https://www.ctvnews.ca/world/russian-agent-dmitry-kovtun-accused-in-spy-poisoning-dead-at-57-1.5933082

Guess what? It was Covid.

Kovtun died Saturday of a COVID-19-induced illness. Russian news reports said he died at a hospital in Moscow.

A former agent for the KGB and its post-Soviet successor agency FSB, Litvinenko defected from Russia in 2000 and fled to London. He became involved in exposing corruption and links to organized crime in the Russian intelligence service.