Effects of Temperature, Relative Humidity, Absolute Humidity, and Evaporation Potential on Survival of Airborne Gumboro Vaccine Virus

Survival of airborne virus influences the extent of disease transmission via air. How environmental factors affect viral survival is not fully understood. We investigated the survival of a vaccine strain of Gumboro virus which was aerosolized at three temperatures (10 degrees C, 20 degrees C, and 30 degrees C) and two relative humidities (RHs) (40% and 70%). The response of viral survival to four metrics (temperature, RH, absolute humidity [AH], and evaporation potential [EP]) was examined. The results show a biphasic viral survival at 10 degrees C and 20 degrees C, i.e., a rapid initial inactivation in a short period (2.3 min) during and after aerosolization, followed by a slow secondary inactivation during a 20-min period after aerosolization. The initial decays of aerosolized virus at 10 degrees C (1.68 to 3.03 ln % min(-1)) and 20 degrees C (3.05 to 3.62 ln % min(-1)) were significantly lower than those at 30 degrees C (5.67 to 5.96 ln % min(-1)). The secondary decays at 10 degrees C (0.03 to 0.09 ln % min(-1)) tended to be higher than those at 20 degrees C (-0.01 to 0.01 ln % min(-1)). The initial viral survival responded to temperature and RH and potentially to EP; the secondary viral survival responded to temperature and potentially to RH. In both phases, survival of the virus was not significantly affected by AH. These findings suggest that long-distance transmission of airborne virus is more likely to occur at 20 degrees C than at 10 degrees C or 30 degrees C and that current Gumboro vaccination by wet aerosolization in poultry industry is not very effective due to the fast initial decay.