咳嗽飞沫核携带病毒在病房机械通风条件下经空气传播的人工模拟技术研究

 目的 建立评估呼吸道传染病经空气传播能力的现场试验研究方法。方法 在典型机械通风病房内雾化含有大肠埃希菌噬菌体的模拟唾液，雾化液滴与咳嗽飞沫具有类似粒径分布的液滴谱系，检测空气中不同粒径液滴核数量并估算其初始液滴的几何尺寸，计算液滴核初始携带的噬菌体数量，通过采集空气生物标本获得液滴核内噬菌体的实际存活量，比较两组数据获得液滴核携带的噬菌体在病房空气中的存活函数。结果 在表面蒸发作用下，模拟唾液雾化液滴所携带的存活噬菌体数量快速损失约83%，在360 s的检测时间段内液滴核内的噬菌体平均存活函数稳定在17%且不随检测点变化，室内空气中液滴核数量的衰减率与空气生物标本中噬菌体数量的衰减率一致，记录雾化液滴核数量即可推算病房空间生物暴露水平。结论 咳嗽飞沫核携带病毒在空气中传播的人工模拟技术，可用于评估呼吸道传染病经空气传播能力的现场试验研究。     

中国公民健康素养66条

正肺结核主要通过病人咳嗽、打喷嚏、大声说话等产生的飞沫核传播;出现咳嗽、咳痰2周以上,或痰中带血,应及时检查是否得了肺结核。肺结核病是由结核分枝杆菌(结核菌)引起的呼吸道传染病。痰检有结核菌的病人有传染性,具有传染性的病人通过咳嗽、打喷嚏、大声说话产生的飞沫核(微小颗粒)传播结核菌。健康人吸入带有结核菌的飞沫核就会形成结核感染,感染结核菌的人如果抵抗力低或感染菌量大、毒力强就可能得结核病。     

结核病的防治对策与瞻望(续)

三、结核病在我国的流行情况(一) 结核病的流行环节结核病是由排菌的病人呼吸道尤其咳嗽或喷嚏时排出大量雾化带菌的飞沫核传染的。只有微小(1～10微米)的飞沫核才能进入易感者的肺泡或微小支气管末梢形成感染,较大的飞沫核即使吸入到呼吸道也为粘膜纤毛毡运动排到口咽被吞下或咳出,不致传染。结核菌不能侵入完整的皮肤或粘膜,据证明,病     

中国公民健康素养66条

正肺结核病是由结核分枝杆菌(结核菌)引起的呼吸道传染病。痰检有结核菌的病人有传染性,具有传染性的病人通过咳嗽、打喷嚏、大声说话产生的飞沫核(微小颗粒)传播结核菌。健康人吸入带有结核菌的飞沫核就会形成结核感染,感染结核菌的人如果抵抗力低或感染菌量大、毒力强就可能得结核病。一般连续2周以上咳嗽、咳痰,或痰中带血通常是肺结核的主要症状;如果对症治疗2     

楼内怪事

某单位一幢18层的住宅楼近日出现一件怪事,有人在夜深人静之时,在电梯内撒尿。电梯管理人员进一步观察到小便十人有规律,大约总是在夜里12点钟左右,在轿厢里用尿液沿轿壁浇一圈才罢休,一连两周如此,事情虽然够不上犯罪,但却较为恶劣。每天早上一大早,轿厢里便是一股浓浓的尿臊味儿,让人感觉乘电梯像是在厕所里似的,因为是单位的住宅楼,住在里面的居民都是一大早起来买早点,大家端着各种牛奶、豆浆、油条……进这尿臊味十足的电梯,     

换气勤空气除菌

据报道,一个人感染上结核菌,一般需要与传染源有1个月的以上的接触史,但若吸入高浓度飞沫核,仅接触2个小时就易染结核菌。一个有传染性的结核病人,每年在家庭、学校、工作场所或社区内可以传染10——20个人。 结核病可以发生爆发流行的事件,其中重要原因之一就是:患者工作生活环境通风条件不好。某地一计算所站职工李某因咳嗽,咳痰2月余,经查发现空洞形成,痰涂片阳性,仍在单位上班。单位是一个封闭的中央空调,室内很少补充新鲜空气,后陆续出现十几例病人。     

图说健康

正肺结核主要通过病人咳嗽、打喷嚏、大声说话等产生的飞沫传播为了预防结核病,儿童出生后应及时接种卡介苗。平时要经常锻炼身体,增强体质。工作、生活场所要注意通风。具有传染性的肺结核病人应当积极治疗,尽量少去公共场所,必须外出时应佩戴口罩。在咳嗽、打喷嚏时要用纸巾或手帕捂住口鼻。     

广州市部分医院电梯内微生物的污染

医院电梯空间狭小,人员拥挤,通风不良,按钮表面、电梯间空气易受各种微生物的污染.为了解医院电梯的污染情况,为医院内感染的预防提供可靠的依据,笔者于2004年12月11-14日,对广州市海珠区人流量不同的3家医院(三级甲等、二级甲等、普通)电梯内按钮与空气微生物污染进行监测.其中二级甲等医院有8部电梯,日人流量为3 000～5 000人次;二级甲等医院有2部电梯,日人流量为1 000～3 000人次;普通医院有1部电梯,日人流量为500～1 000人次.连续采样4 d.     

麻疹流行病学

１．传染源与传播途径麻疹病人是本病唯一的传染源。人和人之间主要通过大的呼吸飞沫传播，也可通过雾化飞沫核引起空气源性播散。含有病毒的分泌物通过病人的呼吸、咳嗽和喷嚏排出体外在空气中悬浮，易感者经呼吸道，也可伴眼结膜感染，由于麻疹病毒可以在空气中存在一定...     

我国结核病疫情特征与防治策略

1 结核病感染与传播风险 1.1 结核病感染、传播与发病过程 易感者与传染源密切接触的情形:接触时间;接触方式(密切、偶尔);密室接触、通风不良;卫生习惯不良. 结核病感染、传播与发病过程见图1. 1.2 结核病感染-潜伏感染与发病几率 人体暴露于有传染性肺结核患者的环境,吸入含有结核菌的痰液飞沫后,并不是所有的人都会被感染或发病,其感染与发病机率见图2. 1.3结核病感染3要素 结核病感染的3要素包括传染源、传播途径、易感者(见图3).传染源主要是传染性肺结核患者.含有大量结核菌的痰液,通过咳嗽、打喷嚏、大声说话等方式经鼻腔和口腔喷出体外,在空气中形成飞沫,小的飞沫长时间悬浮在空气中.含结核菌的飞沫被易感者吸入肺泡,就可能引起感染.     

Virus diffusion in isolation rooms

In hospitals, the ventilation of isolation rooms operating under closed-door conditions is vital if the spread of viruses and infection is to be contained. Engineering simulation, which employs computational fluid dynamics, provides a convenient means of investigating airflow behaviour in isolation rooms for various ventilation arrangements. A cough model was constructed to permit the numerical simulation of virus diffusion inside an isolation room for different ventilation system configurations. An analysis of the region of droplet fallout and the dilution time of virus diffusion of coughed gas in the isolation room was also performed for each ventilation arrangement. The numerical results presented in this paper indicate that the parallel-directional airflow pattern is the most effective means of controlling flows containing virus droplets. Additionally, staggering the positions of the supply vents at the door end of the room relative to the exhaust vents on the wall behind the bed head provides effective infection control and containment. These results suggest that this particular ventilation arrangement enhances the safety of staff when performing medical treatments within isolation rooms.     

BSL-3实验室通风方式及污染源位置对气溶胶颗粒分布的数值研究

目的：对BSL-3主实验室上送上排、上送下排2种通风方式的气流运动以及污染源位置对气溶胶颗粒浓度分布影响进行数值研究。方法：利用离散轨道模型模拟气溶胶颗粒的轨迹,并与模拟气流运动的标准湍流模型相耦合。结果：在主实验室送风量、压力以及污染源发射强度不变的情况下,不仅通风方式是影响气溶胶颗粒分布的因素,污染源发生位置也是影响室内颗粒浓度分布的重要因素。结论：对比6个方案,上送上排污染源在位置1时呼吸区有最小的浓度和更好的整体排污效率,上送下排污染源在位置3时呼吸区有最大的浓度和最差的整体排污效率。     

Reaerosolization of MS2 bacteriophage from an N95 filtering facepiece respirator by simulated coughing

The supply of N95 filtering facepiece respirators (FFRs) may not be adequate to match demand during a pandemic outbreak. One possible strategy to maintain supplies in healthcare settings is to extend FFR use for multiple patient encounters; however, contaminated FFRs may serve as a source for the airborne transmission of virus particles. In this study, reaerosolization of virus particles from contaminated FFRs was examined using bacteriophage MS2 as a surrogate for airborne pathogenic viruses. MS2 was applied to FFRs as droplets or droplet nuclei. A simulated cough (370 l min(-1) peak flow) provided reverse airflow through the contaminated FFR. The number and size of the reaerosolized particles were measured using gelatin filters and an Andersen Cascade Impactor (ACI). Two droplet nuclei challenges produced higher percentages of reaerosolized particles (0.21 and 0.08%) than a droplet challenge (<0.0001%). Overall, the ACI-determined size distribution of the reaerosolized particles was larger than the characterized loading virus aerosol. This study demonstrates that only a small percentage of viable MS2 viruses was reaerosolized from FFRs by reverse airflow under the conditions evaluated, suggesting that the risks of exposure due to reaerosolization associated with extended use can be considered negligible for most respiratory viruses. However, risk assessments should be updated as new viruses emerge and better workplace exposure data becomes available.     

FLUENT仿真计算在丝网印刷作业环己酮弥散分析中的应用

目的 了解丝网印刷作业中多个化学危害源共同作用下的环己酮弥散规律与控制特性。
方法 利用FLUENT软件对丝网印刷作业环境中环己酮的弥散过程进行数值模拟,根据监测结果和计算结果讨论丝网印刷作业环境中毒物浓度的空间分布特点,研究通风口位置、入风口风速、入风口面积、障碍物存在对环己酮弥散的影响。
结果 化学危害物浓度场可视性地揭示出化学危害物在墙壁周围和化学危害源附近容易集聚。基于不同入风口风速、不同入风口截面积、不同送风形式的化学危害物浓度模拟结果显示:（1）入风口风速为0.8 m/s时的车间内化学危害物浓度低于入风口风速为0.2 m/s时,表明入风口风速是化学危害物弥散的重要控制因素之一;（2）入风口截面积增大后,车间内气流组织形式发生变化,直接影响到气流流动速度场的改变,导致化学危害物浓度稀释而使得浓度场发生较大变化,表明入风口截面积大小同样是化学危害物弥散的重要因素之一;（3）不同的送风形式（左侧窗户或右侧窗户送风）形成的气流组织不尽相同,当气流自化学危害源上风向进入时,有利于车间内化学危害物随着气流经印刷机上方排风罩排出。
结论 利用FLUENT仿真计算进行丝网印刷作业过程中环己酮弥散分析,可以可视性地揭示化学危害物在三维空间中的分布形态和集聚规律,有利于职业病危害因素的监测和防范。
     

Respiratory protection and the risk of Mycobacterium tuberculosis infection

Tuberculosis (TB) can be transmitted to susceptible healthcare workers via inhalation of droplet nuclei carrying viable Mycobacterium tuberculosis bacilli. Several types of respiratory protective devices are compared with respect to efficacy against droplet nuclei penetration: surgical masks, disposable dust/mist particulate respirators (PRs), elastomeric halfmask respirators with high-efficiency (HEPA) filters, and powered airpurifying respirators (PAPRs) with elastomeric halfmask facepieces and HEPA filters. It is estimated that these devices permit, respectively, 42%, 5.7%, 2%, and 0.39% penetration of droplet nuclei into the facepiece. More limited data for the disposable HEPA filtering-facepiece respirator suggest that it would allow droplet nuclei penetration of 3% or less, similar to the value estimated for the elastomeric halfmask HEPA filter respirator. Because a respirator wearer's cumulative infection risk depends on the extent of droplet nuclei penetration, the cumulative risk will differ, given use of these different respirators. Hypothetical but realistic “low-exposure” and “high-exposure” scenarios are posed that involve, respectively, a 1.6% and a 6.4% annual risk of infection for healthcare workers. For the low-exposure scenario, the 10-year cumulative risks given no respirators versus surgical masks versus disposable dust/mist PRs versus elastomeric halfmask HEPA filter respirators versus HEPA filter PAPRs are, respectively, 15%, 6.7%, 0.94%, 0.33%, and .064%. For the high-exposure scenario, the 10-year cumulative risks for no respirator use versus use of the same four types of respirators are, respectively, 48%, 24%, 3.7%, 1.3%, and 0.26%. The use of disposable HEPA filtering-facepiece respirator should permit cumulative risks close to those estimated for the elastomeric halfmask HEPA filter respirator. It is concluded that when an infectious TB patient undergoes a procedure that generates respiratory aerosols, and when droplet nuclei source control is inadequate, healthcare workers attending the patient may need to wear highly protective respirators, such as HEPA filter PAPRs.     

Transfer of bacteriophage MS2 and fluorescein from N95 filtering facepiece respirators to hands: Measuring fomite potential

Contact transmission of pathogens from personal protective equipment is a concern within the healthcare industry. During public health emergency outbreaks, resources become constrained and the reuse of personal protective equipment, such as N95 filtering facepiece respirators, may be needed. This study was designed to characterize the transfer of bacteriophage MS2 and fluorescein between filtering facepiece respirators and the wearer's hands during three simulated use scenarios. Filtering facepiece respirators were contaminated with MS2 and fluorescein in droplets or droplet nuclei. Thirteen test subjects performed filtering facepiece respirator use scenarios including improper doffing, proper doffing and reuse, and improper doffing and reuse. Fluorescein and MS2 contamination transfer were quantified. The average MS2 transfer from filtering facepiece respirators to the subjects' hands ranged from 7.6–15.4% and 2.2–2.7% for droplet and droplet nuclei derived contamination, respectively. Handling filtering facepiece respirators contaminated with droplets resulted in higher levels of MS2 transfer compared to droplet nuclei for all use scenarios (p = 0.007). MS2 transfer from droplet contaminated filtering facepiece respirators during improper doffing and reuse was greater than transfer during improper doffing (p = 0.008) and proper doffing and reuse (p = 0.042). Droplet contamination resulted in higher levels of fluorescein transfer compared to droplet nuclei contaminated filtering facepiece respirators for all use scenarios (p = 0.009). Fluorescein transfer was greater for improper doffing and reuse (p = 0.007) from droplet contaminated masks compared to droplet nuclei contaminated filtering facepiece respirators and for improper doffing and reuse when compared improper doffing (p = 0.017) and proper doffing and reuse (p = 0.018) for droplet contaminated filtering facepiece respirators. For droplet nuclei contaminated filtering facepiece respirators, the difference in MS2 and fluorescein transfer did not reach statistical significance when comparing any of the use scenarios. The findings suggest that the results of fluorescein and MS2 transfer were consistent and highly correlated across the conditions of study. The data supports CDC recommendations for using proper doffing techniques and discarding filtering facepiece respirators that are directly contaminated with secretions from a cough or sneeze.     

Toward understanding the risk of secondary airborne infection: emission of respirable pathogens

Certain respiratory tract infections are transmitted through air. Coughing and sneezing by an infected person can emit pathogen-containing particles with diameters less than 10 microm that can reach the alveolar region. Based on our analysis of the sparse literature on respiratory aerosols, we estimated that emitted particles quickly decrease in diameter due to water loss to one-half the initial values, and that in one cough the volume in particles with initial diameters less than 20 microm is 60 x 10(-8) mL. The pathogen emission rate from a source case depends on the frequency of expiratory events, the respirable particle volume, and the pathogen concentration in respiratory fluid. Viable airborne pathogens are removed by exhaust ventilation, particle settling, die-off, and air disinfection methods; each removal mechanism can be assigned a first-order rate constant. The pathogen concentration in well-mixed room air depends on the emission rate, the size distribution of respirable particles carrying pathogens, and the removal rate constants. The particle settling rate and the alveolar deposition fraction depend on particle size. Given these inputs plus a susceptible person's breathing rate and exposure duration to room air, an expected alveolar dosemicrois estimated. If the infectious dose is one organism, as appears to be true for tuberculosis, infection risk is estimated by the expression: R = 1-exp(-micro). Using published tuberculosis data concerning cough frequency, bacilli concentration in respiratory fluid, and die-off rate, we illustrate the model via a plausible scenario for a person visiting the room of a pulmonary tuberculosis case. We suggest that patients termed "superspreaders" or "dangerous disseminators" are those infrequently encountered persons with high values of cough and/or sneeze frequency, elevated pathogen concentration in respiratory fluid, and/or increased respirable aerosol volume per expiratory event such that their pathogen emission rate is much higher than average.     

Ventilation rate in office buildings and sick building syndrome.

OBJECTIVE--To examine the relation between ventilation rate and occurrence of symptoms of the eyes, nose, throat, and skin as well as general symptoms such as lethargy and headache, often termed the sick building syndrome. METHODS--A cross sectional population based study was carried out in 399 workers from 14 mechanically ventilated office buildings without air recirculation or humidification, selected randomly from the Helsinki metropolitan area. The ventilation type and other characteristics of these buildings were recorded on a site visit and the ventilation in the rooms was assessed by measuring the airflow through the exhaust air outlets in the room. A questionnaire directed at workers inquired about the symptoms and perceived air quality and their possible personal and environmental determinants (response rate 81%). The outcomes were weekly work related symptoms experienced during the previous 12 months and symptom groups defined either by their anatomical location or hypothesised mechanism. RESULTS--In logistic regression analysis, the adjusted odds ratio (OR) for any symptom of interest was 3.03 (95% confidence interval (95% CI) 1.13 to 8.10) in the very low ventilation category of below 5 l/s per person and 2.24 (0.89 to 5.65) in the high ventilation category of over 25 l/s per person compared with the reference (15- < 25 l/s). The ORs for ocular (1.27, 1.11 to 1.46), nasal (1.17, 1.06 to 1.29), skin symptoms (1.18, 1.05 to 1.32), and lethargy (1.09, 1.00 to 1.19) increased significantly by a unit decrease in ventilation from 25 to 0 l/s per person. CONCLUSION--The results suggest that outdoor air ventilation rates below the optimal (15 to 25 l/s per person) increase the risk of the symptoms of sick building syndrome with the sources of pollutants present in mechanically ventilated office buildings. The Finnish guideline value is 10 l/s per person.     

Evaluation of the respiratory health of dock workers who load grain cargoes in British Columbia.

OBJECTIVES--To investigate the respiratory health of dock workers who load grain cargoes. METHODS--The respiratory health of 118 dock workers who load grain cargoes in the ports of Vancouver and Prince Rupert was compared with that of 555 grain elevator workers from the same regions. 128 civic workers were used as an unexposed control group. RESULTS--The prevalences of chronic cough and phlegm were at least as high in dock workers as those found in the elevator workers, and when adjusted for differences in duration of employment and smoking, dock workers had an eightfold higher risk of developing chronic phlegm than did civic workers. Symptoms of eye and skin irritation that were experienced at least monthly were highest for dock workers. Average percentage of the predicted FEV1 and FVC for dock workers (mean 100.6% and 105.3% respectively) were similar to the civic workers but significantly higher than those found for elevator workers. Higher subjective estimates of duration of exposure to grain dust (hours/day) were associated with lower values of FEV1. CONCLUSIONS--The more intermittent grain dust exposure patterns of dock workers may have allowed for some recovery of lung function, but chronic respiratory symptoms were less labile.