before entering the wards every time he is in the hospital. He once drew a cartoonish plane for a sick pilot and...