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Molecular mechanisms and epidemiology of #COVID_19 from an allergist’s perspective

FIG 1. A, Structure of RBD of spike protein S1 of SARS-CoV-2 bound to ACE2. Structure of ACE2 bound tothe RBD of the S1 spike protein of SARS-CoV-2.94-96The chimeric RBD is in orange, and human ACE2 is ingreen. The figure was created with Research Collaboratory for Structural Bioinformatics Protein Data Bank(, RBD of S1 spike protein of SARS-CoV-2.B,Cartoon showing how SARS-CoV-2binds to the lung epithelial cells. SARS-CoV-2 has a spike protein with transmembrane (TM), S1 and S2 part.S1 part has an RBD. The virion uses the spike protein S1 to attach with RBD of the host ACE2 receptor on thecell membrane with the help of the cellular TMPRSS2. Following attachment of S1 to ACE2, the host serineprotease TMPRSS2 cleaves the S2 protein from S1, and plays a role in membrane fusion of CoVs. The figurewas created using BioRender (,The prevalence of asthma in patients hospitalizedfor COVID-19 in United States. Data were extracted from April 8, 2020, MMWR report37and Centers for Dis-ease Control and Prevention.97The total length of each bar represents the prevalence rates of COVID-19 ineach age group. The length of the blue part of this bar is the expected prevalence rate of asthma in each agegroup. The orange part represents the prevalence rate of COVID-19 in excess of the expected prevalence rateof asthma in each age group.

Several factors likely contribute to the efficient transmission of #SARS_CoV_2. The receptor-binding domain of SARS-CoV-2 has a 10- to 20-fold higher receptor-binding capacity compared with previous pandemic coronaviruses. In addition, because asymptomatic persons infected with SARS-CoV-2 have high viral loads in their nasal secretions, they can silently and efficiently spread the disease. PCR-based tests have emerged as the criterion standard for the diagnosis of infection. Caution must be exercised in interpreting antibody-based tests because they have not yet been validated, and may give a false sense of security of being “immune” to SARS-CoV-2.

We discuss how the development of some symptoms in #allergic_rhinitis can serve as clues for new-onset COVID-19. There are mixed reports that #asthma is a risk factor for severe COVID-19, possibly due to differences in asthma endotypes. The rapid spread of COVID-19 has focused the efforts of scientists on repurposing existing Food and Drug Administration–approved drugs that inhibit viral entry, endocytosis, genome assembly, translation, and replication.

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