Risk assessment of infection transmission due to pathogen resuspension

Abstract

After the 2003 SARS outbreak which sent the world into the panic of an unknown virus that may spread through the aerosol pathogens. It is important to study on the transmission of pathogens through the airborne mode which may infect anyone who unknowingly inhaled the pathogens.

Studies had always focused on direct and basic aerosol transmission but there is a lack of studies on including the re-suspension mechanism which is another source of aerosol pathogen. In this project, re-suspension mechanism of pathogens is taken into account for the mass-balance model to calculate the concentration of pathogen in the air. Subsequently the concentration of pathogens in the air is inputted to the dose-response model to estimate the risk of infection.

The risk of infection is compared to the exposure time and ventilation rate in order to have a better recommendation of the required ventilation rate of a confine space. In this study we can see the significant effects of re-suspension towards the concentrations within the room and also the infection risk.

It is notice that for small quantity of pathogen emitted, in this case 3.993 micrograms per cubic metres per hour, the re-suspension factor could be omitted to simplify the calculations when results are being compared. However large amount of pathogens that are within the confine space would not be able to do so as it may give a skewed view on the overall risk assessment.

The minimal air change per hour value for isolation room recommended by World Health Organisation is found to be valid for small quantity of pathogens emission. It is notice that with a large amount of pathogens within the air, ventilation may deem to be helpless in reducing the risk of infection. The study notice that the risk of infection with 12 air change per hour will still yield a relatively high probability of infection of 0.79 in such situation.