The survival of filoviruses in liquids, on solid substrates and in a dynamic aerosol.

AIMS: Filoviruses are associated with high morbidity and lethality rates in humans, are capable of human-to-human transmission, via infected material such as blood, and are believed to have low infectious doses for humans. Filoviruses are able to infect via the respiratory route and are lethal at very low doses in experimental animal models, but there is minimal information on how well the filoviruses survive within aerosol particles. There is also little known about how well filoviruses survive in liquids or on solid surfaces which is important in management of patients or samples that have been exposed to filoviruses. METHODS AND RESULTS: Filoviruses were tested for their ability to survive in different liquids and on different solid substrates at different temperatures. The decay rates of filoviruses in a dynamic aerosol were also determined. CONCLUSIONS: Our study has shown that Lake Victoria marburgvirus (MARV) and Zaire ebolavirus (ZEBOV) can survive for long periods in different liquid media and can also be recovered from plastic and glass surfaces at low temperatures for over 3 weeks. The decay rates of ZEBOV and Reston ebolavirus (REBOV) plus MARV within a dynamic aerosol were calculated. ZEBOV and MARV had similar decay rates, whilst REBOV showed significantly better survival within an aerosol. SIGNIFICANCE AND IMPACT OF THE STUDY: Data on the survival of two ebolaviruses are presented for the first time. Extended data on the survival of MARV are presented. Data from this study extend the knowledge on the survival of filoviruses under different conditions and provide a basis with which to inform risk assessments and manage exposure to filoviruses.

Polysaccharides and virulence of Burkholderia pseudomallei.

Burkholderia pseudomallei is the causative agent of melioidosis, an infectious disease of humans and animals. Gene clusters which encode capsular polysaccharide (type I O-PS) and LPS (type II O-PS), both of which play roles in virulence, have previously been identified. Here, the identification of two further putative clusters, type III O-PS and type IV O-PS, is reported. Mice challenged with type III O-PS or type IV O-PS mutants showed increased mean times to death (7.8 and 11.6 days) compared to those challenged with wild-type B. pseudomallei (3 days). To investigate the possible roles of polysaccharides in protection, mice were immunized with killed cells of wild-type B. pseudomallei or killed cells of B. pseudomallei with mutations in the O antigen, capsular polysaccharide, type III O-PS or type IV O-PS gene clusters. Immunization with all polysaccharide mutant strains resulted in delayed time to death compared to the naïve controls, following challenge with wild-type B. pseudomallei strain K96243. However, immunization with killed polysaccharide mutant strains conferred different degrees of protection, demonstrating the immunological importance of the polysaccharide clusters on the surface of B. pseudomallei.

An alternative method of measuring aerosol survival using spiders' webs and its use for the filoviruses.

Understanding the ability to survive in an aerosol leads to better understanding of the hazard posed by pathogenic organisms and can inform decisions related to the control and management of disease outbreaks. This basic survival information is sometimes lacking for high priority select agents such as the filoviruses which cause severe disease with high case fatality rates and can be acquired through the aerosol route. Microthreads in the form of spiders' webs were used to capture aerosolised filoviruses, and the decay rates of Zaire ebolavirus and Marburgvirus were determined. Results were compared to data obtained using a Goldberg drum to measure survival as a dynamic aerosol. The two methods of obtaining aerostability information are compared.