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PubMed; 2020.
Preprint in English | PubMed | ID: ppcovidwho-333501


The role of asymptomatic carriers in transmission poses challenges for control of the COVID-19 pandemic. Study of asymptomatic transmission and implications for surveillance and disease burden are ongoing, but there has been little study of the implications of asymptomatic transmission on dynamics of disease. We use a mathematical framework to evaluate expected effects of asymptomatic transmission on the basic reproduction number R0 (i.e., the expected number of secondary cases generated by an average primary case in a fully susceptible population) and the fraction of new secondary cases attributable to asymptomatic individuals. If the generation-interval distribution of asymptomatic transmission differs from that of symptomatic transmission, then estimates of the basic reproduction number which do not explicitly account for asymptomatic cases may be systematically biased. Specifically, if asymptomatic cases have a shorter generation interval than symptomatic cases, R0 will be over-estimated, and if they have a longer generation interval, R0 will be under-estimated. Estimates of the realized proportion of asymptomatic transmission during the exponential phase also depend on asymptomatic generation intervals. Our analysis shows that understanding the temporal course of asymptomatic transmission can be important for assessing the importance of this route of transmission, and for disease dynamics. This provides an additional motivation for investigating both the importance and relative duration of asymptomatic transmission.

Open Forum Infectious Diseases ; (2328-8957 (Electronic))2020.
Article in English | PMC | ID: covidwho-851859


Background: There are few data about long-term respiratory complications following Middle East Respiratory Syndrome coronavirus (MERS-CoV) infection. This study aimed to evaluate respiratory functions and radiologic sequelae according to the severity of infection one year after the patients experienced MERS-CoV infection. Methods: A total of 73 patients undergoing MERS-CoV infection during the 2015 MERS outbreak in South Korea were enrolled in this prospective multicenter study. Pulmonary function tests and 6-minute walking tests were performed 1 year after infection. Radiologic sequelae was defined as fibrosis or atelectasis on chest computer tomography and severe pneumonia was defined as that requiring oxygen therapy. Multivariate linear regression tests were used to evaluate the effect of infection severity on respiratory function. Results: At the time of MERS-CoV infection, 18 patients had no pneumonia, 35 experienced mild pneumonia, and 20 did severe pneumonia. The median age was not different between groups (P = 0.942). Forced vital capacity (FVC) was 102.6%, 94.9%, and 88.7% in the no, mild, and severe pneumonia group, respectively (P = 0.010) and forced expiratory volume in 1 second was 105.3%, 95.7%, and 91.7% (P = 0.057). Diffusing capacity (DLCO) was significantly lower in the severe pneumonia group than in the no or mild pneumonia group (78.3% vs. 89.4% or 88.6%, P = 0.035). In multivariate analyses, FVC and DLCO were significantly correlated with infection severity after adjustment with age, sex, underlying lung disease, and smoking. There was no difference in the walking distance of 6 minute tests between groups. Radiologic sequelae were shown in 18.8%, 65.6%, and 100% in the no, mild, and severe pneumonia group, respectively (P < 0.001). Conclusion: The patients with more severe pneumonia by MERS-CoV had more impaired respiratory function in one year follow-up, which was compatible with radiologic sequelae. Disclosures: All authors: No reported disclosures. FAU - Il Jun, Kang