development
  
 

    

          
    
    

      

        
      


      
      
        
        
                  

            Period. 6 – 12 April 2020          

                
       
    


    
    
    

    
          
High Contagiousness and Rapid Spread of Severe Acute Respiratory Syndrome Coronavirus 2


Sanche et al, Emerging Infectious Disease EARLY RELEASE, 7 April 2020


https://wwwnc.cdc.gov/eid/article/26/7/20-0282_article


Findings


Initial estimates of the early dynamics of the outbreak in Wuhan suggest a doubling time of 2.3–3.3 days, which is less than half the time of prior estimates (6-7 days). Assuming a serial interval of 6–9 days, the authors also calculate a median basic reproductive number (R0) of 5.7 (95% CI 3.8–8.9) in the early stages of the pandemic, which is more than double existing estimates for R0 (2.2-2.7). Based on modelling of high-resolution domestic travel and infection data, the paper also shows that active surveillance, contact tracing, quarantine, and early strong social distancing efforts can slow transmission.


Interpretation


Dynamics of transmission for COVID-19 is not uniform and can be significantly higher in the early stages than previously thought.


Facemasks and similar barriers to prevent respiratory illness such as COVID-19: A rapid systematic review


Brainard et al, 6 April 2020, NOT YET PEER REVIEWED


https://www.medrxiv.org/content/10.1101/2020.04.01.20049528v1


Findings


Based on a review of 31 studies (including 12 RCTs), the authors conclude that wearing face masks can be slightly protective against primary infection from casual community contact, and modestly protective against household infections when both infected and uninfected members wear face masks. Randomized Control Trials often suffered from poor compliance and controls using face masks, resulting in under-estimation of the protective effect, while observational studies exaggerated their efficacy.


Interpretation


The authors conclude that while the evidence is insufficient to support widespread use of face masks as a protective measure against COVID-19, there is enough evidence to support their use for short periods, especially vulnerable individuals and in transient high-risk environments.


Respiratory virus shedding in exhaled breath and efficacy of face masks


Leung et al, Nature Medicine, 3 April 2020


https://www.nature.com/articles/s41591-020-0843-2


Findings


Surgical face masks have been shown to effectively block the spread of seasonal coronaviruses in respiratory droplets, suggesting that masks can prevent transmission of COVID-19, which has been detected in both ‘coarse’ droplets and finer ‘aerosol’ droplets emitted by volunteers not wearing masks. Larger ‘coarse’ particles are carried by sneezes and coughs, whereas exhaled breath can spread ‘aerosol’ droplets, which have a diameter of five micrometres or less. Masks reduced detection of viral RNA in both types of droplets.


Interpretation


Face masks could prevent transmission of the novel coronaviruses and influenza viruses from symptomatic individuals.



    
     
      
      
      
            
      
              

        

          
This development is part of the digest;