Russia is confronting one of its most serious public health threats since the collapse of the Soviet Union. The threat is tuberculosis, but with a dangerous twist: Strains of the bacteria are widely circulating that are resistant to ordinary anti-TB drugs, and far harder to cure.

Igor Davydenko is rail-thin with dark circles under his eyes. He has a haunted look, reinforced by black prison overalls with reflective tape on the shoulders and cuffs.