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      In China, Students in Crowded Dormitories with a Low Ventilation Rate Have More Common Colds: Evidence for Airborne Transmission

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          Abstract

          Objective

          To test whether the incidence of common colds among college students in China is associated with ventilation rates and crowdedness in dormitories.

          Methods

          In Phase I of the study, a cross-sectional study, 3712 students living in 1569 dorm rooms in 13 buildings responded to a questionnaire about incidence and duration of common colds in the previous 12 months. In Phase II, air temperature, relative humidity and CO 2 concentration were measured for 24 hours in 238 dorm rooms in 13 buildings, during both summer and winter. Out-to indoor air flow rates at night were calculated based on measured CO 2 concentrations.

          Results

          In Phase I, 10% of college students reported an incidence of more than 6 common colds in the previous 12 months, and 15% reported that each infection usually lasted for more than 2 weeks. Students in 6-person dorm rooms were about 2 times as likely to have an incidence of common colds ≥6 times per year and a duration ≥2 weeks, compared to students in 3-person rooms. In Phase II, 90% of the measured dorm rooms had an out-to indoor air flow rate less than the Chinese standard of 8.3 L/s per person during the heating season. There was a dose-response relationship between out-to indoor air flow rate per person in dorm rooms and the proportion of occupants with annual common cold infections ≥6 times. A mean ventilation rate of 5 L/(s•person) in dorm buildings was associated with 5% of self reported common cold ≥6 times, compared to 35% at 1 L/(s•person).

          Conclusion

          Crowded dormitories with low out-to indoor airflow rates are associated with more respiratory infections among college students.

          Related collections

          Most cited references 32

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          Viruses and bacteria in the etiology of the common cold.

          Two hundred young adults with common colds were studied during a 10-month period. Virus culture, antigen detection, PCR, and serology with paired samples were used to identify the infection. Viral etiology was established for 138 of the 200 patients (69%). Rhinoviruses were detected in 105 patients, coronavirus OC43 or 229E infection was detected in 17, influenza A or B virus was detected in 12, and single infections with parainfluenza virus, respiratory syncytial virus, adenovirus, and enterovirus were found in 14 patients. Evidence for bacterial infection was found in seven patients. Four patients had a rise in antibodies against Chlamydia pneumoniae, one had a rise in antibodies against Haemophilus influenzae, one had a rise in antibodies against Streptococcus pneumoniae, and one had immunoglobulin M antibodies against Mycoplasma pneumoniae. The results show that although approximately 50% of episodes of the common cold were caused by rhinoviruses, the etiology can vary depending on the epidemiological situation with regard to circulating viruses. Bacterial infections were rare, supporting the concept that the common cold is almost exclusively a viral disease.
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            Aerosol transmission of rhinovirus colds.

            Rhinovirus infections may spread by aerosol, direct contact, or indirect contact involving environmental objects. We examined aerosol and indirect contact in transmission of rhinovirus type 16 colds between laboratory-infected men (donors) and susceptible men (recipients) who played cards together for 12 hr. In three experiments the infection rate of restrained recipients (10 [56%] of 18), who could not touch their faces and could only have been infected by aerosols, and that of unrestrained recipients (12[67%] of 18), who could have been infected by aerosol, by direct contact, or by indirect fomite contact, was not significantly different (chi 2 = 0.468, P = .494). In a fourth experiment, transmission via fomites heavily used for 12 hr by eight donors was the only possible route of spread, and no transmissions occurred among 12 recipients (P less than .001 by two-tailed Fisher's exact test). These results suggest that contrary to current opinion, rhinovirus transmission, at least in adults, occurs chiefly by the aerosol route.
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              Risk of indoor airborne infection transmission estimated from carbon dioxide concentration.

               S N Rudnick,  D Milton (2003)
              The Wells-Riley equation, which is used to model the risk of indoor airborne transmission of infectious diseases such as tuberculosis, is sometimes problematic because it assumes steady-state conditions and requires measurement of outdoor air supply rates, which are frequently difficult to measure and often vary with time. We derive an alternative equation that avoids these problems by determining the fraction of inhaled air that has been exhaled previously by someone in the building (rebreathed fraction) using CO2 concentration as a marker for exhaled-breath exposure. We also derive a non-steady-state version of the Wells-Riley equation which is especially useful in poorly ventilated environments when outdoor air supply rates can be assumed constant. Finally, we derive the relationship between the average number of secondary cases infected by each primary case in a building and exposure to exhaled breath and demonstrate that there is likely to be an achievable critical rebreathed fraction of indoor air below which airborne propagation of common respiratory infections and influenza will not occur.
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                Author and article information

                Contributors
                Role: Editor
                Journal
                PLoS One
                plos
                plosone
                PLoS ONE
                Public Library of Science (San Francisco, USA )
                1932-6203
                2011
                16 November 2011
                : 6
                : 11
                Affiliations
                [1 ]School of Environmental Science and Engineering, Tianjin University, Tianjin, China
                [2 ]Architecture Engineering Department, Pennsylvania State University, State College, Pennsylvania, United States of America
                [3 ]Tianjin Municipal Engineering Design and Research Institute, Tianjin, China
                [4 ]The Faculty of Urban Construction and Environmental Engineering, Chongqing University, Chongqing, China
                [5 ]School of Architecture, Tsinghua University, Beijing, China
                University of Liverpool, United Kingdom
                Author notes

                Conceived and designed the experiments: YS YZ JS. Performed the experiments: YS ZW. Analyzed the data: YS ZW JS. Contributed reagents/materials/analysis tools: YS YZ JS. Wrote the paper: YS JS. Contacted potential participants and communicated with the IRB committee: YS ZW YZ JS.

                Article
                PONE-D-11-02905
                10.1371/journal.pone.0027140
                3217956
                22110607
                Sun et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
                Page count
                Pages: 9
                Categories
                Research Article
                Biology
                Microbiology
                Virology
                Viral Transmission and Infection
                Population Biology
                Epidemiology
                Environmental Epidemiology
                Infectious Disease Epidemiology
                Engineering
                Environmental Engineering
                Medicine
                Epidemiology
                Infectious Disease Epidemiology
                Infectious Diseases
                Viral Diseases
                Common Cold
                Public Health
                Environmental Health
                Pulmonology
                Respiratory Infections
                Upper Respiratory Tract Infections
                Social and Behavioral Sciences
                Science Education
                Universities

                Uncategorized

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