. 2020 Mar 28;26(6):729–734. doi: 10.1016/j.cmi.2020.03.026

Table 3.

Facts and open issues about COVID-19

Facts about COVID-19	Questions needing further assessment
• SARS-CoV-2 is more phylogenetically related to SARS-CoV than to MERS-CoV • Only minor differences have been found between the genome sequences of SARS-CoV-2 and SARS-CoV • SARS-CoV-2 affinity for angiotensin-converting enzyme 2 (ACE2) receptor is higher than that of SARS-CoV • COVID-19 fatality rate is lower than that found in SARS and MERS • SARS-CoV-2 RNA has been detected in the stools of infected patients, similarly to SARS-CoV and MERS-CoV • 1.2% of COVID-19 cases are asymptomatic • COVID-19 is not very different from SARS and MERS regarding demographic characteristics, laboratory and radiological findings • Clinical complications in COVID-19 are as frequent as in SARS, but less frequent than in MERS • Viral loads in COVID-19 patients are higher at the time of symptom onset and progressively decrease during the clinical course of the disease	• What is the role of amino acid substitutions on the SARS-CoV-2 receptor binding domain in terms of pathogenesis? • Does the higher affinity of SARS-CoV-2 than SARS-CoV for angiotensin-converting enzyme 2 (ACE2) receptor have an implication in respiratory complications? • Is the faecal–oral route of transmission possible for COVID-19? • What is the role of asymptomatic COVID-19 cases in the epidemiology of the disease? • What is the actual COVID-19 basic reproductive number (R₀)? • Are differences in viral kinetics in the respiratory tract responsible for the different spreading potential of COVID-19, SARS and MERS?

Facts about COVID-19

Questions needing further assessment

•
SARS-CoV-2 is more phylogenetically related to SARS-CoV than to MERS-CoV
•
Only minor differences have been found between the genome sequences of SARS-CoV-2 and SARS-CoV
•
SARS-CoV-2 affinity for angiotensin-converting enzyme 2 (ACE2) receptor is higher than that of SARS-CoV
•
COVID-19 fatality rate is lower than that found in SARS and MERS
•
SARS-CoV-2 RNA has been detected in the stools of infected patients, similarly to SARS-CoV and MERS-CoV
•
1.2% of COVID-19 cases are asymptomatic
•
COVID-19 is not very different from SARS and MERS regarding demographic characteristics, laboratory and radiological findings
•
Clinical complications in COVID-19 are as frequent as in SARS, but less frequent than in MERS
•
Viral loads in COVID-19 patients are higher at the time of symptom onset and progressively decrease during the clinical course of the disease

•
What is the role of amino acid substitutions on the SARS-CoV-2 receptor binding domain in terms of pathogenesis?
•
Does the higher affinity of SARS-CoV-2 than SARS-CoV for angiotensin-converting enzyme 2 (ACE2) receptor have an implication in respiratory complications?
•
Is the faecal–oral route of transmission possible for COVID-19?
•
What is the role of asymptomatic COVID-19 cases in the epidemiology of the disease?
•
What is the actual COVID-19 basic reproductive number (R₀)?
•
Are differences in viral kinetics in the respiratory tract responsible for the different spreading potential of COVID-19, SARS and MERS?