Survival of variola virus in chorioallantoic membrane preparations.

The transmission of smallpox by contaminated bed clothes (Stallybrass, 1931) and by dust from the floor of a patient's room (Downie and Dumbell, 1947) is evidence of the stability of variola virus under natural conditions. Experimental proof of the survival of variola virus in exudates and crusts from humans was reported by Buddingh (1938) and North et al., (1944). The former investigator noted that vesicle fluid from a smallpox case was infective after 5 weeks at 0 C, and North et al. (1944) recovered virus from smallpox crusts which had been stored for 1 year at -8 C. Downie and Dumbell (1947) recorded the survival of variola virus in crusts kept at room temperature (18 to 20 C) for several months and in one specimen for over a year. As already noted, many of these observations were made at irregular or limited intervals and with the virus in either vesicular fluid or in dried crusts. Because of the variable composition of these materials, it was desirable to study the survival of variola virus in a standard preparation under definitive conditions. This report describes a quantitative study of the survival of variola virus in liquid and dried preparations of chorioallantoic membrane stored for extended periods of time at different temperatures.