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This is a clinician-written, evidence-based summary aligned to the 2026 MLA Content Map. It is intended for medical students and junior doctors preparing for the UKMLA. Always cross-reference with NICE guidance, local protocols, and clinical judgement.
Key points
- SARS-CoV-2: RNA betacoronavirus. Transmitted by respiratory droplets and aerosols. Incubation 2-14 days (typically 5-6 days)
- Spectrum: asymptomatic → mild (cough, fever, anosmia) → moderate (pneumonia) → severe (ARDS, multi-organ failure). Severity increases with age, obesity, immunosuppression, and comorbidity
- Key treatment: dexamethasone 6 mg OD for 10 days in hospitalised patients requiring oxygen or ventilation (RECOVERY trial — reduced mortality by ~1/3 in ventilated patients). Do NOT use in non-hypoxic patients
- Antivirals for high-risk patients: nirmatrelvir/ritonavir (Paxlovid) within 5 days of symptom onset — reduces hospitalisation in non-hospitalised high-risk adults
- Long COVID: symptoms persisting >12 weeks — fatigue, breathlessness, cognitive dysfunction ("brain fog"), palpitations. Managed supportively in specialist Long COVID clinics
Overview
COVID-19 is caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which emerged in Wuhan, China in late 2019 and caused a global pandemic. The virus binds to ACE2 receptors on host cells via the spike protein. Disease severity is determined by a combination of viral cytopathic effects and a dysregulated host immune response (cytokine storm) in the second week of illness. The RECOVERY trial, conducted in the UK, was instrumental in establishing dexamethasone as a life-saving treatment.
Epidemiology
COVID-19 has caused over 200,000 deaths in the UK. The pandemic phase ended following widespread vaccination and natural immunity, but SARS-CoV-2 continues to circulate as an endemic respiratory virus with seasonal waves. Vaccination remains the most effective prevention — UK programme offers boosters to high-risk groups. Mortality risk is highest in elderly, obese, immunocompromised, and those with diabetes, chronic lung/heart/kidney disease.
Clinical Features
Symptoms
Cough (new, continuous)
Fever (≥37.8°C)
Anosmia or ageusia (loss of smell/taste) — relatively specific for COVID-19
Fatigue, myalgia, headache
Sore throat, nasal congestion
Dyspnoea (typically day 5-10 — suggests viral pneumonia)
Diarrhoea, nausea (GI symptoms in ~10-20%)
Signs
Fever
Tachypnoea, hypoxia (SpO2 <94%) — may have "silent hypoxia" (hypoxia without proportionate dyspnoea)
Bilateral crackles (COVID pneumonia)
Signs of ARDS in critical illness
Investigations
First-line
SARS-CoV-2 PCR (nasopharyngeal swab)Gold standard for acute diagnosis — RT-PCR detects viral RNA. Can remain positive for weeks (does not necessarily indicate infectivity)
Lateral flow test (LFT/rapid antigen test)Point-of-care test — high specificity but lower sensitivity than PCR. Most useful in symptomatic individuals
Second-line
CXRBilateral peripheral ground-glass opacities and consolidation. Classic pattern: bilateral, lower zone predominant, peripheral
CT chestMore sensitive than CXR: bilateral ground-glass opacities, crazy paving pattern, peripheral/subpleural distribution. CTPA if PE suspected (COVID increases VTE risk)
BloodsRaised CRP, lymphopenia (characteristic), raised LDH, raised D-dimer, raised ferritin, raised IL-6 — all correlate with severity
Specialist
SARS-CoV-2 antibody testingIndicates previous infection or vaccination. Not used for acute diagnosis
CTPAIf pulmonary embolism suspected — COVID significantly increases VTE risk, especially in hospitalised patients
1
Mild disease (non-hospitalised)
- Self-care: rest, fluids, paracetamol for symptomatic relief
- Antivirals for HIGH-RISK non-hospitalised patients (within 5 days of symptom onset): nirmatrelvir/ritonavir (Paxlovid) — reduces hospitalisation risk
- High-risk: immunosuppressed, unvaccinated elderly, significant comorbidity
2
Hospitalised — requiring oxygen
- Dexamethasone 6 mg OD (oral or IV) for up to 10 days — RECOVERY trial evidence. Reduces mortality by ~1/3 in ventilated patients and ~1/5 in those on oxygen
- Do NOT give dexamethasone if NOT requiring oxygen — no benefit and potential harm
- Remdesivir: consider in hospitalised patients requiring supplemental oxygen (within 10 days of symptom onset)
- Tocilizumab (anti-IL-6): for rapidly deteriorating patients with high CRP and oxygen requirement — REMAP-CAP/RECOVERY evidence
3
Thromboprophylaxis
- All hospitalised COVID patients: prophylactic-dose LMWH (NICE NG191)
- COVID significantly increases VTE risk — maintain high index of suspicion for PE (D-dimer is often elevated; CTPA if clinical concern)
4
Critical care
- ARDS management: prone positioning (improves oxygenation), lung-protective ventilation, CPAP/high-flow nasal oxygen before intubation
- ECMO in refractory hypoxaemia in selected centres
5
Prevention — vaccination
- UK vaccination programme: primary course + boosters for high-risk groups (elderly, immunosuppressed, healthcare workers, carers)
- mRNA vaccines (Pfizer, Moderna) and protein subunit vaccines (Novavax) available
- Vaccination reduces severity, hospitalisation, and death — remains the most effective preventive measure
Complications
- ARDS: Most common cause of death in hospitalised COVID — bilateral pulmonary infiltrates, refractory hypoxia
- VTE: COVID-associated coagulopathy — PE, DVT. Significantly increased risk even after hospital discharge
- Myocarditis: Can cause troponin elevation and heart failure
- Long COVID: Symptoms persisting >12 weeks — fatigue, breathlessness, brain fog, palpitations, POTS. Managed in specialist clinics. May affect ~10% of infections
- MIS-C (Multisystem Inflammatory Syndrome in Children): Post-infectious hyperinflammatory syndrome resembling Kawasaki disease — rare but serious
UKMLA Exam Tips
- 1Dexamethasone 6 mg for up to 10 days in hospitalised patients requiring OXYGEN — the single most important treatment finding from RECOVERY trial
- 2Do NOT give dexamethasone to non-hypoxic COVID patients — no benefit and may impair viral clearance
- 3Lymphopenia (not neutrophilia) is the characteristic blood finding in COVID — unlike typical bacterial infection
- 4COVID increases VTE risk significantly — thromboprophylaxis for all inpatients, low threshold for CTPA
- 5"Silent hypoxia" — patients may have SpO2 <90% without proportionate breathlessness. Always check oximetry
- 6Long COVID defined as symptoms >12 weeks — fatigue and brain fog are the most common persistent symptoms
- 7Anosmia/ageusia: relatively specific symptom for COVID (though now also seen with other respiratory viruses post-pandemic)
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