Table 7

Knowns, uncertainties and unknowns about COVID-19, as of May 2020

FactorAvailable information
Disease spectrum
  • Many different estimates:

  • Initially, it was estimated that among infected, 30% remained asymptomatic, 55%–80% had mild/moderate disease, 10%–14% had severe disease, and 5%–6% became critically ill.73 90–92

  • Very variable estimates for remaining totally asymptomatic (estimated 5%–80%93–96).

  • What determines that an infection remains asymptomatic?

  • Quasi-absence of disease in children: why?

Case fatality rate (CFR)
  • Initial estimates CFR: 2%–3%; comparisons: influenza 0.1%; common cold: 0%; SARS: 9%–10%; MERS: 30%.97

  • Calculated infection fatality rates (cIFR) and calculated CFR (cCFR) on the Princess Diamond were 1.3% and 2.6%, respectively (for all ages combined), and projected cIFR and cCFR for China were between 0.6%–0.66% and 1.2%–1.38%, respectively.90 98 In Gangelt, Germany: cCFR of 0.37%.99

  • CFR is influenced significantly by age; male sex; comorbidities; body mass index and/or fitness; and adequacy of supportive treatment, mainly oxygen therapy.100 101 Also, as in certain other viral diseases such as measles, possibly influenced by the dose of virus in initial infectious inoculum (see Box 3).

  • CFR and IFR vary depending on population distribution. March 2020, estimated IFR UK: 0.9%, Italy: 1.14%–6.22% initial estimate which increased to 9.26%, Spain: 6.16%, France: 4.21%.102 103

Medication/treatment options
  • Treatments being used: hydroxychloroquine and chloroquine, remdesivir, azithromycin, convalescent plasma and other antivirals.

  • At the time of writing (May 2020), no proven effective treatment. Many clinical trials ongoing.

  • Oxygen therapy most essential component of case management. Low oxygen saturation a dominant feature of COVID-19, curiously dissociated from dyspnoea. In most cases, oxygen can be administered through a facial mask. In very advanced disease, oxygen administered through artificial ventilation, requiring sophisticated equipment and highly skilled personnel.