Differences in Thermostability of Antigenically Related Strains of Poliomyelitis Virus.

Three rodent-adapted strains of poliomyelitis virus, all belonging to the same immunologic type, were found to differ in their thermostability; these were, in decreasing order of resistance, Y-SK, MEF1, and Lansing. The differences between these strains became evident only when they were suspended in cream or ice cream before being heated. All three strains suspended in water were inactivated by heating at 71.1 °C for 15 seconds. When heated in cream the viruses withstood 79.5°C for 15 seconds and in ice cream they withstood 82.2°C for 25 seconds, with Y-SK resisting inactivation to the greatest extent.