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Arquivo Diário 18 de fevereiro de 2021

18

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Transmissão por SARS-CoV-2 por aerossóis respiratórios exige ênfase na ventilação e uso por tod@s de máscaras bem adaptadas

Por Rede APS

No início da pandemia causada pelo SARS-CoV-2 eram reconhecidos como mecanismos de transmissão do vírus: o contato direto ou próximo com uma pessoa infectada (a menos de um ou dois metros), e o contato com superfícies. No entanto, a evidencia científica disponível atualmente indica que a transmissão através de superfícies não é tão importante quanto as gotículas exaladas quando se tosse, espirra, fala, respira, e a inalação de aerossóis respiratórios (Morawska L, Cao J. 2020- Tang S, Mao Y, Jones RM, et al. 2020). Conforme essas novas evidências é necessário adaptar os protocolos de biossegurança já desenhados.

Estudos de laboratório publicados em março de 2020 mostraram que o vírus SARS-CoV-2 pode permanecer em materiais plásticos ou de aço inoxidável durante vários dias. Com base nesses resultados concluiu-se que o SARS-CoV-2 poderia ser transmitido através de superfícies inanimadas. Isso ocasionou que a OMS e as autoridades sanitárias dos diferentes países recomendassem a desinfecção de superfícies que tocamos com frequência e alimentos. No entanto, Goldman, um microbiólogo da Faculdade de Medicina de Rutgers New Jersey em Newark analisou os estudos e concluiu que existia pouca evidência que indicasse que o SARS-CoV-2 poderia ser transmitido para outras pessoas através do contato com superfícies contaminadas. O pesquisador indicou que as condições em que estudos anteriores haviam sido desenvolvidos em laboratório, utilizando cargas virais muito altas, não correspondiam com o que acontecia na vida real. Num comentário enviado à Revista The Lancet em julho de 2020, Goldman apontou que risco de transmissão a través de superfícies inanimadas é pequeno, podendo acontecer somente nos casos em que uma pessoa infectada tosse ou espirra na superfície e outra pessoa toca essa superfície pouco tempo depois (1-2h) (Goldman, 2020), como pode ocorrer em um serviço de saúde. Outros pesquisadores chegaram a conclusões similares, a transmissão através de superfícies inanimadas é possível, mas parece ser uma forma pouco comum de contágio (Lewis D. 2020). Isso também poderia explicar por que numa comparação global, durante os primeiros meses da pandemia, a limpeza e desinfecção de superfícies foi uma das intervenções de menor sucesso para o controle da disseminação do vírus (Haug, N. et al., 2020).

Por outro lado, Tang S, Mao Y, Jones RM, et al. (2020) revisaram a evidência disponível de pesquisas empíricas e de laboratório (até 30 de julho de 2020) e encontraram que vários estudos respaldam que a transmissão por aerossóis do SARS-CoV-2 é plausível. Durante a exalação, a fala ou a tosse são produzidas microgotas respiratórias (aerossóis), nas quais o vírus pode sobreviver durante um tempo relativamente amplo em condições favoráveis. Esses aerossóis podem potencialmente viajar no ar e transportar o vírus dezenas de metros mais longe do que as gotas maiores (que alcançam no máximo dois metros) (Morawska L, Cao J. 2020; Tang S, Mao Y, Jones RM, et al. 2020)

 

Fonte: Morawska L, Cao J. 2020

Alguns estudos analisaram casos de surtos do vírus SARS-CoV-2 (em um restaurante em Guangzhou (China), em um coro em Mount Vernon EE. UU, entre outros) e concluíram que a alta taxa de infecção somente pode ter sido possível considerando como principal via de contágio a inalação de microgotas contaminadas no ar (aerossóis) (Miller SL, Nazaroff WW, Jimenez JL, et al, 2020; Buonanno G, Morawska L, Stabile L, 2020).

As pesquisas também apontam que o contágio por inalação de aerossóis respiratórios depende das condições do meio ambiente, como ventilação, lotação e tempo de exposição (Miller SL, Nazaroff WW, Jimenez JL, et al, 2020; Buonanno G, Morawska L, Stabile L, 2020; Tang S, Mao Y, Jones RM, et al. 2020; Morawska L, Milton DK. 2020).

Atualmente pesquisadores concordam que a transmissão por inalação de aerossóis respiratórios é muito importante e que o risco de contágio através de superfícies e fômites é baixo. Portanto, pesquisadoras como Lewis D. (2020) têm sugerido que o tempo e recursos investidos na desinfecção excessiva de superfícies e alimentos, podem ser melhor investidos melhorando a ventilação e limpando o ar contaminado.

Conforme essas novas evidências, para diminuir eficazmente a transmissão do SARS-CoV-2 é necessário além das medidas já implementadas (higiene de mãos, uso de máscaras, distanciamento e isolamento social, evitar aglomerações) fazer investimentos para garantir uma adequada e suficiente ventilação dos locais. Os pesquisadores sugerem que para melhorar a ventilação em interiores podem ser implementados mecanismos naturais (aberturas para ventilação, abrir portas e janelas) ou mecânicos (uso de sistemas de filtração do ar exterior, modificação de sistemas de ventilação criando salas de isolamento com pressão negativa, evitar a recirculação de ar em sistemas de ventilação, uso de irradiação germicida ultravioleta em locais onde não é possível evitar a recirculação do ar, limpadores de ar portátil). (Morawska L, Tang JW, Bahnfleth W, et al. 2020).

Fonte: Morawska L, Tang JW, Bahnfleth W, et al. 2020

É preciso que as autoridades nacionais dos diferentes países, Ministério da Saúde e os gestores reconheçam a importância desse mecanismo de transmissão do vírus e implementem intervenções para diminuir o contágio por esta via. A implementação de intervenções para melhorar a ventilação, como as mencionadas, é muito importante em unidades de Atenção Primária, hospitais, escolas, restaurantes, locais de trabalho, supermercados, transporte público e outros locais fechados.

Para a APS, este conhecimento deve orientar estratégias de comunicação e de ação comunitária para promover a redução do risco de contágio e incentivar cotidianamente o uso de máscaras de forma correta, bem ajustadas ao rosto, cobrindo nariz, boca e queixo, para conter o contágio por aerossóis.

O reconhecimento da transmissão respiratória como principal forma de contágio além da necessidade de promover a ventilação dos ambientes, exige intensificar a promoção do uso de máscaras por todos e todas.

Usar uma máscara –  qualquer máscara – reduz o risco de infecção com o coronavírus, mas usar uma máscara cirúrgica bem ajustada ou colocar uma máscara de pano em cima de uma máscara cirúrgica pode aumentar muito a proteção para o usuário e os outros, relata estudo dos Centros de Controle de Doenças e Prevenção (CDC) dos EUA. Uma nova pesquisa da agência mostra que a transmissão do vírus pode ser reduzida em até 96,5% se um indivíduo infectado e um indivíduo não infectado usarem máscaras cirúrgicas bem ajustadas ou uma combinação de pano e máscara cirúrgica. Consulte as recomendações do CDC/ US DHHS em https://www.cdc.gov/mmwr/volumes/70/wr/pdfs/mm7007e1-H.pdf

Por: Diana Ruiz, doutoranda que contribui com a Rede APS

Maiores informações podem ser acessadas nos artigos científicos consultados para construir este boletim, disponíveis também na biblioteca do Site da Rede APS:

Buonanno G, Morawska L, Stabile L. Quantitative assessment of the risk of airborne transmission of SARS-CoV-2 infection: perspective and retrospective applications. medRxiv 2020; Disponível em: https://www.sciencedirect.com/science/article/pii/S0160412020320675.  Acesso 10 jan 2021.

Goldman, E. Exaggerated risk of transmission of COVID-19 by fomites Lancet Infect. Dis. 20 , 892–893 (2020). Disponível em: https://www.thelancet.com/journals/laninf/article/PIIS1473-3099(20)30561-2/fulltext. Acesso 10 jan 2021

Haug, N. et al. Ranking the effectiveness of worldwide COVID-19 government interventions Nature Human Behav. 4, 1303–1312 (2020). Disponível em: https://www.nature.com/articles/s41562-020-01009-0 Acesso 10 jan 2021

Lewis D. 2021. COVID-19 rarely spreads through surfaces. So why are we still deep cleaning? Nature 590, 26–28 https://doi.org/10.1038/d41586-021-00251-4

Miller SL, Nazaroff WW, Jimenez JL, et al.  Transmission of SARS-CoV-2 by inhalation of respiratory aerosol in the Skagit Valley Chorale superspreading event. medRxiv 2020;Disonível em:  https://www.medrxiv.org/content/10.1101/2020.06.15.20132027v2 Acesso 12 jan 2021.

Morawska L, Cao J. 2020. Airborne transmission of SARS-CoV-2: The world should face the reality. Environment International 139:105730. https://doi.org/https://doi.org/10.1016/j.envint.2020.105730 Acesso 12 jan 2021

Morawska L, Milton DK. 2020. It Is Time to Address Airborne Transmission of Coronavirus Disease 2019 (COVID-19). Clinical infectious diseases : an official publication of the Infectious Diseases Society of America 71:2311–2313. https://doi.org/10.1093/cid/ciaa939 Acesso 11 jan 2021

Morawska L, Tang JW, Bahnfleth W, et al. 2020. How can airborne transmission of COVID-19 indoors be minimised? Environment International 142:105832. https://doi.org/https://doi.org/10.1016/j.envint.2020.105832 Acesso 11 jan 2021

Tang S, Mao Y, Jones RM, et al. 2020. Aerosol transmission of SARS-CoV-2? Evidence, prevention and control. Environment International 144:. https://doi.org/10.1016/j.envint.2020.106039 Acesso 11 jan 2021

Brooks, Beezhold, Noti, et al. Maximizing Fit for Cloth and Medical Procedure Masks to Improve Performance and Reduce SARS-CoV-2 Transmission and Exposure, 2021. Center for Disease Control and Prevention. 10 fev 2021 https://www.cdc.gov/mmwr/volumes/70/wr/pdfs/mm7007e1-H.pdf  Acesso 11 jan 2021

 

Aerosol transmission of SARS-CoV-2? Evidence, prevention and control

Por Rede APS

As public health teams respond to the pandemic of coronavirus disease 2019 (COVID-19), containment and understanding of the modes of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) transmission is of utmost importance for policy making. During this time, governmental agencies have been instructing the community on handwashing and physical distancing measures. However, there is no agreement on the role of aerosol transmission for SARS-CoV-2. To this end, we aimed to review the evidence of aerosol transmission of SARS-CoV-2. Several studies support that aerosol transmission of SARS-CoV-2 is plausible, and the plausibility score (weight of combined evidence) is 8 out of 9. Precautionary control strategies should consider aerosol transmission for effective mitigation of SARS-CoV-2.

Article – Tang, Mao, Jones, 2020. Aerosol transmission of SARS-CoV-2 Evidence, prevention and control

How can airborne transmission of COVID-19 indoors be minimised?

Por Rede APS

During the rapid rise in COVID-19 illnesses and deaths globally, and notwithstanding recommended precautions, questions are voiced about routes of transmission for this pandemic disease. Inhaling small airborne droplets is probable as a third route of infection, in addition to more widely recognized transmission via larger respiratory droplets and direct contact with infected people or contaminated surfaces. While uncertainties remain regarding the relative contributions of the different transmission pathways, we argue that existing evidence is sufficiently strong to warrant engineering controls targeting airborne transmission as part of an overall strategy to limit infection risk indoors. Appropriate building engineering controls include sufficient and effective ventilation, possibly enhanced by particle filtration and air disinfection, avoiding air recirculation and avoiding overcrowding. Often, such measures can be easily implemented and without much cost, but if only they are recognised as significant in contributing to infection control goals. We believe that the use of engineering controls in public buildings, including hospitals, shops, offices, schools, kindergartens, libraries, restaurants, cruise ships, elevators, conference rooms or public transport, in parallel with effective application of other controls (including isolation and quarantine, social dis- tancing and hand hygiene), would be an additional important measure globally to reduce the likelihood of trans- mission and thereby protect healthcare workers, patients and the general public.

Article – Morawska, Tang Bahnfleth 2020 How can airborne transmission of COVID-19 indoors be minimised

Airborne transmission of SARS-CoV-2: The world should face the reality

Por Rede APS

Hand washing and maintaining social distance are the main measures recommended by the World Health Organization (WHO) to avoid contracting COVID-19. Unfortunately, these measured do not prevent infection by inhalation of small droplets exhaled by an infected person that can travel distance of meters or tens of meters in the air and carry their viral content. Science explains the mechanisms of such transport and there is evidence that this is a significant route of infection in indoor environments. Despite this, no countries or authorities consider airborne spread of COVID-19 in their regulations to prevent infections transmission indoors. It is therefore extremely important, that the national authorities acknowledge the reality that the virus spreads through air, and recommend that adequate control measures be implemented to prevent further spread of the SARS-CoV-2 virus, in particularly removal of the virus-laden droplets from indoor air by ventilation.

Article – Morawska, Cao. 2020 Airborne transmission of SARS-CoV-2 The world should face the reality

Transmission of SARS-CoV-2 by inhalation of respiratory aerosol in the Skagit Valley Chorale superspreading event

Por Rede APS

During the 2020 COVID-19 pandemic, an outbreak occurred following attendance of a symptomatic index case at a regular weekly rehearsal on 10 March of the Skagit Valley Chorale (SVC). After that rehearsal, 53 members of the SVC among 61 in attendance were confirmed or strongly suspected to have contracted COVID-19 and two died. Transmission by the airborne route is likely. It is vital to identify features of cases such as this so as to better understand the factors that promote superspreading events. Based on a conditional assumption that transmission during this outbreak was by inhalation of respiratory aerosol, we use the available evidence to infer the emission rate of airborne infectious quanta from the primary source. We also explore how the risk of infection would vary with several influential factors: the rates of removal of respiratory aerosol by ventilation; deposition onto surfaces; and viral decay. The results indicate an emission rate of the order of a thousand quanta per hour (mean [interquartile range] for this event = 970 [680-1190] quanta per hour) and demonstrate that the risk of infection is modulated by ventilation conditions, occupant density, and duration of shared presence with an infectious individual.

Keywords: aerosol transmission, infectious disease, ventilation, virus, pandemic, risk.

Article – Miller, Nazaroff, Jimenez et al. 2020 Transmission of SARS-CoV-2 by inhalation of respiratory aerosol in the Skagit Valley Chorale superspreading even

Ranking the effectiveness of worldwide COVID-19 government interventions

Por Rede APS

Assessing the effectiveness of non-pharmaceutical interventions (NPIs) to mitigate the spread of SARS-CoV-2 is critical to inform future preparedness response plans. Here we quantify the impact of 6,068 hierarchically coded NPIs implemented in 79 territories on the effective reproduction number, Rt, of COVID-19. We propose a modelling approach that combines four com- putational techniques merging statistical, inference and artificial intelligence tools. We validate our findings with two exter- nal datasets recording 42,151 additional NPIs from 226 countries. Our results indicate that a suitable combination of NPIs is necessary to curb the spread of the virus. Less disruptive and costly NPIs can be as effective as more intrusive, drastic, ones (for example, a national lockdown). Using country-specific ‘what-if’ scenarios, we assess how the effectiveness of NPIs depends on the local context such as timing of their adoption, opening the way for forecasting the effectiveness of future interventions.

Article – Haug et al Ranking the effectiveness of worldwide COVID-19 government interventions Nature Human 2020

Exaggerated risk of transmission of COVID-19 by fomites

Por Rede APS

Availability of diagnostics and antifungals, and training in their use, will reduce deaths from advanced HIV disease (by up to 30%).2 Mistaken diagnoses of pulmonary tuberculosis when actually the problem is a fungal lung infection will be averted. Implementation of these priorities will strengthen public health systems, support antimicrobial stewardship,9 develop clinician skills, and appropriately diversify differential diagnosis. New approaches have to be explored, such as the implementation of artificial intelligence, to address the shortage of health-care workers in the Latin American and Caribbean region, Africa, and southeast Asia. We anticipate that the enhancement, innovation, and increased integration of fungal disease diagnosis and management within the health system will benefit not only those with fungal disease, but also improve the effectiveness, efficiency, and quality of the entire health- care system.

Article – Goldman, 2020 Exaggerated risk of transmission of COVID-19 by fomites

Quantitative assessment of the risk of airborne transmission of SARS-CoV-2 infection: Prospective and retrospective applications

Por Rede APS

Airborne transmission is a recognized pathway of contagion; however, it is rarely quantitatively evaluated. The numerous outbreaks that have occurred during the SARS-CoV-2 pandemic are putting a demand on researchers to develop approaches capable of both predicting contagion in closed environments (predictive assessment) and analyzing previous infections (retrospective assessment).

This study presents a novel approach for quantitative assessment of the individual infection risk of susceptible subjects exposed in indoor microenvironments in the presence of an asymptomatic infected SARS-CoV-2 subject. The application of a Monte Carlo method allowed the risk for an exposed healthy subject to be evaluated or, starting from an acceptable risk, the maximum exposure time. We applied the proposed approach to four distinct scenarios for a prospective assessment, highlighting that, in order to guarantee an acceptable risk of 10− 3 for exposed subjects in naturally ventilated indoor environments, the exposure time could be well below one hour. Such maximum exposure time clearly depends on the viral load emission of the infected subject and on the exposure conditions; thus, longer exposure times were estimated for mechanically ventilated indoor environ- ments and lower viral load emissions. The proposed approach was used for retrospective assessment of docu- mented outbreaks in a restaurant in Guangzhou (China) and at a choir rehearsal in Mount Vernon (USA), showing that, in both cases, the high attack rate values can be justified only assuming the airborne transmission as the main route of contagion. Moreover, we show that such outbreaks are not caused by the rare presence of a superspreader, but can be likely explained by the co-existence of conditions, including emission and exposure parameters, leading to a highly probable event, which can be defined as a “superspreading event”.

Article – Bounanno, Morawska, Stabile 2020 Quantitative assessment of the risk of airborne transmission of SARS-CoV-2 infection perspective and retrospective applications