Persistence analysis of poliovirus on three different types of fomites.

AIMS: The goal of this study was to explore various models for describing viral persistence (infectivity) on fomites and identify the best fit models. METHODS AND RESULTS: The persistence of poliovirus over time was studied on three different fomite materials: steel, cotton and plastic. Known concentrations of poliovirus type 1 were applied to the surface coupons in an indoor environment for various lengths of time. Viruses were recovered from the surfaces by vortexing in phosphate buffer. Seven different mathematical models of relative persistence over time were fit to the data, and the preferred model for each surface was selected based on the Bayesian information criterion. CONCLUSIONS: While the preferred model varied by fomite type, the virus showed a rapid initial decay on all of the fomite types, followed by a transition to a more gradual decay after about 4-8 days. Estimates of the time for 99% reduction ranged from 81 h for plastic to 143 h for cotton. A 6 log reduction of recoverable infectivity of poliovirus did not occur during the 3-week duration of the experiment for any of the fomites. SIGNIFICANCE AND IMPACT OF THE STUDY: In protected indoor environments poliovirus can remain infective for weeks. The models identified by this study can be used in risk assessments to identify appropriate strategies for managing this risk.

Dose-response model for Burkholderia pseudomallei (melioidosis).

AIMS: The objective of this study was development of a dose-response model for exposure to Burkholderia pseudomallei in different animal hosts and analysis of the results. The data sets with which the model was developed were taken from the open literature. METHODS AND RESULTS: All data sets were initially tested for a trend between dose and outcome using the Cochran-Armitage test. Only data showing a statistically significant trend were subjected to further analysis (fitting with parametric dose-response relationships). Dose-response relationships (exponential, beta-Poisson and log-probit) were fit to data using the method of maximum likelihood estimation. CONCLUSIONS: Dose-response analysis of BALB/c mice, C57BL/6 mice, guinea pigs and diabetic rats showed that BALB/c mice exposed intranasally (i.n.) and guinea pigs exposed intraperitoneally (i.p.) are significantly more sensitive to B. pseudomallei than C57BL/6 mice exposed i.n. and diabetic rats exposed i.p. SIGNIFICANCE AND IMPACT OF THE STUDY: The results confirmed the findings of a study of outbreak data that the diabetic population is more susceptible to infection with B. pseudomallei than the general population. The low dose prediction from best fit dose-response models can be used to draw guidelines for public health decision making processes, including consideration of sensitive subpopulations.