COVID-19
Also known as: SARS-CoV-2, Coronavirus
COVID 19 is the disease caused by infection with SARS-CoV-2, a coronavirus first identified in late 2019, transmitted predominantly via respiratory droplets and aerosols.
Clinical severity ranges widely, from asymptomatic infection through to critical illness with respiratory failure, and has been shaped considerably over time by viral variant, vaccination status, and prior infection derived immunity within the population.
Common symptoms include fever, cough, fatigue, myalgia, sore throat, and headache.
Loss of smell or taste (anosmia or ageusia), while less prominent with more recent variants than with earlier strains of the virus, remains a recognized and relatively specific symptom when present.
Gastrointestinal symptoms, including diarrhea and nausea, occur in a subset of patients.
Most infections are mild and self limiting.
A minority progress to more significant respiratory involvement, typically in the second week of illness, with progressive dyspnea, hypoxia, and, in severe cases, acute respiratory distress syndrome.
Risk factors for severe disease include older age, obesity, diabetes, cardiovascular disease, chronic respiratory disease, chronic kidney disease, immunosuppression, and pregnancy.
Vaccination substantially reduces the risk of severe disease, hospitalization, and death, though it does not eliminate the risk of infection or mild illness entirely.
Recognized complications include pneumonia, acute respiratory distress syndrome, venous thromboembolism (COVID 19 is associated with a notably increased thrombotic risk), myocarditis, and, in a subset of patients, persistent symptoms extending beyond the acute illness, commonly referred to as long COVID or post COVID condition, which can include persistent fatigue, dyspnea, cognitive difficulty, and other multisystem symptoms lasting weeks to months.
RT-PCR testing of a nasopharyngeal or combined nasal and throat swab remains the gold standard diagnostic test, offering high sensitivity and specificity.
Rapid antigen tests are faster and more accessible, with good specificity but lower sensitivity, particularly early in infection or with lower viral loads, meaning a negative antigen test does not fully exclude infection in a patient with a compatible clinical picture and significant exposure risk.
Further investigation is reserved for patients with more significant illness.
Pulse oximetry is essential in any patient with respiratory symptoms, since hypoxia can be present without proportionate breathlessness in some patients, a phenomenon sometimes termed silent or happy hypoxia.
Chest imaging, either CXR or CT depending on severity and availability, may show bilateral ground glass opacities or consolidation in more significant pulmonary involvement.
Bloods in hospitalized patients typically include FBC, inflammatory markers (CRP, ferritin), D-dimer (though this should be interpreted cautiously given its frequent elevation in COVID 19 without necessarily indicating thromboembolism), and renal and liver function.
Differentials include influenza and other respiratory viral infections, bacterial pneumonia, and, particularly during overlapping seasons, distinguishing between these requires specific testing since clinical features alone are often insufficiently discriminating.
Mild disease in a low risk patient is managed with supportive care alone: rest, hydration, and antipyretics or simple analgesics as needed, with self isolation per current local public health guidance to reduce onward transmission.
Patients at higher risk of progression to severe disease may be eligible for early antiviral or antibody based treatment, guided by local protocols and current drug availability, which have evolved considerably as the virus and available therapeutics have changed over time.
Where available and indicated, options have included oral antivirals such as nirmatrelvir with ritonavir, and, in specific settings, remdesivir, generally most effective when started early in the illness course in patients at genuine risk of progression, rather than used routinely in low risk, mild disease.
Hospitalized patients with hypoxia require supplemental oxygen, titrated to target saturation, with escalation to high flow oxygen, non-invasive ventilation, or invasive mechanical ventilation as required by severity and trajectory, following standard respiratory failure management principles.
Dexamethasone (typically 6 mg once daily for up to ten days) has been shown to reduce mortality in patients requiring supplemental oxygen or ventilatory support, and should be given in this group, but is not indicated and may be harmful in patients with mild disease not requiring oxygen.
Additional immunomodulatory therapy, such as tocilizumab or baricitinib, is used in selected patients with rapidly progressive, severe disease, generally alongside dexamethasone and under specialist guidance.
Venous thromboembolism prophylaxis should be given to all hospitalized patients in the absence of a contraindication, given the recognized elevated thrombotic risk associated with the disease, with treatment dose anticoagulation considered in specific higher risk scenarios per evolving evidence and local protocol.
Persistent post COVID symptoms are managed supportively and symptomatically, with a graded return to activity, since premature intensive exertion has been associated with symptom relapse in some patients, alongside targeted management of specific dominant symptoms such as breathlessness or cognitive difficulty, and referral to a dedicated post COVID service where available.
Referral: hospital admission for hypoxia, significant respiratory distress, or clinical deterioration; respiratory or infectious disease input for complex or prolonged cases; dedicated post COVID services for persistent, functionally limiting symptoms.
