Abstract There have been few recent studies demonstrating a definitive association between the transmission of airborne infections and the ventilation of buildings. The severe acute respir...

It is essential to understand where and howsevere acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2)is transmitted.Case reports were extracted from the local Municipal Health Commissions of 320prefecturalmunicipalities in China (not including Hubei province). We identified alloutbreaks involving three or more cases and reviewed the major characteristics of the enclosed spaces in which the outbreakswere reported and their associated indoor environmental aspects.Three hundred and eighteen outbreaks with three or more cases were identified,comprising a total of 1245 confirmed cases in 120prefectural cities. Amongst the identified outbreaks, 53.8% involved three cases, 26.4%involved four cases, and only 1.6%involved ten or more cases. Home‐based outbreakswere the dominant category (254 of 318 outbreaks;79.9%), followed by transport‐based outbreaks (108;34.0%), and many outbreaks occurred in more than one categoryof venue. All identified outbreaksof three or more cases occurred in indoor environments, which confirmsthat sharing indoor spaceswith one or more infected persons isa major SARS‐CoV‐2 infection risk.

Severe acute respiratory syndrome (SARS) is primarily transmitted by bio-aerosol droplets or direct personal contacts. This paper presents a detailed study of environmental evidence of possible airborne transmission in a hospital ward during the largest nosocomial SARS outbreak in Hong Kong in March 2003. Retrospective on-site inspections and measurements of the ventilation design and air distribution system were carried out on July 17, 2003. Limited on-site measurements of bio-aerosol dispersion were also carried out on July 22. Computational fluid dynamics simulations were performed to analyze the bio-aerosol dispersion in the hospital ward. We attempted to predict the air distribution during the time of measurement in July 2003 and the time of exposure in March 2003. The predicted bio-aerosol concentration distribution in the ward seemed to agree fairly well with the spatial infection pattern of SARS cases. Possible improvement to air distribution in the hospital ward was also considered.

Effective ventilation in general hospital wards is important for controlling the airborne transmission of infectious respiratory diseases. Experiments have been carried out to increase our understanding of the interaction of the breathing flows of two individuals in a full-scale experimental hospital ward with three ventilation systems, i.e. mixing, downward and displacement ventilation. Two life-size breathing thermal manikins were used to simulate a source patient and a receiving patient. The exhalation jet from a bed-lying manikin was visualized using smoke. N2O was used as tracer gas to simulate the droplet nuclei exhaled by patients; and the spatial distribution of its concentrations was measured. Our experimental results show that for both mixing and downward ventilation, the exhaled jet penetrates a short distance and is diluted quickly by ventilation air. The exhaled droplet nuclei are well mixed in the ward. Bed distance does not affect the personal exposure of the receiving patient. For displacement ventilation, the exhaled jet can penetrate a long distance. A high concentration layer of exhaled droplet nuclei because of thermal stratification locking has also been observed with displacement ventilation. This work is useful for identifying an appropriate ventilation method that can remove droplet nuclei more effectively and minimize the risk of cross-infections in a hospital ward environment. As one of the major potential sources for infectious droplet nuclei in a hospital environment, exhalation flows of an infected patient can interact with the respiratory activities of other close individuals and with the room ventilation systems. Our latest results provide information on the penetration of exhalation jets into the ambient environment in different ventilation systems. This work is useful in identifying an appropriate and effective ventilation method for removing droplet nuclei more effectively, and thus minimizing the risk of cross-infections in hospital wards with multiple beds.

Asthma, rhinitis and eczema (allergic or non-allergic) have increased throughout the world during the last decades, especially among children. Changes in the indoor environment are suspected to be important causes. China has experienced a dramatic change in indoor environmental exposures during the past two decades. However, such changes and their associations with children’s asthma and other health aspects have not been thoroughly studied. China, Children, Homes, Health (CCHH), Phase I, was a cross-sectional questionnaire survey of 48219 children 1–8 years old in 10 Chinese cities during 2010–2012. The questionnaire includes the International Study of Asthma and Allergies in Childhood (ISAAC) core health questions and additional questions regarding housing, life habits and outdoor environment. In health analyses, children aged 3–6 years old were included. The prevalences of doctor diagnosed asthma varied from 1.7% to 9.8% (mean 6.8%), a large increase from 0.91% in 1999 and 1.50% in 2000. The prevalence of wheeze, rhinitis and atopic eczema (last 12 months) varied from 13.9% to 23.7%, 24.0% to 50.8% and 4.8% to 15.8%, respectively. Taiyuan had the lowest prevalences of all illnesses and Shanghai the highest, except for wheezewhere the highest value was for Urumqi. We found (1) no obvious association between disease prevalences and ambient PM₁₀ concentrations and (2) higher prevalences of disease in humid climates with hot summers and cold winters, but with no centrally heated buildings. Associations between the diseases and economic status as indexed by Gross Domestic Product (GDP) requires further study.