https://www.sciencedirect.com/science/article/pii/S1877959X17302042

Paywalled, academic source: "It was 1937, a period of massive oppression in the Soviet Union. This occurred in the party ranks, in the army, among scientists, artists, workmen, and peasants. The leader of the first expedition, Professor Zilber, and two of his team members, A.D. Sheboldaeva and T.M. Safonova, were arrested after slanderous denunciation. Zilber and his colleagues were accused of spreading Japanese encephalitis virus under the guise of performing scientific research and of spreading the newly discovered and isolated dangerous virus among military contingents in the Far East and among the inhabitants of Moscow (Kisselev and Levina, 2005). However, the charges were so absurd and Zilber’s innocence was so evident that he was released in 1939. Perhaps, this release occurred because of the arrival of the new leader of repressive measures, Lawrenti Beria, who tried to disguise mass terror by releasing a small number of prisoners (see also Kisselev et al., 1992). It also needs mentioning that Zilber’s followers and his colleagues, as well as the famous writer V. Kaverin and the microbiologist and epidemiologist Zinaida Ermolyeva, who gave the USSR penicillin during World War II, campaigned vigorously for Zilber’s release."