Tuberculosis Outbreak in a General Hospital: Evidence for Airborne Spread of Infection

Nj, Ehrenkranz; Jl, Kicklighter

doi:10.7326/0003-4819-77-3-377

Cited by 151 publications

(37 citation statements)

References 16 publications

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“…Even in the developed world, respiratory isolation rooms often do not deliver the recommended number of ACH [23], and many fail to maintain negative pressure and may even be under positive pressure [23–25]. Such failings have been implicated in numerous TB outbreaks [7,10,26–28]. It is therefore not surprising that we found the new mechanically ventilated facility in Lima to be poorly ventilated and in need of refurbishment to achieve negative pressure and the 12 ACH recommended for the control of TB transmission in high-risk areas [12].…”

Section: Discussionmentioning

confidence: 99%

“…Outbreaks occur in prisons [2,3], homeless shelters [4,5], and schools [6], but it is health care facilities that may pose the greatest risk from airborne contagion by congregating infectious and susceptible individuals, resulting in frequent airborne nosocomial transmission [7–11]. This public health problem is exacerbated by HIV infection, which increases both susceptibility and hospitalisation.…”

Section: Introductionmentioning

confidence: 99%

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Natural Ventilation for the Prevention of Airborne Contagion

et al. 2007

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BackgroundInstitutional transmission of airborne infections such as tuberculosis (TB) is an important public health problem, especially in resource-limited settings where protective measures such as negative-pressure isolation rooms are difficult to implement. Natural ventilation may offer a low-cost alternative. Our objective was to investigate the rates, determinants, and effects of natural ventilation in health care settings.Methods and FindingsThe study was carried out in eight hospitals in Lima, Peru; five were hospitals of “old-fashioned” design built pre-1950, and three of “modern” design, built 1970–1990. In these hospitals 70 naturally ventilated clinical rooms where infectious patients are likely to be encountered were studied. These included respiratory isolation rooms, TB wards, respiratory wards, general medical wards, outpatient consulting rooms, waiting rooms, and emergency departments. These rooms were compared with 12 mechanically ventilated negative-pressure respiratory isolation rooms built post-2000. Ventilation was measured using a carbon dioxide tracer gas technique in 368 experiments. Architectural and environmental variables were measured. For each experiment, infection risk was estimated for TB exposure using the Wells-Riley model of airborne infection. We found that opening windows and doors provided median ventilation of 28 air changes/hour (ACH), more than double that of mechanically ventilated negative-pressure rooms ventilated at the 12 ACH recommended for high-risk areas, and 18 times that with windows and doors closed (p < 0.001). Facilities built more than 50 years ago, characterised by large windows and high ceilings, had greater ventilation than modern naturally ventilated rooms (40 versus 17 ACH; p < 0.001). Even within the lowest quartile of wind speeds, natural ventilation exceeded mechanical (p < 0.001). The Wells-Riley airborne infection model predicted that in mechanically ventilated rooms 39% of susceptible individuals would become infected following 24 h of exposure to untreated TB patients of infectiousness characterised in a well-documented outbreak. This infection rate compared with 33% in modern and 11% in pre-1950 naturally ventilated facilities with windows and doors open.ConclusionsOpening windows and doors maximises natural ventilation so that the risk of airborne contagion is much lower than with costly, maintenance-requiring mechanical ventilation systems. Old-fashioned clinical areas with high ceilings and large windows provide greatest protection. Natural ventilation costs little and is maintenance free, and is particularly suited to limited-resource settings and tropical climates, where the burden of TB and institutional TB transmission is highest. In settings where respiratory isolation is difficult and climate permits, windows and doors should be opened to reduce the risk of airborne contagion.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Natural Ventilation for the Prevention of Airborne Contagion

et al. 2007

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“…Contributing factors in the eight reports of outbreaks related to single patients (summarized in Table 3) were delayed diagnosis (in seven of the eight) 47,48,50-54 ; poor ventilation with positive pressure in isolation rooms or high levels of air recirculation (or both) [47][48][49]52 ; and aerosolization of bacilli through mechanical ventilation, [47][48][49] bronchoscopy, 48 dressing change, 54 jet irrigation of a thigh abscess, 52 or autopsy. 50,51 Transmission during autopsy occurred despite a ventilation rate of 11 air changes per hour, 50 suggesting massive aerosolization of infectious particles, which may explain why workers who assist in autopsies have higher rates of disease than other health care workers.…”

Section: R Eports Of N Osocomial T Ransmissionmentioning

confidence: 99%

“…40,48,49,55 The duration of exposure usually refers to the duration of direct contact with patients, but workers with no direct contact may be ex-posed in other parts of the same building because of air-flow patterns 52 or recirculation of exhaust air from the rooms of infected patients. 47,49,55 For each complete exchange of indoor air with outdoor air (one air change) the concentration of infectious particles is reduced by 63 percent; with six air changes, the concentration is reduced by 99 percent. 59…”

Section: T Heoretical B Asis For N Osocomial T Ransmission Of T Ubercmentioning

confidence: 99%

Tuberculosis among Health Care Workers

et al. 1995

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“…Further, much of the literature has focused on risks to physicians, nurses, technicians, and others with close patient contact. Several studies have included small numbers of ward clerks and others who do not have close patient contact, but these have typically been in the setting of a TB outbreak or in the presence of a particularly infectious patient [Ehrenkranz et al, 1972;Beck-Sagué et al, 1992;Catanzaro, 1982]. Such studies focus on contact investigation for the purpose of tracking outbreaks of disease.…”

Section: Introductionmentioning

confidence: 99%