CFD simulation of interflat air flow for the study of the spread of aerosol transmitted infectious diseases

In the world-wide scale outbreak of SARS in 2003, cluster of cases occurred in large building blocks, especially in Hong Kong. In this paper, we will examine one of the most likely virus-spread mechanisms, which is related to the inter-flat or inter-zonal air flow through open windows caused by buoyancy effects. Both tracer gas technique and CFD(computational fluid dynamics) techniques are employed to quantify the amount of the exhaust air coming out of the upper part of the window of a floor that re-enters the lower part of the open window at the immediate upper floor. The results can well explain the finding that DNA strings of SARS Corono-Virus(CoV) were detected within the sampled deposits on the window sills of the upper floors of the two index patients' flats. The preliminary and yet alarming conclusion may be that high-rise buildings with flush windows on the same vertical façade can be a major route for the vertical spread of pathogen-containing aerosols.