CHLORINATION OF HUMAN, MONKEY-ADAPTED AND MOUSE STRAINS OF POLIOMYELITIS VIRUS »•* BY

Although it is not yet possible to assess the epidemiological significance of the findings of the virus of poliomyelitis in sewage, it appears worth while to as-semble new data on the efficacy of chlor-ine as a viricidal agent.4 In 1931, Levaditi, Kling, and Lupine (1) reported that an initial dose of 0.4 ppm of chlorine after an extraordinarily long contact period of 24 hours destroyed a clear, filtered solution of poliomyelitis virus, and that 4.0 ppm were necessary to inactivate a turbid suspension of in-fected monkey cord. Using a very small number of monkeys, Kempf and Soule (2) found that a re-sidual chlorine concentration of 0.25 to 0.35 ppm (original concentration of 0.55 to 0.80) after 4-to-5 hour contact was required to destroy approximately one minimal infective dose (MID) of the MV strain. These investigators in a later re-port found that 1 to 1.5 ppm of residual Ch after 25-minute contact would inac-tivate approximately one MID of the MV strain (1 in 1,000 dilution of infected central nervous system tissue) and the DG strain (1 in 10,000 dilution) (3)