Study On Quantitative Risk Assessment Of Human Infection From Legionella Aerosol In Public Building

Objective:To know the contamination level of Legionella pneumophila in public building and the Legionella pneumophila infection status in employee from public building and patients with pneumonia from general hospitals. To explore the environmental source of Legionella pneumophila infection. To construct the quantitative risk assessment method of human infection from Legionella aerosol which can be suitable for the contamination level and human exposure characterization of public building in China. It can establish the foundation for the early warning infection risk of microbial aerosol and provide groundwork for airborne disease prevention by contamination source management and transmission route control.Methods:The total of 77 public buildings were chose as study sites from Fengtai distinct of Beijing city, Nanjing city of Jiangsu province, Changzhou city of Jiangsu province and Shenzhen city of Guangdong province in 2009-2014. The cooling water, tap water, shower water, fountain water and soil, surface dust of HVAC system, soil nearby cooling tower, potting mix, aerosol samples of public buildings were collected from 4 areas of China from 2009 to 2014. The current contamination status of Legionella pneumophila was detected in environmental samples by nested PCR, while the contamination level of Legionella pneumophila was detected by real time PCR. The sputum, urine and serum samples were collected from 318 patients with pneumonia in general hospitals of four cities during 2012 to 2013. The urine and serum samples were collected from 280 emplyees in public building of four cities during 2013 to 2014. Legionella pneumophila in sputum was detected by nested-PCR. Legionella pneumophila antigen in urine and Legionella pneumophila antibody in serum were detected by ELISA. The sputum of patients with pneumonia in general hospitals and the environmental samples of public building was detected by nested PCR based on SBT and the products of PCR was sequenced. The nucleotide sequences similarities were analysed by phylogenetic analysis and molecular typing. The internal exposure level of Legionella pneumophila was assessed by monte corlo simulation based on the concentration Legionella pneumophila aerosol, exposure duration, and respiration rate. The expose infection relation was fitted by β-Poisson distribution and exponential function to assess the human infection risk. The risk assessment model was evaluated by factual data from field measurement and uncertainty of model will be analyzed.Results:The positive rate of Legionella pneumophila in the aerosol, cooling water, tap water, showering water, fountain water, soil nearby cooling tower, surface dust of HVAC, soil nearby fountain and potting mix of public building are 26.6%,81.4%,17.2%,36.4%,24.1%, 51.6%,33.8%,38.9% and 24.7% respectively. There was no significant in the positive rate of Legionella pneumophila in public buildings of different aeras(χ2=8.907,P=0.063). The positive rate of Legionella pneumophila in sputum, Legionella pneumophila antigen in urine and Legionella pneumophilaantibody in serum of patients with pneumonia in general hospitals were 11.8%,18.2% and 10.8% respectively. There were significant in the positive rate of Legionella pneumophila antibody in serum among the different aeras (χ2=14.306, P=0.002). The positive rate of Legionella pneumophila antigen in urine and Legionella pneumophila antibody in serum of emplyees in public building were 10.4% and 36.1% respectively. The positive rate of Legionella pneumophila antigen in urine of emplyees from shopping (13.5%) is higher than from hotel (5.5%). The haplotype diversity of gene flaA, pilE, asd, mip, mompS, proA and neuAare 0.920,0.858,0.928,0.968,0.942,0.794 and 0.733. The nucleotide diversity of gene flaA, pilE, asd, mip, mompS, proA and neuA are 0.02815, 0.02209,0.09577,0.11520,0.18807,0.05427 and 0.01437. The overall mean distance of gene flaA, pilE, asd, mip, mompS, proA and neuA are 0.0290,0.0227,0.3998,0.3378, 0.5901,0.072 and 0.0147. The ST number of sputum are same with the cooling water and showering water. The mean and standard deviation of the internal exposure level in the probability density function is 8.57 and 6.87. The mean human Legionella pneumophila infection risk of emplees in public building were 0.34 based on β-Poisson distribution and exponential function and the standard deviation are 0.20.Conclusion:There is particle and legionella pneumophila contamination in indoor air of public building of same areas in China according to this study. The results showed strong correlations between the concentration of PM10 and PM2.5. The concentration of Legionella pneumophila decreases with increase of air velocity. Legionella pneumophila infection was found in employee in public building and patients with pneumonia in the general hospitals. The combination detection of Legionella pneumophila of urine antigen, serum antibody and sputum can decrease false negative rate in Legionella infection investigation. The stay of other public building is the risk factor of Legionella pneumophila infection. The environmental source of Legionella pneumophila aerosol may be showering water and potting mix and the infection source of human may be recreational water and showering water. The potting mix was not the major infection source of human although it was bigger source contribution of aerosol. The recreational water was the major infection source of human although it was not much more source contribution of aerosol. The disinfection of recreational water is an effective method to reduce the risk of infection. The quantitative risk assessment method of human infection from Legionella pneumophila aerosol is established based on β-Poisson distribution and exponential function which overestimate the infection risk.