An Integrated Model of Infection Risk in a Health‐Care Environment

Abstract

Certain respiratory tract infections can be transmitted by hand-to-mucous-membrane contact, inhalation, and/or direct respiratory droplet spray. In a room occupied by a patient with such a transmissible infection, pathogens present on textile and nontextile surfaces, and pathogens present in the air, provide sources of exposure for an attending health-care worker (HCW); in addition, close contact with the patient when the latter coughs allows for droplet spray exposure. We present an integrated model of pertinent source-environment-receptor pathways, and represent physical elements in these pathways as "states" in a discrete-time Markov chain model. We estimate the rates of transfer at various steps in the pathways, and their relationship to the probability that a pathogen in one state has moved to another state by the end of a specified time interval. Given initial pathogen loads on textile and nontextile surfaces and in room air, we use the model to estimate the expected pathogen dose to a HCW's mucous membranes and respiratory tract. In turn, using a nonthreshold infectious dose model, we relate the expected dose to infection risk. The system is illustrated with a hypothetical but plausible scenario involving a viral pathogen emitted via coughing. We also use the model to show that a biocidal finish on textile surfaces has the potential to substantially reduce infection risk via the hand-to-mucous-membrane exposure pathway.

Virus shedding and environmental deposition of novel A (H1N1) pandemic influenza virus: interim findings

“…42 Detecting the presence of influenza in the air is the first step in a chain of evidence needed to confirm that influenza viruses -emitted from an infected individual and existing as bioaerosols -can initiate infection in a person exposed to them. The other steps in this sequence are (1) confirming that live, i.e.…”

Transfer Efficiency of Bacteria and Viruses from Porous and Nonporous Fomites to Fingers under Different Relative Humidity Conditions

“…The goal of this study was to obtain detailed quantitative information on fomite-to-finger transfer that could be used to model the probability of infection from exposure to various types of pathogens, a parameter needed for quantitative microbial risk assessments (1,5,48,49). Unfortunately, there are no standard methods for quantifying transfer rates, making it difficult to compare the results from various studies.…”

“…This information can be used to understand the spread of disease in indoor environments and the potential for designing surfaces that reduce transfer efficiency and/or are antimicrobial (5). The purpose of this work was to better elucidate the transfer efficiencies of several different types of organisms under control conditions to provide data that may be used in quantitative microbial risk assessment (QMRA) models.…”

“…nanimate objects, or fomites, are a potential reservoir in the transmission of pathogens either directly, by surface-to-mouth contact, or indirectly, by contamination of fingers and subsequent hand-to-mouth, hand-to-eye, or hand-to-nose contact (1)(2)(3)(4)(5). Bodily fluids such as saliva, mucus, nasal secretions, blood, urine, and feces may all potentially contain pathogens that can be transmitted via fomites (6)(7)(8)(9).…”

Exploring Antarctic subglacial lakes with scientific probes: a formal probabilistic approach for operational risk management

“…While such frameworks have been used in other domains (e.g. in infection control by Nicas and Sun, 2006), there is a dearth of peer-reviewed literature on the reliability of instruments and methods in glaciology. The focus has been on the reliability of scientific measurements, for example the reliability of ice-coring analysis (Alley, 2010).…”