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Virüslerin, özellikle de koronavirüsler gibi RNA virüslerinin çoğalması ve yayılması sırasında genomlarında mutasyonlar gelişir. Mutasyonların çoğunun anlamlı bir etkisi olmamakla birlikte, bazı mutasyonlar bulaştırıcılığın artması gibi virüse avantajlar sağlayabilir. Bu şekilde avantajlı hale gelen virüs varyantlarının seçilmesi ve baskın hale gelmesi kolaylaşabilir. SARS-CoV-2 mutasyonlarının dünyada yayılmakta olduğu ve küresel bir tehdit oluşturduğu görülmektedir. Bu nedenlerle, risk oluşturan mutasyonlara yönelik genomik sürveyans ağları oluşturularak mevcut ve ortaya çıkabilecek yeni varyantların izi sürülmeli (moleküler sürveyans) ve yayılmalarını engellemek için uygulanmakta olan önlemler sıkılaştırılmalı; yeni varyantların fenotipik özelliklerinin gerekli kılacağı ek önlemler alınmalıdır.
Şu ana kadar üç varyantın (B.1.1.7, B.1.351, P.1) bulaşma hızlarının artmış ve mevcut epidemiyolojik durumda değişikliklere neden olması nedeniyle risk oluşturduğu kabul edilmektedir. Üç varyant da SARS-CoV-2’nin evrimleşme hızından beklenenin ötesinde mutasyon biriktirmiş olmaları ile de dikkat çekmektedir.

Derek K ChuElie A AklHolger J Schünemann

The Lancet Vol 395 June 27, 2020 Tam metin için tıklayınız

Summary
Background Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) causes COVID-19 and is spread personto-person through close contact. We aimed to investigate the effects of physical distance, face masks, and eye
protection on virus transmission in health-care and non-health-care (eg, community) settings.
Methods We did a systematic review and meta-analysis to investigate the optimum distance for avoiding person-toperson virus transmission and to assess the use of face masks and eye protection to prevent transmission of viruses.
We obtained data for SARS-CoV-2 and the betacoronaviruses that cause severe acute respiratory syndrome, and
Middle East respiratory syndrome from 21 standard WHO-specific and COVID-19-specific sources. We searched
these data sources from database inception to May 3, 2020, with no restriction by language, for comparative studies
and for contextual factors of acceptability, feasibility, resource use, and equity. We screened records, extracted data,
and assessed risk of bias in duplicate. We did frequentist and Bayesian meta-analyses and random-effects metaregressions. We rated the certainty of evidence according to Cochrane methods and the GRADE approach. This study
is registered with PROSPERO, CRD42020177047.
Findings Our search identified 172 observational studies across 16 countries and six continents, with no randomised
controlled trials and 44 relevant comparative studies in health-care and non-health-care settings (n=25697 patients).
Transmission of viruses was lower with physical distancing of 1 m or more, compared with a distance of less than 1 m
(n=10736, pooled adjusted odds ratio [aOR] 0·18, 95% CI 0·09 to 0·38; risk difference [RD] –10·2%, 95% CI
–11·5 to –7·5; moderate certainty); protection was increased as distance was lengthened (change in relative risk
[RR] 2·02 per m; pinteraction=0·041; moderate certainty). Face mask use could result in a large reduction in risk of
infection (n=2647; aOR 0·15, 95% CI 0·07 to 0·34, RD –14·3%, –15·9 to –10·7; low certainty), with stronger
associations with N95 or similar respirators compared with disposable surgical masks or similar (eg, reusable
12–16-layer cotton masks; pinteraction=0·090; posterior probability >95%, low certainty). Eye protection also was associated
with less infection (n=3713; aOR 0·22, 95% CI 0·12 to 0·39, RD –10·6%, 95% CI –12·5 to –7·7; low certainty).
Unadjusted studies and subgroup and sensitivity analyses showed similar findings.
Interpretation The findings of this systematic review and meta-analysis support physical distancing of 1 m or more
and provide quantitative estimates for models and contact tracing to inform policy. Optimum use of face masks,
respirators, and eye protection in public and health-care settings should be informed by these findings and contextual
factors. Robust randomised trials are needed to better inform the evidence for these interventions, but this systematic
appraisal of currently best available evidence might inform interim guidance.

Allergy. 2020;75:1564–1581 Tam metin için tıklayınız

AZKUR et Al.

Abstract
As a zoonotic disease that has already spread globally to several million human beings and possibly to domestic and wild animals, eradication of coronavirus disease 2019 (COVID‐19) appears practically impossible. There is a pressing need to improve our understanding of the immunology of this disease to contain the pandemic by developing vaccines and medicines for the prevention and treatment of patients. In this review, we aim to improve our understanding on the immune response and immunopathological changes in patients linked to deteriorating clinical conditions such as cytokine storm, acute respiratory distress syndrome, autopsy findings and changes in acute‐phase reactants, and serum biochemistry in COVID‐19. Similar to many other viral infections, asymptomatic disease is present in a significant but currently unknown fraction of the affected individuals. In the majority of the patients, a 1‐week, self‐limiting viral respiratory disease typically occurs, which ends with the development of neutralizing antiviral T cell and antibody immunity. The IgM‐, IgA‐, and IgG‐type virus‐specific antibodies levels are important measurements to predict population immunity against this disease and whether cross‐reactivity with other coronaviruses is taking place. High viral load during the first infection and repeated exposure to virus especially in healthcare workers can be an important factor for severity of disease. It should be noted that many aspects of severe patients are unique to COVID‐19 and are rarely observed in other respiratory viral infections, such as severe lymphopenia and eosinopenia, extensive pneumonia and lung tissue damage, a cytokine storm leading to acute respiratory distress syndrome, and multiorgan failure. Lymphopenia causes a defect in antiviral and immune regulatory immunity. At the same time, a cytokine storm starts with extensive activation of cytokine‐secreting cells with innate and adaptive immune mechanisms both of which contribute to a poor prognosis. Elevated levels of acute‐phase reactants and lymphopenia are early predictors of high disease severity. Prevention of development to severe disease, cytokine storm, acute respiratory distress syndrome, and novel approaches to prevent their development will be main routes for future research areas. As we learn to live amidst the virus, understanding the immunology of the disease can assist in containing the pandemic and in developing vaccines and medicines to prevent and treat individual patients.