The Cystovirus phi6 as a simulant for Venezuelan equine encephalitis virus

Innocuous organisms able to simulate the properties of pathogens are necessary so that the behaviour of pathogenic microorganisms in the environment may be understood. This is essential if we are to understand the epidemiology and consequence management of airborne infection, whether natural or the result of a deliberate release. The coliphage MS2 has been widely used as a simulant for mammalian viruses, although it bears little structural or biochemical similarity to the agents of interest. The well-characterised bacteriophage phi6 (host Pseudomonas syringae) is closer in size and complexity to pathogenic viruses, notably the Alphavirus Venezuelan equine encephalitis virus (VEEV) because the virion has surface structures and is bounded by a lipid envelope. Here, we show for phi6 that the assay is simple and precise and that the infectivity is stable in buffers and under conditions used for aerobiology experiments, it is retained after aerosolisation and sampling. Finally, phi6 aerosol was generated into a re-circulating wind tunnel where a stable and acceptable level of viability was maintained. Phi6 may prove a useful simulant for VEEV and possibly for other lipid-containing viruses as well.