Distinct features of influenza and COVID-19
| Influenza | COVID-19 | |
|---|---|---|
| Seasonality | Fall-winter | Year-round |
| Annual incidence | ||
| Overall | 8% (3% –11%) | 6%–8% |
| Children | 20% (unvaccinated) | Not applicable (no vaccine) |
| Adults | 10% (unvaccinated) | 6%–8% (unvaccinated) |
| Age distribution | Children > adults | Adults > children |
| Incubation period (days) | 1 –4 days | 2– 14 days |
| Duration of infectivity | 1 day before to 7 days after onset of illness | 2 days before to 10 (20 for severe cases) days after onset of illness |
| Onset of symptoms | More acute | More subacute |
| Super-spreaders (1 person infects 8 persons) | Not reported | 1% |
| Typical or characteristic features at onset of illness | Fever, headache, dry cough | Loss of sense of taste or smell |
| Severity of illness | ||
| Asymptomatic | 5%–50% | 30%–40% |
| Symptomatic | ||
| Mild | 98% | 80% |
| Moderate | 1%–2% | 15% |
| Severe | 0.2% | 5% |
| Fatal | 0.04%–0.1% | 3%–4% |
| Duration of acute illness | 5–7 days | 2– 6 weeks |
| Incidence of long-term symptoms lasting longer than 4 weeks | Clinically silent viral shedding for weeks to months in immunocompromised individuals | 60%–70% regardless of viral shedding |
| Complications | Pneumonia | Deep venous thrombosis and pulmonary embolism |
| Exacerbation of underlying chronic heart and lung diseases | Multisystem inflammatory disorders | |
Data from references 11 and 12.