The use of aerosolized bacteriophages as surrogates for hazardous viruses might simplify and accelerate the discovery of links between viral components and their persistence in the airborne state under diverse environmental conditions. In this study, four structurally distinct lytic phages, MS2 (single-stranded RNA [ssRNA]), 6 (double-stranded RNA [dsRNA]), X174 (singlestranded DNA [ssDNA]), and PR772 (double-stranded DNA [dsDNA]), were nebulized into a rotating chamber and exposed to various levels of relative humidity (RH) and temperature as well as to germicidal UV radiation. The aerosolized viral particles were allowed to remain airborne for up to 14 h before being sampled for analysis by plaque assays and quantitative PCRs. Phages 6 and MS2 were the most resistant at low levels of relative humidity, while X174 was more resistant at 80% RH. Phage 6 lost its infectivity immediately after exposure to 30°C and 80% RH. The infectivity of all tested phages rapidly declined as a function of the exposure time to UVC radiation, phage MS2 being the most resistant. Taken altogether, our data indicate that these aerosolized phages behave differently under various environmental conditions and highlight the necessity of carefully selecting viral simulants in bioaerosol studies. Human populations are constantly exposed to viral particles, whether through direct or indirect contacts with an infected individual or through contaminated environments. Despite precautions, we remain at risk of exposure to infective viral particles, particularly through the airborne route. This mode of transmission is difficult to control in our everyday lives due to the ubiquitous nature of airborne particles, which may harbor infectious materials. Although the airborne route is not the most effective mode of transmission for the majority of known human pathogens, many viruses may be transmitted through this route (1). For example, measles, varicella zoster (2), and variola (3) viruses are naturally transmitted by aerosols. Other viruses, such as Newcastle disease virus, are particularly resistant to aerosolization and may potentially cause infections by the aerosol route (4, 5). On the other hand, the importance of aerosol transmission in the spread of some viruses, such as the influenza virus, is still a subject of debate (6).Aerosolized particles may be involved in viral transmission at short range through contamination of fomites by the rapid deposition of large droplets. However, true aerosol dissemination implies that sufficiently small infectious particles remain airborne for a prolonged period (2). Particles smaller than 5 m in aerodynamic diameter have the potential to travel long distances, as they sediment more slowly. However, these smaller particles harbor fewer viruses than larger particles but also less material that might protect the viruses in the airborne state. Indeed, viral resistance to aerosolization is partly dependent upon the composition of the droplet or droplet nuclei (5,7,8). Furthermore, the resistance of viruses to...

A chamber was designed and built to study the long-term effects of environmental conditions on air-borne microorganisms. The system consists of a 55.5-L cylindrical chamber, which can rotate at variable speeds on its axis. The chamber is placed within an insulated temperature controlled enclosure which can be either cooled or heated with piezoelectric units. A germicidal light located at the chamber center irradiates at a 360° angle. Access ports are located on the stationary sections on both ends of the chamber. Relative humidity (RH) is controlled by passing the aerosol through meshed tubes surrounded by desiccant. Validation assay indicates that the interior temperature is stable with less than 0.5 °C in variation when set between 18 and 30 °C with the UV light having no effect of temperature during operation. RH levels set at 20%, 50% and 80% varied by 2.2%, 3.3% and 3.3%, respectively, over a 14-h period. The remaining fraction of particles after 18 h of suspension was 8.8% at 1 rotation per minute (rpm) and 2.6% at 0 rpm with the mass median aerodynamic diameter (MMAD) changing from 1.21 ± 0.04 μm to 1.30 ± 0.02 μm at 1 rpm and from 1.21 ± 0.04 μm to 0.91 ± 0.01 μm at 0 rpm within the same time period. This chamber can be used to increase the time of particle suspension in an aerosol cloud and control the temperature, RH and UV exposure; the design facilitates stationary sampling to be performed while the chamber is rotating.