Inhaling to mitigate exhaled bioaerosols
14 Dec 2004-Proceedings of the National Academy of Sciences of the United States of America (National Academy of Sciences)-Vol. 101, Iss: 50, pp 17383-17388
TL;DR: It is hypothesized that, by altering lung airway surface properties through an inhaled nontoxic aerosol, this work might substantially diminish the number of exhaled bioaerosol droplets and thereby provide a simple means to potentially mitigate the spread of airborne infectious disease independently of the identity of the airborne pathogen or the nature of any specific therapy.
Abstract: Humans commonly exhale aerosols comprised of small droplets of airway-lining fluid during normal breathing. These “exhaled bioaerosols” may carry airborne pathogens and thereby magnify the spread of certain infectious diseases, such as influenza, tuberculosis, and severe acute respiratory syndrome. We hypothesize that, by altering lung airway surface properties through an inhaled nontoxic aerosol, we might substantially diminish the number of exhaled bioaerosol droplets and thereby provide a simple means to potentially mitigate the spread of airborne infectious disease independently of the identity of the airborne pathogen or the nature of any specific therapy. We find that some normal human subjects expire many more bioaerosol particles than other individuals during quiet breathing and therefore bear the burden of production of exhaled bioaerosols. Administering nebulized isotonic saline to these “high-producer” individuals diminishes the number of exhaled bioaerosol particles expired by 72.10 ± 8.19% for up to 6 h. In vitro and in vivo experiments with saline and surfactants suggest that the mechanism of action of the nebulized saline relates to modification of the physical properties of the airway-lining fluid, notably surface tension.
Citations
More filters
TL;DR: It is shown that contact tracing data from eight directly transmitted diseases shows that the distribution of individual infectiousness around R0 is often highly skewed, and implications for outbreak control are explored, showing that individual-specific control measures outperform population-wide measures.
Abstract: Population-level analyses often use average quantities to describe heterogeneous systems, particularly when variation does not arise from identifiable groups. A prominent example, central to our current understanding of epidemic spread, is the basic reproductive number, R(0), which is defined as the mean number of infections caused by an infected individual in a susceptible population. Population estimates of R(0) can obscure considerable individual variation in infectiousness, as highlighted during the global emergence of severe acute respiratory syndrome (SARS) by numerous 'superspreading events' in which certain individuals infected unusually large numbers of secondary cases. For diseases transmitted by non-sexual direct contacts, such as SARS or smallpox, individual variation is difficult to measure empirically, and thus its importance for outbreak dynamics has been unclear. Here we present an integrated theoretical and statistical analysis of the influence of individual variation in infectiousness on disease emergence. Using contact tracing data from eight directly transmitted diseases, we show that the distribution of individual infectiousness around R(0) is often highly skewed. Model predictions accounting for this variation differ sharply from average-based approaches, with disease extinction more likely and outbreaks rarer but more explosive. Using these models, we explore implications for outbreak control, showing that individual-specific control measures outperform population-wide measures. Moreover, the dramatic improvements achieved through targeted control policies emphasize the need to identify predictive correlates of higher infectiousness. Our findings indicate that superspreading is a normal feature of disease spread, and to frame ongoing discussion we propose a rigorous definition for superspreading events and a method to predict their frequency.
2,274 citations
TL;DR: In this article, a new expiratory droplet investigation system (EDIS) was used to conduct the most comprehensive program of study to date, of the dilution corrected droplet size distributions produced during different respiratory activities.
850 citations
TL;DR: It is shown that the rate of particle emission during normal human speech is positively correlated with the loudness (amplitude) of vocalization, and the phenomenon of speech superemission cannot be fully explained either by the phonic structures or the amplitude of the speech.
Abstract: Mechanistic hypotheses about airborne infectious disease transmission have traditionally emphasized the role of coughing and sneezing, which are dramatic expiratory events that yield both easily visible droplets and large quantities of particles too small to see by eye. Nonetheless, it has long been known that normal speech also yields large quantities of particles that are too small to see by eye, but are large enough to carry a variety of communicable respiratory pathogens. Here we show that the rate of particle emission during normal human speech is positively correlated with the loudness (amplitude) of vocalization, ranging from approximately 1 to 50 particles per second (0.06 to 3 particles per cm3) for low to high amplitudes, regardless of the language spoken (English, Spanish, Mandarin, or Arabic). Furthermore, a small fraction of individuals behaves as "speech superemitters," consistently releasing an order of magnitude more particles than their peers. Our data demonstrate that the phenomenon of speech superemission cannot be fully explained either by the phonic structures or the amplitude of the speech. These results suggest that other unknown physiological factors, varying dramatically among individuals, could affect the probability of respiratory infectious disease transmission, and also help explain the existence of superspreaders who are disproportionately responsible for outbreaks of airborne infectious disease.
750 citations
TL;DR: Arguments supporting an important role for aerosol transmission that were reviewed included prolonged survival of the virus in aerosol suspensions, demonstration of the low infectious dose required for aerosoli transmission in human volunteers, and clinical and epidemiological observations were disentanglements of large droplets and aerosol Transmission was possible.
Abstract: Over the past few years, prompted by pandemic preparedness initiatives, the debate over the modes of transmission of influenza has been rekindled and several reviews have appeared. Arguments supporting an important role for aerosol transmission that were reviewed included prolonged survival of the virus in aerosol suspensions, demonstration of the low infectious dose required for aerosol transmission in human volunteers, and clinical and epidemiological observations were disentanglements of large droplets and aerosol transmission was possible. Since these reviews were published, several new studies have been done and generated new data. These include direct demonstration of the presence of influenza viruses in aerosolized droplets from the tidal breathing of infected persons and in the air of an emergency department; the establishment of the guinea pig model for influenza transmission, where it was shown that aerosol transmission is important and probably modulated by temperature and humidity; the demonstration of some genetic determinants of airborne transmission of influenza viruses as assessed using the ferret model; and mathematical modelling studies that strongly support the aerosol route. These recent results and their implication for infection control of influenza are discussed in this review.
536 citations
Cites background from "Inhaling to mitigate exhaled bioaer..."
...A recent study (Edwards et al. 2004) has confirmed the production of aerosol size particles by normal breathing, and confirmed that the size of the majority of the particles exhaled by mouth is 1 mm or less....
[...]
...Another remarkable finding is that there is considerable heterogeneity in aerosol production between individuals, consistently over time (Edwards et al. 2004)....
[...]
TL;DR: Expelled particles carrying pathogens do not exclusively disperse by airborne or droplet transmission but avail of both methods simultaneously and current dichotomous infection control precautions should be updated to include measures to contain both modes of aerosolised transmission.
536 citations
References
More filters
Book•
01 Jan 2007
TL;DR: This book discusses water Microbiology in Public Health, soil, Rhizosphere and Phyllosphere, and the role of aerobiology in these environments.
Abstract: Section I: Introduction to Environmental Microbiology Section II: General Methodology Section III: Water Microbiology in Public Health Section IV: Aquatic Environments Section V: Soil, Rhizosphere and Phyllosphere Section VI: Subsurface and Landfills Section VII: Aerobiology Section VIII: Biotransformation and Biodegradation
1,489 citations
TL;DR: The Working Group on Civilian Biodefense has developed consensus-based recommendations for measures to be taken by medical and public health professionals if tularemia is used as a biological weapon against a civilian population.
Abstract: ObjectiveThe Working Group on Civilian Biodefense has developed consensus-based
recommendations for measures to be taken by medical and public health professionals
if tularemia is used as a biological weapon against a civilian population.ParticipantsThe working group included 25 representatives from academic medical
centers, civilian and military governmental agencies, and other public health
and emergency management institutions and agencies.EvidenceMEDLINE databases were searched from January 1966 to October 2000, using
the Medical Subject Headings Francisella tularensis, Pasteurella tularensis, biological weapon, biological terrorism, bioterrorism, biological warfare, and biowarfare. Review of these references led to identification
of relevant materials published prior to 1966. In addition, participants identified
other references and sources.Consensus ProcessThree formal drafts of the statement that synthesized information obtained
in the formal evidence-gathering process were reviewed by members of the working
group. Consensus was achieved on the final draft.ConclusionsA weapon using airborne tularemia would likely result 3 to 5 days later
in an outbreak of acute, undifferentiated febrile illness with incipient pneumonia,
pleuritis, and hilar lymphadenopathy. Specific epidemiological, clinical,
and microbiological findings should lead to early suspicion of intentional
tularemia in an alert health system; laboratory confirmation of agent could
be delayed. Without treatment, the clinical course could progress to respiratory
failure, shock, and death. Prompt treatment with streptomycin, gentamicin,
doxycycline, or ciprofloxacin is recommended. Prophylactic use of doxycycline
or ciprofloxacin may be useful in the early postexposure period.
1,297 citations
TL;DR: A measles epidemic in a modern suburban elementary school in upstate New York in spring, 1974, is analyzed in terms of a model which provides a basis for apportioning the chance of infection from classmates sharing the same home room, from airborne organisms recirculated by the ventilating system, and from exposure in school buses.
Abstract: A measles epidemic in a modern suburban elementary school in upstate New York in spring, 1974, is analyzed in terms of a model which provides a basis for apportioning the chance of infection from classmates sharing the same home room, from airborne organisms recirculated by the ventilating system, and from exposure in school buses. The epidemic was notable because of its explosive nature and its occurrence in a school where 97% of the children had been vaccinated. Many had been vaccinated at less than one year of age. The index case was a girl in second grade who produced 28 secondary cases in 14 different classrooms. Organisms recirculated by the ventilating system were strongly implicated. After two subsequent generations, 60 children had been infected, and the epidemic subsided. From estimates of major physical and biologic factors, it was possible to calculate that the index case produced approximately 93 units of airborne infection (quanta) per minute. The epidemic pattern suggested that the secondaries were less infectious by an order of magnitude. The exceptional infectiousness of the index case, inadequate immunization of many of the children, and the high percentage of air recirculated throughout the school, are believed to account for the extent and sharpness of the outbreak.
709 citations
TL;DR: C coughing produced the largest droplet concentrations and nose breathing the least, although considerable intersubject variability was observed, and the existence of larger sized droplets in the exhaled breath was confirmed.
Abstract: Droplets carried in exhaled breath may carry microorganisms capable of transmitting disease over both short and long distances. The size distribution of such droplets will influence the type of organisms that may be carried as well as strategies for controlling airborne infection. The aim of this study was to characterize the size distribution of droplets exhaled by healthy individuals. Exhaled droplets from human subjects performing four respiratory actions (mouth breathing, nose breathing, coughing, talking) were measured by both an optical particle counter (OPC) and an analytical transmission electron microscope (AEM). The OPC indicated a preponderance of particles less than 1 mu, although larger particles were also found. Measurements with the AEM confirmed the existence of larger sized droplets in the exhaled breath. In general, coughing produced the largest droplet concentrations and nose breathing the least, although considerable intersubject variability was observed.
630 citations
TL;DR: Quantification of viable cough-generated aerosols is feasible and offers a new approach to study infectiousness and transmission of M. tuberculosis and other airborne pathogens.
Abstract: The concentration and size distribution of infectious aerosols produced by patients with pulmonary tuberculosis (TB) has never been directly measured. We aimed to assess the feasibility of a method that we developed to collect and quantify culturable cough-generated aerosols of Mycobacterium tuberculosis. Subjects were recruited from a referral hospital and most had multidrug-resistant TB. They coughed into a chamber containing microbial air samplers while cough frequency was measured during two 5-minute sessions. Cough-generated aerosol cultures were positive in 4 of 16 subjects (25%) with smear-positive pulmonary TB. There was a rapid decrease in the cough-generated aerosol cultures within the first 3 weeks of effective treatment. Culture-positive cough aerosols were associated with lack of treatment during the previous week (p = 0.007), and there was a trend in the association with cough frequency (p = 0.08). The size distributions of these aerosols were variable, but most particle sizes were in the respirable range. Quantification of viable cough-generated aerosols is feasible and offers a new approach to study infectiousness and transmission of M. tuberculosis and other airborne pathogens.
316 citations