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Viral replication occurs early in the disease course and diminishes as the immune response takes over.1-3
Dysfunctional immune responses can lead to escalating inflammation and severe disease.2,3
ARDS: acute respiratory distress syndrome
CD: cluster of differentiation, CSF: cerebrospinal fluid, IL: interleukin, ICU: intensive care unit,
RANTES: regulated upon activation, normal T cell expressed and secreted, TNF: tumour necrosis factor
| NIH | IDSA | WHO* | |
|---|---|---|---|
| Asymptomatic or presymptomatic infection | No symptoms consistent with COVID-19 | ||
| Mild illness | Any COVID-19 signs and symptoms AND No shortness of breath, dyspnoea, or abnormal chest imaging |
SpO2 >94% on room air No supplemental oxygen required |
Symptomatic patients without evidence of viral pneumonia or hypoxia |
| Moderate illness | Evidence of lower respiratory disease by clinical assessment or imaging AND SpO2 ≥94% on room air at sea level |
Adolescent or adult with clinical signs of pneumonia but no signs of severe pneumonia, including SpO2 ≥90% on room air Child with clinical signs of pneumonia but no signs of severe pneumonia |
|
| Severe illness | SpO2 <94% on room air at sea level OR PaO2/FiO2<300 mm Hg OR Respiratory frequency >30 breaths/min OR Lung infiltrates >50% |
SpO2 ≤94% on room air, including patients on supplemental oxygen | Adolescent or adult with clinical signs of pneumonia plus one of the following: respiratory rate >30 breaths/min; SpO2 <90% on room air; or severe respiratory distress Child with clinical signs of pneumonia and at least one of the following: central cyanosis or SpO2 <90%; severe respiratory distress; general danger sign; inability to breastfeed or drink; lethargy or unconsciousness; or convulsions |
| Critical illness | Respiratory failure Septic shock AND/OR Multiple organ dysfunction |
Mechanical ventilation and ECMO End-organ dysfunction (ARDS) Sepsis/septic shock |
ARDS Sepsis Septic shock Acute thrombosis MIS-C |
* WHO classifications = mild disease, moderate disease, severe disease, critical disease.
ARDS: acute respiratory distress syndrome, ECMO: extracorporeal mechanical oxygenation, IDSA: Infectious Diseases Society of America, NIH: National Institutes of Health, MIS-C: multisystem inflammatory syndrome in children, PaO2/FiO2: ratio of arterial partial pressure of oxygen to fraction of inspired oxygen, SpO2: oxygen saturation, WHO: World Health Organization
80% of adult patients experience at least one long-term COVID-19 symptom after acute infection.12
The most common symptoms (reported in ≥24% of individuals in a published systematic review and meta-analysis) are:12
“Post COVID-19 condition” occurs in individuals with a history of probable or confirmed
SARS-CoV-2 infection, usually 3 months from the onset of COVID-19 with symptoms that last for at least 2 months and cannot be explained by an alternative diagnosis.13
Broad-spectrum manifestations include:14
Like with other viruses, recovered individuals can be reinfected with SARS-CoV-2,9 with a reported reinfection rate of 0.7%.15
Factors affecting the risk of reinfection include:9,15
View the WHO treatment guidelines
Find out more about how adaptive vaccines may help to combat recent variants
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