Comparison of the airborne survival of calf rotavirus and poliovirus type 1 (Sabin) aerosolized as a mixture

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Abstract
A mixture of a cell culture-adapted strain (C-486) of calf rotavirus and poliovirus type 1 (Sabin) was prepared in tryptose phosphate broth containing 0.1% uranine (physical tracer) and antifoam at a final concentration of 0.001%. By using a 6-jet Collison nebulizer, the mixture was aerosolized into a 300-l stainless-steel rotating (4 rpm) drum. The temperature of the air inside the drum was kept at 20 .+-. 1.degree. C and the virus aerosols were held at the following 3 levels of relative humidity (RH): low (30 .+-. 5%), medium (50 .+-. 5%) and high (80 .+-. 5%). An all-glass impinger, containing 10.0 ml of tryptose phosphate broth with antifoam, was used to collect samples of air from the drum. Both viruses were propagated and quantitated in MA-104 cells. The calf rotavirus survived well at mid-range RH, where 60% of the infectious virus could be detected even after 24 h of virus aerosolization. At the low RH, the half-life of the infectious rotavirus was .apprx. 14 h. No infectious poliovirus could be recovered from the drum air at the low and medium RH. At the high RH, > 50% of the infectious rotavirus became undetectable within 90 min of aerosolization. In contrast to this, the half-life of the poliovirus at the high RH was about 10 h. These data, based on the aerosolization of virus mixtures, suggest that there is a pronounced difference in the way RH influences the airborne survival of these 2 types of viruses held under identical experimental conditions.