The existence, probability and control measures of airborne infections
have been widely discussed for centuries. Although public belief regarding
airborne infection kept on altering throughout the entire history of medicine
and is still controversial, many airborne transmission experiments and airborne
infection outbreak analyses have been carried out. Different airborne
transmission models have been built and various airborne control measures
have been evaluated. One of the major knowledge gaps obstructing
applications of some airborne control measures in clinical practices and public
applications is that there is a lack of evidence in proving the effectiveness of
such measures.
Ventilation as an important airborne infection control method can be
achieved by opening windows, or increasing the outdoor air supply rate in
mechanical ventilation systems or indirectly by using filters and ultraviolet
equipments. However the applications of ventilation in infection control were
largely restricted to isolation rooms rather than regarded as a public control
measure. In this study we focus on evaluating the effectiveness of ventilation
as a community measure. Results, therefore, can provide evidence for using
ventilation as a public health measure for controlling respiratory diseases
transmitted by the airborne route or multi-routes.
Two mathematical modeling approaches (deterministic model and social
network model) are adopted to estimate different airborne diseases outbreaks
with a focus on ventilation and a corresponding analysis of their relative
effectiveness compared with other public health measures. A comprehensive
understanding of detailed control strategies (including both engineering and
public health control) will be achieved through gradually complicated and
realistic models.
It’s commonly believed that many respiratory infections are transmitted
through multiple routes including airborne, droplet-borne and contact routes.
Hence the effectiveness of airborne control measures was doubted when the
airborne route was not dominant. Therefore, we developed a model to simulate
partially airborne transmitted diseases outbreaks and evaluated the relative
effectiveness of ventilation when the role of airborne transmission altered.
Knowing the complex transmission mechanisms of respiratory
transmission and the role of the airborne route in the transmission process is
essential in determining the effectiveness of airborne control measures. Hence
in this study we also tested the virus exposures dose to infectious patients at
different distances when patients were carrying out different respiratory
activities. A complex model considering transmission mechanisms of
respiratory infections was also built to evaluate the influence of the
transmission route in large scale outbreak simulations.
The results showed that increasing ventilation rate especially in homes,
offices and classrooms is an effective control method for controlling airborne
and partially airborne transmitted infections. Combining isolation and
increasing ventilation rate can reach similar or even better control effect
compared with other general public health interventions such as vaccination.
This finding suggested the important role of ventilation in airborne infectious
disease prevention and intervention. The ventilation rate required by existing
ventilation standards such as ASHRAE 62 might be too low for the purpose of
controlling possible airborne outbreaks. / published_or_final_version / Mechanical Engineering / Doctoral / Doctor of Philosophy
| Identifer | oai:union.ndltd.org:HKU/oai:hub.hku.hk:10722/174458 |
| Date | January 2011 |
| Creators | Gao, Xiaolei., 高晓磊. |
| Contributors | Li, Y, Cowling, BJ, Leung, GM |
| Publisher | The University of Hong Kong (Pokfulam, Hong Kong) |
| Source Sets | Hong Kong University Theses |
| Language | English |
| Detected Language | English |
| Type | PG_Thesis |
| Source | http://hub.hku.hk/bib/B47752786 |
| Rights | The author retains all proprietary rights, (such as patent rights) and the right to use in future works., Creative Commons: Attribution 3.0 Hong Kong License |
| Relation | HKU Theses Online (HKUTO) |
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