COVID-19 — SARS-CoV-2, Variants, Vaccines, Long COVID & Treatment Guide — Symptoms, Causes & Treatment | MyMedicPlus

COVID-19 (coronavirus disease 2019) is an acute respiratory illness caused by SARS-CoV-2 (Severe Acute Respiratory Syndrome Coronavirus 2), a novel beta-coronavirus first identified in Wuhan, China in December 2019. SARS-CoV-2 spreads primarily via respiratory droplets and aerosols. The virus enters cells through the ACE2 receptor, which is expressed in the lungs, heart, kidneys, gut, and blood vessels, explaining its multi-organ effects. Variants of concern (VOCs) have emerged sequentially: Alpha, Beta, Gamma, Delta (highly virulent), and Omicron (high transmissibility, reduced severity). COVID-19 clinical spectrum ranges from asymptomatic infection (25-40%) to mild respiratory illness, moderate pneumonia, severe hypoxaemic respiratory failure, critical multi-organ failure, and death. As of 2024-2025, SARS-CoV-2 has transitioned to an endemic respiratory pathogen, with periodic surge waves driven by new immune-evading variants; COVID-19 vaccination — particularly updated bivalent and XBB-based formulations — remains the cornerstone of protection against severe disease, hospitalisation, and death across all age groups globally.

SARS-CoV-2 is transmitted through respiratory droplets (greater than 5 micrometres) and aerosols (less than 5 micrometres — dominant in enclosed poorly ventilated spaces); close contact transmission; contact with contaminated surfaces (fomites — less significant route). Risk factors for severe COVID-19: age over 60 (risk doubles with each decade over 40); obesity (BMI over 30); diabetes mellitus; cardiovascular disease; chronic lung disease (COPD, asthma); chronic kidney disease; immunosuppression (chemotherapy, organ transplant, high-dose steroids, HIV with low CD4 count); pregnancy; active smoking; and certain genetic factors (variants in TLR7, IFNAR1). Vaccination status: unvaccinated individuals are at significantly higher risk of severe disease, hospitalisation, and death than vaccinated individuals.

Incubation period: 2-14 days (average 5-7 days). Typical symptoms (Omicron era): sore throat (most common), runny nose, headache, fatigue, muscle aches, dry cough, low-grade fever, and loss of smell and taste (anosmia/ageusia — less common with Omicron than earlier variants). Moderate/severe COVID-19: high fever, persistent cough, shortness of breath (dyspnoea), oxygen saturation below 94% on pulse oximetry. Critical COVID-19: severe respiratory failure requiring mechanical ventilation (ARDS — acute respiratory distress syndrome), septic shock, multi-organ failure, acute kidney injury, and thromboembolism (pulmonary embolism, deep vein thrombosis). Rare complications: MIS-C (multisystem inflammatory syndrome in children), cytokine storm, acute cardiac injury, and COVID-19-associated coagulopathy. Long COVID: symptoms persisting 12 weeks after acute infection — see Complications.

Rapid antigen test (RAT/lateral flow test — LFT): detects SARS-CoV-2 antigen in nasopharyngeal or combined nasal/throat swab; results in 15-30 minutes; sensitivity 70-85% for symptomatic infection (lower for asymptomatic or early infection); specificity very high (99%+). RT-PCR test (reverse transcription polymerase chain reaction): gold standard; detects viral RNA; higher sensitivity than RAT; results in 12-24 hours from accredited laboratory; detects infection earlier and remains positive longer. Chest CT: ground-glass opacities (GGO) in a peripheral, bilateral, lower-lobe predominant distribution — characteristic COVID-19 pneumonia pattern ('crazy paving'); CT severity score guides management. Pulse oximetry: continuous monitoring of SpO2 — 'silent hypoxia' (low SpO2 without breathlessness) is a characteristic feature of COVID-19 pneumonia. Blood tests in severe COVID-19: CRP (elevated), LDH, ferritin, D-dimer (elevated in coagulopathy), IL-6, full blood count (lymphopenia characteristic).

Mild COVID-19 (non-hospitalised, without risk factors): symptomatic treatment — rest, hydration, paracetamol or ibuprofen for fever/pain; self-isolation. Antiviral therapy for high-risk non-hospitalised patients (commenced within 5 days of symptom onset): nirmatrelvir/ritonavir (Paxlovid — oral, protease inhibitor combination) — reduces hospitalisation and death by 89% in unvaccinated high-risk individuals; remdesivir (IV, nucleoside analogue — reduces hospitalisation risk 87%); molnupiravir (oral — reduces hospitalisation by 30%, less effective than Paxlovid). Moderate-severe hospitalised COVID-19: supplemental oxygen (target SpO2 94-96%); dexamethasone 6 mg daily for 10 days (RECOVERY trial — reduces mortality by 25% in patients requiring oxygen); remdesivir (if within 10 days of symptom onset, requiring oxygen but not intubated); baricitinib (JAK inhibitor) or tocilizumab (IL-6 inhibitor) for severe hyperinflammatory disease. Critical COVID-19 (ARDS): prone positioning; protective lung ventilation (low tidal volume 6 mL/kg); ECMO (extracorporeal membrane oxygenation) for refractory hypoxaemia. COVID-19 vaccines: primary prevention of severe disease and death — mRNA vaccines (BNT162b2/Comirnaty, mRNA-1273/Spikevax); adenoviral vector vaccines (AZD1222/Vaxzevria); updated formulations targeting dominant Omicron sub-lineages (XBB.1.5, JN.1, KP.2).

Untreated moderate-to-severe COVID-19 in high-risk individuals can progress to life-threatening ARDS, multi-organ failure, and death. COVID-19-associated coagulopathy causes pulmonary embolism (in 10-20% of critically ill patients), deep vein thrombosis, and stroke. MIS-C (multisystem inflammatory syndrome in children): rare but serious complication weeks after COVID-19 — high fever, rash, abdominal pain, cardiac dysfunction. Long COVID (Post-COVID syndrome): affects an estimated 10-30% of people after COVID-19, including vaccinated individuals — over 65 million people globally. Symptoms persisting 12 weeks: fatigue (most common), cognitive impairment ('brain fog'), exertional dyspnoea, autonomic dysfunction (postural tachycardia syndrome/POTS), depression and anxiety. Long COVID overlaps with ME/CFS — post-exertional malaise (PEM) is a hallmark feature. Risk factors for long COVID: female sex, older age, obesity, unvaccinated status, severe acute illness, pre-existing mental health conditions.

COVID-19 vaccination is the most effective prevention measure — significantly reduces risk of severe disease, hospitalisation, and death in all approved vaccines. Keep vaccinations up to date with annual boosters targeting circulating variants (recommended for over 65s, immunocompromised, pregnant women, and healthcare workers). Non-pharmacological interventions (NPIs): improving indoor ventilation (open windows, CO2 monitors, HEPA air purifiers); wearing an FFP2/N95 respirator in crowded enclosed spaces; hand hygiene; self-isolation when symptomatic; COVID-19 testing before visiting vulnerable individuals. For long COVID management: pacing and activity management to avoid post-exertional malaise (PEM); multidisciplinary long COVID clinic assessment; symptom-specific treatment (ivabradine/beta-blockers for POTS, melatonin for sleep, cognitive rehabilitation for brain fog); avoid deconditioning; seek specialist assessment for treatable causes (e.g., low cortisol, thyroid dysfunction, reactivated EBV).

Call emergency services immediately for: SpO2 below 92% on a pulse oximeter; severe breathlessness at rest unable to complete a sentence; persistent chest pain or tightness; confusion or drowsiness; or inability to stay awake. Monitor SpO2 at home with a pulse oximeter if you are in a high-risk group — 'silent hypoxia' (falling SpO2 without breathlessness) is a recognised COVID-19 pattern. Contact your GP or call the COVID-19 antiviral service within 5 days of symptom onset if you are at high risk (over 70, immunosuppressed, diabetes, CKD, BMI >35) — antivirals (Paxlovid, remdesivir) must be started within 5 days to be effective. Seek review within 2–4 weeks if symptoms of long COVID are persisting (fatigue, brain fog, breathlessness) — a GP can organise baseline tests and refer to a long COVID clinic where available. All household contacts should isolate if positive.