Your browser doesn't support javascript.
Show: 20 | 50 | 100
Results 1 - 20 de 49
Filter
2.
Ann Intern Med ; 174(12): 1710-1718, 2021 12.
Article in English | MEDLINE | ID: covidwho-1506230

ABSTRACT

Policies to prevent respiratory virus transmission in health care settings have traditionally divided organisms into Droplet versus Airborne categories. Droplet organisms (for example, influenza) are said to be transmitted via large respiratory secretions that rapidly fall to the ground within 1 to 2 meters and are adequately blocked by surgical masks. Airborne pathogens (for example, measles), by contrast, are transmitted by aerosols that are small enough and light enough to carry beyond 2 meters and to penetrate the gaps between masks and faces; health care workers are advised to wear N95 respirators and to place these patients in negative-pressure rooms. Respirators and negative-pressure rooms are also recommended when caring for patients with influenza or SARS-CoV-2 who are undergoing "aerosol-generating procedures," such as intubation. An increasing body of evidence, however, questions this framework. People routinely emit respiratory particles in a range of sizes, but most are aerosols, and most procedures do not generate meaningfully more aerosols than ordinary breathing, and far fewer than coughing, exercise, or labored breathing. Most transmission nonetheless occurs at close range because virus-laden aerosols are most concentrated at the source; they then diffuse and dilute with distance, making long-distance transmission rare in well-ventilated spaces. The primary risk factors for nosocomial transmission are community incidence rates, viral load, symptoms, proximity, duration of exposure, and poor ventilation. Failure to appreciate these factors may lead to underappreciation of some risks (for example, overestimation of the protection provided by medical masks, insufficient attention to ventilation) or misallocation of limited resources (for example, reserving N95 respirators and negative-pressure rooms only for aerosol-generating procedures or requiring negative-pressure rooms for all patients with SARS-CoV-2 infection regardless of stage of illness). Enhanced understanding of the factors governing respiratory pathogen transmission may inform the development of more effective policies to prevent nosocomial transmission of respiratory pathogens.


Subject(s)
Infection Control/methods , Respiratory Tract Infections/transmission , Respiratory Tract Infections/virology , Aerosols , COVID-19/prevention & control , COVID-19/transmission , COVID-19/virology , Cross Infection/prevention & control , Cross Infection/virology , Health Policy , Humans , Infectious Disease Transmission, Patient-to-Professional/prevention & control , Influenza, Human/prevention & control , Influenza, Human/transmission , Influenza, Human/virology , Masks , Personnel, Hospital , SARS-CoV-2 , United States/epidemiology , Ventilation
3.
Indoor Air ; 32(1): e12946, 2022 01.
Article in English | MEDLINE | ID: covidwho-1494731

ABSTRACT

To explain the observed phenomenon that most SARS-CoV-2 transmission occurs indoors whereas its outdoor transmission is rare, a simple macroscopic aerosol balance model is developed to link short- and long-range airborne transmission. The model considers the involvement of exhaled droplets with initial diameter ≤50 µm in the short-range airborne route, whereas only a fraction of these droplets with an initial diameter within 15 µm or equivalently a final diameter within 5 µm considered in the long-range airborne route. One surprising finding is that the room ventilation rate significantly affects the short-range airborne route, in contrast to traditional belief. When the ventilation rate in a room is insufficient, the airborne infection risks due to both short- and long-range transmission are high. A ventilation rate of 10 L/s per person provides a similar concentration vs distance decay profile to that in outdoor settings, which provides additional justification for the widely adopted ventilation standard of 10 L/s per person. The newly obtained data do not support the basic assumption in the existing ventilation standard ASHRAE 62.1 (2019) that the required people outdoor air rate is constant if the standard is used directly for respiratory infection control. Instead, it is necessary to increase the ventilation rate when the physical distance between people is less than approximately 2 m.


Subject(s)
Air Microbiology , Air Pollution, Indoor , COVID-19 , Respiratory Tract Infections , Ventilation , Aerosols , COVID-19/transmission , Humans , Respiratory Tract Infections/transmission , SARS-CoV-2
4.
Infect Dis Clin North Am ; 35(4): 1055-1075, 2021 12.
Article in English | MEDLINE | ID: covidwho-1487740

ABSTRACT

Health care-acquired viral respiratory infections are common and cause increased patient morbidity and mortality. Although the threat of viral respiratory infection has been underscored by the coronavirus disease 2019 (COVID-19) pandemic, respiratory viruses have a significant impact in health care settings even under normal circumstances. Studies report decreased nosocomial transmission when aggressive infection control measures are implemented, with more success noted when using a multicomponent approach. Influenza vaccination of health care personnel furthers decrease rates of transmission; thus, mandatory vaccination is becoming more common. This article discusses the epidemiology, transmission, and control of health care-associated respiratory viral infections.


Subject(s)
Cross Infection/prevention & control , Cross Infection/virology , Respiratory Tract Infections/prevention & control , Respiratory Tract Infections/virology , COVID-19/epidemiology , COVID-19/prevention & control , COVID-19/transmission , Cross Infection/epidemiology , Cross Infection/transmission , Guideline Adherence , Health Personnel/standards , Humans , Infection Control/standards , Respiratory Tract Infections/epidemiology , Respiratory Tract Infections/transmission , SARS-CoV-2/pathogenicity , Vaccination , Viruses/classification , Viruses/pathogenicity
5.
PLoS Comput Biol ; 17(10): e1009363, 2021 10.
Article in English | MEDLINE | ID: covidwho-1468148

ABSTRACT

The spread of a communicable disease is a complex spatio-temporal process shaped by the specific transmission mechanism, and diverse factors including the behavior, socio-economic and demographic properties of the host population. While the key factors shaping transmission of influenza and COVID-19 are beginning to be broadly understood, making precise forecasts on case count and mortality is still difficult. In this study we introduce the concept of a universal geospatial risk phenotype of individual US counties facilitating flu-like transmission mechanisms. We call this the Universal Influenza-like Transmission (UnIT) score, which is computed as an information-theoretic divergence of the local incidence time series from an high-risk process of epidemic initiation, inferred from almost a decade of flu season incidence data gleaned from the diagnostic history of nearly a third of the US population. Despite being computed from the past seasonal flu incidence records, the UnIT score emerges as the dominant factor explaining incidence trends for the COVID-19 pandemic over putative demographic and socio-economic factors. The predictive ability of the UnIT score is further demonstrated via county-specific weekly case count forecasts which consistently outperform the state of the art models throughout the time-line of the COVID-19 pandemic. This study demonstrates that knowledge of past epidemics may be used to chart the course of future ones, if transmission mechanisms are broadly similar, despite distinct disease processes and causative pathogens.


Subject(s)
COVID-19/epidemiology , Forecasting , Respiratory Tract Infections/epidemiology , Geographic Information Systems , Humans , Incidence , Influenza, Human/epidemiology , Local Government , Models, Biological , Respiratory Tract Infections/transmission , United States/epidemiology
7.
Int J Infect Dis ; 104: 198-206, 2021 Mar.
Article in English | MEDLINE | ID: covidwho-1385702

ABSTRACT

INTRODUCTION: Synthesis of the available evidence on the effectiveness of medical and cloth facemask use by the general public in community settings is required to learn lessons for future respiratory epidemics/pandemics. METHOD: Search terms relating to facemasks, infection and community settings were used for PubMed, the Cochrane Library Database and Google Scholar. A meta-analysis was conducted using a random-effects model. RESULTS: The review included 12 primary studies on the effectiveness of medical facemask use to prevent influenza, influenza-like illness, SARS-CoV, and SARS-CoV-2 transmission. The meta-analysis demonstrated that facemask use significantly reduces the risk of transmitting these respiratory infections (pooled OR = 0.66, 95% CI 0.54-0.81). Of the 12 studies, 10 clinical trials suggested that respiratory infection incidence is lower with high medical facemask compliance, early use and use in combination with intensive hand hygiene. One cohort study conducted during the SARS-CoV-2 pandemic demonstrated that facemasks are effective in reducing SARS-CoV-2 transmission when used before those who are infected develop symptoms. One case-control study reported that controls used medical facemasks more often than cases infected with SARS-CoV (p < 0.05). No primary study on cloth facemask effectiveness to prevent respiratory infection transmission was found. CONCLUSION: Based on the available evidence, medical facemask use by healthy and sick individuals is recommended for preventing respiratory infection transmission in community settings. Medical facemask effectiveness is dependent on compliance and utilization in combination with preventive measures such as intensive hand hygiene. No direct evidence is currently available in humans supporting the recommendation of cloth facemask use to prevent respiratory infection transmission.


Subject(s)
COVID-19/prevention & control , Influenza, Human/prevention & control , Masks , Pandemics/prevention & control , Respiratory Tract Infections/prevention & control , Severe Acute Respiratory Syndrome/prevention & control , COVID-19/transmission , COVID-19/virology , Case-Control Studies , Cohort Studies , Hand Hygiene , Humans , Influenza, Human/transmission , Influenza, Human/virology , Respiratory Tract Infections/transmission , Respiratory Tract Infections/virology , Severe Acute Respiratory Syndrome/transmission , Severe Acute Respiratory Syndrome/virology
9.
Future Microbiol ; 16: 1105-1133, 2021 09.
Article in English | MEDLINE | ID: covidwho-1381356

ABSTRACT

SARS-CoV-2 is the etiological agent of the current pandemic worldwide and its associated disease COVID-19. In this review, we have analyzed SARS-CoV-2 characteristics and those ones of other well-known RNA viruses viz. HIV, HCV and Influenza viruses, collecting their historical data, clinical manifestations and pathogenetic mechanisms. The aim of the work is obtaining useful insights and lessons for a better understanding of SARS-CoV-2. These pathogens present a distinct mode of transmission, as SARS-CoV-2 and Influenza viruses are airborne, whereas HIV and HCV are bloodborne. However, these viruses exhibit some potential similar clinical manifestations and pathogenetic mechanisms and their understanding may contribute to establishing preventive measures and new therapies against SARS-CoV-2.


Subject(s)
COVID-19/history , Pandemics/history , SARS-CoV-2/physiology , SARS-CoV-2/pathogenicity , Antiviral Agents/therapeutic use , COVID-19/drug therapy , COVID-19/epidemiology , COVID-19/transmission , Climate , Disease Reservoirs/virology , Genome, Viral , History, 19th Century , History, 20th Century , History, 21st Century , Humans , Mutation , RNA Viruses/pathogenicity , RNA Viruses/physiology , Reinfection/epidemiology , Reinfection/history , Reinfection/transmission , Reinfection/virology , Respiratory Tract Infections/drug therapy , Respiratory Tract Infections/epidemiology , Respiratory Tract Infections/history , Respiratory Tract Infections/transmission , Virus Replication
10.
Science ; 373(6558)2021 08 27.
Article in English | MEDLINE | ID: covidwho-1376452

ABSTRACT

The COVID-19 pandemic has revealed critical knowledge gaps in our understanding of and a need to update the traditional view of transmission pathways for respiratory viruses. The long-standing definitions of droplet and airborne transmission do not account for the mechanisms by which virus-laden respiratory droplets and aerosols travel through the air and lead to infection. In this Review, we discuss current evidence regarding the transmission of respiratory viruses by aerosols-how they are generated, transported, and deposited, as well as the factors affecting the relative contributions of droplet-spray deposition versus aerosol inhalation as modes of transmission. Improved understanding of aerosol transmission brought about by studies of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection requires a reevaluation of the major transmission pathways for other respiratory viruses, which will allow better-informed controls to reduce airborne transmission.


Subject(s)
Air Microbiology , COVID-19/transmission , Respiratory Tract Infections/transmission , SARS-CoV-2 , Virus Diseases/transmission , Virus Physiological Phenomena , Aerosols , COVID-19/virology , Disease Transmission, Infectious , Humans , Microbial Viability , Particle Size , Respiratory System/virology , Respiratory Tract Infections/virology , SARS-CoV-2/isolation & purification , SARS-CoV-2/physiology , Viral Load , Virus Diseases/virology , Viruses/isolation & purification
11.
J Breath Res ; 15(4)2021 09 13.
Article in English | MEDLINE | ID: covidwho-1361738

ABSTRACT

During the ongoing COVID-19 pandemic, face masks are among the most common and practical control measures used globally in reducing the risk of infection and disease transmission. Although several studies have investigated the efficacy of various face masks and respirators in preventing infection, the results have been inconsistent. Therefore, we performed a systematic review and network meta-analysis (NMA) of the randomized-controlled trials (RCTs) to assess the actual efficacy of face masks in preventing respiratory infections. We searched nine electronic databases up to July 2020 to find potential articles. We accepted trials reporting the protective efficacy of face masks against respiratory infections, of which the primary endpoint was the presence of respiratory infections. We used the ROB-2 Cochrane tool to grade the trial quality. We initially registered the protocol for this study in PROSPERO (CRD42020178516). Sixteen RCTs involving 17 048 individuals were included for NMA. Overall, evidence was weak, lacking statistical power due to the small number of participants, and there was substantial inconsistency in our findings. In comparison to those without face masks, participants with fit-tested N95 respirators were likely to have lesser infection risk (RR 0.67, 95% CI 0.38-1.19,P-score 0.80), followed by those with non-fit-tested N95 and non-fit-tested FFP2 respirators that shared the similar risk, (RR 0.73, 95% CI 0.12-4.36,P-score 0.63) and (RR 0.80, 95% CI 0.38-1.71,P-score 0.63), respectively. Next, participants who donned face masks with and without hand hygiene practices showed modest risk improvement alike (RR 0.89, 95% CI 0.67-1.17,P-score 0.55) and (RR 0.92, 95% CI 0.70-1.22,P-score 0.51). Otherwise, participants donning double-layered cloth masks were prone to infection (RR 4.80, 95% CI 1.42-16.27,P-score 0.01). Eleven out of 16 RCTs that underwent a pairwise meta-analysis revealed a substantially lower infection risk in those donning medical face masks (MFMs) than those without face masks (RR 0.83 95% CI 0.71-0.96). Given the body of evidence through a systematic review and meta-analyses, our findings supported the protective benefits of MFMs in reducing respiratory transmissions, and the universal mask-wearing should be applied-especially during the COVID-19 pandemic. More clinical data is required to conclude the efficiency of cloth masks; in the short term, users should not use cloth face masks in the outbreak hot spots and places where social distancing is impossible.


Subject(s)
COVID-19/prevention & control , Communicable Disease Control , Infectious Disease Transmission, Patient-to-Professional/prevention & control , Masks , Respiratory Protective Devices , Respiratory Tract Infections/prevention & control , Breath Tests , Humans , Network Meta-Analysis , Occupational Exposure , Randomized Controlled Trials as Topic , Respiratory Tract Infections/transmission , SARS-CoV-2
12.
Pediatr Infect Dis J ; 40(10): e379-e381, 2021 10 01.
Article in English | MEDLINE | ID: covidwho-1355794

ABSTRACT

This brief report presents transmission rates from a prospective study of 15 households with pediatric index cases of severe acute respiratory coronavirus-2 in Los Angeles County from December 2020 to February 2021. Our findings support ongoing evidence that transmission from pediatric index cases to household contacts is frequent but can be mitigated with practicing well-documented control measures at home, including isolation, masking and good hand hygiene.


Subject(s)
COVID-19/transmission , Respiratory Tract Infections/transmission , Adolescent , Child , Child, Preschool , Family Characteristics , Female , Hand Hygiene/methods , Humans , Los Angeles , Male , Masks , Prospective Studies , SARS-CoV-2/pathogenicity , Social Isolation
14.
Salud Publica Mex ; 63(2, Mar-Abr): 225-231, 2021 Feb 26.
Article in Spanish | MEDLINE | ID: covidwho-1310306

ABSTRACT

Objetivo. Determinar el nivel de evidencia sobre la proba-bilidad de transmisión de enfermedades respiratorias agudas en el transporte público colectivo. Material y métodos. Se utilizó la metodología de revisiones rápidas de Cochrane. La estrategia de búsqueda abarcó una base de datos acadé-mica hasta el 10 de diciembre de 2020. Resultados. Se identificaron 16 manuscritos que cumplieron los criterios de selección. En estudios de cohorte agrupados se encontró que el momio de seroconversión por influenza A o B fue 54% mayor en personas con uso frecuente de transporte público colectivo en comparación con las personas con un uso poco frecuente (razón de momios: 1.54; IC95%:1.06-2.01). Conclusión. La probabilidad de contagio por enfermeda-des respiratorias agudas puede incrementar con el uso del transporte público colectivo. Algunas recomendaciones para reducir la probabilidad de contagio en el transporte público colectivo son el uso de cubrebocas y reducir el número de pasajeros y tiempo de traslado.


Subject(s)
Public Sector , Respiratory Tract Infections , Transportation , Humans , Probability , Respiratory Tract Infections/transmission , Transportation/statistics & numerical data
15.
Salud Publica Mex ; 63(2, Mar-Abr): 232-241, 2021 Feb 26.
Article in Spanish | MEDLINE | ID: covidwho-1310300

ABSTRACT

 Objetivo. Describir la evidencia disponible sobre la trans-misión por Covid-19 e infecciones respiratorias agudas simi-lares al Covid-19 en espacios públicos abiertos. Material y métodos. La búsqueda incluyó 4 926 artículos en inglés de los años 2000 a 2020. Seis investigadores revisaron el título y el resumen de los artículos de Embase y PubMed; dos inves-tigadores revisaron los de medRxiv. Todos los investigadores revisaron textos completos y otros resolvieron las discre-pancias. Resultados. De los 21 artículos seleccionados, se observó que la presencia de virus en superficies públicas, aguas residuales y áreas exteriores no fue indicativa de trans-misión. No obstante, se observó que el uso de cubrebocas, el lavado de manos, el distanciamiento social, no asistir a eventos masivos y la movilidad individual a espacios públicos podría ayudar a reducir el riesgo de transmisión. Conclusión. Esta información podría coadyuvar a generar recomendaciones en salud pública, sin embargo, es recomendable actualizar esta revisión conforme avance la evidencia científica.


Subject(s)
COVID-19/transmission , Respiratory Tract Infections/transmission , Acute Disease , Humans
17.
Nat Commun ; 12(1): 3249, 2021 05 31.
Article in English | MEDLINE | ID: covidwho-1249208

ABSTRACT

Coronavirus disease 2019 (COVID-19) was detected in China during the 2019-2020 seasonal influenza epidemic. Non-pharmaceutical interventions (NPIs) and behavioral changes to mitigate COVID-19 could have affected transmission dynamics of influenza and other respiratory diseases. By comparing 2019-2020 seasonal influenza activity through March 29, 2020 with the 2011-2019 seasons, we found that COVID-19 outbreaks and related NPIs may have reduced influenza in Southern and Northern China and the United States by 79.2% (lower and upper bounds: 48.8%-87.2%), 79.4% (44.9%-87.4%) and 67.2% (11.5%-80.5%). Decreases in influenza virus infection were also associated with the timing of NPIs. Without COVID-19 NPIs, influenza activity in China and the United States would likely have remained high during the 2019-2020 season. Our findings provide evidence that NPIs can partially mitigate seasonal and, potentially, pandemic influenza.


Subject(s)
COVID-19/epidemiology , Influenza, Human/epidemiology , Models, Statistical , Pandemics , Respiratory Tract Infections/epidemiology , COVID-19/transmission , COVID-19/virology , China/epidemiology , Humans , Influenza, Human/transmission , Influenza, Human/virology , Orthomyxoviridae/pathogenicity , Orthomyxoviridae/physiology , Personal Protective Equipment , Physical Distancing , Quarantine/organization & administration , Respiratory Tract Infections/transmission , Respiratory Tract Infections/virology , SARS-CoV-2/pathogenicity , SARS-CoV-2/physiology , Seasons , United States/epidemiology
18.
Viruses ; 13(4)2021 03 24.
Article in English | MEDLINE | ID: covidwho-1231502

ABSTRACT

Redondoviridae is a recently discovered DNA virus family consisting of two species, vientovirus and brisavirus. Here we used PCR amplification and sequencing to characterize redondoviruses in nasal/throat swabs collected longitudinally from a cohort of 58 individuals working with animals in Vietnam. We additionally analyzed samples from animals to which redondovirus DNA-positive participants were exposed. Redondoviruses were detected in approximately 60% of study participants, including 33% (30/91) of samples collected during episodes of acute respiratory disease and in 50% (29/58) of baseline samples (with no respiratory symptoms). Vientovirus (73%; 24/33) was detected more frequently in samples than brisaviruses (27%; 9/33). In the 23 participants with at least 2 redondovirus-positive samples among their longitudinal samples, 10 (43.5%) had identical redondovirus replication-gene sequences detected (sampling duration: 35-132 days). We found no identical redondovirus replication genes in samples from different participants, and no redondoviruses were detected in 53 pooled nasal/throat swabs collected from domestic animals. Phylogenetic analysis described no large-scale geographical clustering between viruses from Vietnam, the US, Spain, and China, indicating that redondoviruses are highly genetically diverse and have a wide geographical distribution. Collectively, our study provides novel insights into the Redondoviridae family in humans, describing a high prevalence, potentially associated with chronic shedding in the respiratory tract with lack of evidence of zoonotic transmission from close animal contacts. The tropism and potential pathogenicity of this viral family remain to be determined.


Subject(s)
DNA Viruses/genetics , DNA Viruses/physiology , Respiratory Tract Infections/epidemiology , Respiratory Tract Infections/virology , Viral Zoonoses/epidemiology , Virus Shedding , Adolescent , Adult , Aged , Animals , Child , Cohort Studies , DNA Viruses/classification , Farmers/statistics & numerical data , Female , Humans , Longitudinal Studies , Male , Middle Aged , Nose/virology , Pharynx/virology , Phylogeny , Prevalence , Respiratory Tract Infections/transmission , Sequence Analysis, DNA , Vietnam/epidemiology , Viral Zoonoses/transmission , Young Adult
20.
BMC Infect Dis ; 21(1): 335, 2021 Apr 09.
Article in English | MEDLINE | ID: covidwho-1175296

ABSTRACT

BACKGROUND: Unusually high snowfall in western Washington State in February 2019 led to widespread school and workplace closures. We assessed the impact of social distancing caused by this extreme weather event on the transmission of respiratory viruses. METHODS: Residual specimens from patients evaluated for acute respiratory illness at hospitals in the Seattle metropolitan area were screened for a panel of respiratory viruses. Transmission models were fit to each virus to estimate the magnitude reduction in transmission due to weather-related disruptions. Changes in contact rates and care-seeking were informed by data on local traffic volumes and hospital visits. RESULTS: Disruption in contact patterns reduced effective contact rates during the intervention period by 16 to 95%, and cumulative disease incidence through the remainder of the season by 3 to 9%. Incidence reductions were greatest for viruses that were peaking when the disruption occurred and least for viruses in an early epidemic phase. CONCLUSION: High-intensity, short-duration social distancing measures may substantially reduce total incidence in a respiratory virus epidemic if implemented near the epidemic peak. For SARS-CoV-2, this suggests that, even when SARS-CoV-2 spread is out of control, implementing short-term disruptions can prevent COVID-19 deaths.


Subject(s)
Epidemics/prevention & control , Physical Distancing , Respiratory Tract Infections/transmission , Respiratory Tract Infections/virology , Weather , COVID-19 , Cities , Humans , Incidence , Models, Theoretical , Retrospective Studies , Washington
SELECTION OF CITATIONS
SEARCH DETAIL