| Centers for Disease Control and Prevention | X Mayo Clinic X National Health Service UK• Coronavirus disease 2019 COVID-19 : Frequently asked questions | 
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| Social distancing against COVID-19: Implication for the control of influenza | Centers for Disease Control and Prevention | 
| Journal of Korean Medical Science | X Mayo Clinic X National Health Service UK• Marshall WF III expert opinion | 
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| Coronavirus disease 2019 COVID-19 : How COVID-19 spreads | X National Health Service UK• | 
Key facts about influenza flu.
| Centers for Disease Control and Prevention | Centers for Disease Control and Prevention | 
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| Allergic rhinitis: Clinical manifestations, epidemiology, and diagnosis |