Covid-19
Symptoms, Causes & Treatment
COVID-19 is an infectious disease caused by SARS-CoV-2. Most people experience mild to moderate illness. Some — particularly older people and those with chronic conditions — develop more severe disease.
What is Covid-19?
COVID-19 ranges in severity from asymptomatic infection to critical illness. With widespread vaccination and antiviral availability, serious outcomes are largely preventable in eligible high-risk individuals. Long COVID affects a proportion of patients with ongoing symptoms lasting beyond 12 weeks.
Symptoms of Covid-19
COVID-19 symptoms range widely from mild cold-like illness to severe pneumonia. Loss of taste or smell remains characteristic of some variants.
Fever · New continuous cough · Loss of taste or smell · Breathlessness · Fatigue and muscle aches · Sore throat · Headache · Runny or blocked nose · Nausea, vomiting, or diarrhoea · Chills and sweating
Severe breathlessness at rest · Confusion or delirium · Persistent chest pain or pressure · Cyanosis (blue lips) · SpO2 below 92% · Unable to wake or stay awake
Severe breathlessness at rest, confusion, SpO2 below 92%, cyanosis, or unable to stay awake — call 999 immediately.
What Causes Covid-19?
COVID-19 is caused by SARS-CoV-2. Understanding the range of severity and risk factors allows appropriate treatment decisions.
SARS-CoV-2 (the virus causing Covid-19) primarily affects the respiratory tract, causing acute COVID-19 illness. It can also cause systemic inflammation, thrombosis, and multi-organ involvement in severe cases. The Omicron variant predominantly causes upper respiratory symptoms.
Long COVID affects up to 10–35% of people after acute infection. Symptoms include fatigue, post-exertional malaise, brain fog, breathlessness, and sleep disturbance. The mechanism is multifactorial and includes persistent inflammation, autonomic dysfunction, and viral persistence.
At-risk individuals (elderly, immunocompromised, pregnant, or with comorbidities) face higher risks of severe COVID-19. Antiviral treatment (nirmatrelvir/ritonavir) and monoclonal antibodies are available for high-risk groups within 5 days of symptom onset.
COPD and asthma exacerbations are commonly precipitated by respiratory infections. Bacteria (H. influenzae, M. catarrhalis) and viruses (rhinovirus) are the main triggers. Treatment involves bronchodilators, antibiotics, and short-course steroids.
Aspiration pneumonia occurs when oropharyngeal secretions or gastric content enter the lungs. It is more common in the elderly, those with dysphagia, reduced consciousness, or significant GORD.
Hospital-acquired pneumonia develops 48+ hours after admission. It is caused by more resistant organisms including MRSA, Pseudomonas, and Gram-negatives. It has a higher mortality than community-acquired pneumonia.
Key Risk Factors
Diagnosing Covid-19
Diagnosis is confirmed by lateral flow or PCR testing. Oxygen saturation assessment guides whether hospital care is needed.
Treatment for Covid-19
Mild COVID is managed with supportive care. High-risk patients may be eligible for antivirals. Hospitalised patients receive oxygen, dexamethasone, and anticoagulation.
Supportive Measures
Rest, hydrate, and take paracetamol for fever. Monitor oxygen saturation. Isolate to prevent spread. Seek urgent care if SpO2 drops below 92% or symptoms significantly worsen.
Long COVID Management
Long COVID (symptoms persisting beyond 12 weeks) requires holistic GP assessment, investigations to exclude other diagnoses, referral to a Long COVID clinic, and graded rehabilitation. Pacing is essential.
When to Seek Help
Severe breathlessness at rest, confusion, SpO2 below 92%, persistent chest pain, cyanosis, or unable to stay awake — call 999 immediately.
If high-risk and testing positive, contact your GP or COVID treatment service within 24 hours to assess eligibility for antiviral treatment.
Preventing Covid-19
COVID-19 is preventable through vaccination, ventilation, and early antiviral treatment for high-risk individuals.
Stay up to date with all COVID-19 booster vaccinations. Updated vaccines against new variants significantly reduce risk of severe illness and hospitalisation, particularly in high-risk individuals.
Good ventilation, avoiding crowded indoor spaces during high prevalence periods, and using masks in high-risk settings (healthcare, immunocompromised contacts) all reduce transmission risk.
Seek early antiviral treatment (Paxlovid) if you are high-risk and develop COVID symptoms. Antivirals must be started within 5 days of symptom onset for maximum benefit.
Use allergen-proof mattress and pillow covers, wash bedding weekly at 60°C, avoid soft furnishings in the bedroom, and consider using a HEPA air purifier to reduce house dust mite exposure.
A healthy diet rich in vitamins C and D, regular exercise, adequate sleep, and avoidance of excess alcohol all support immune function and reduce susceptibility to respiratory infections.
Wash hands frequently with soap and water. Avoid touching the face. Stay away from people with respiratory infections when possible, particularly if elderly or immunocompromised.
Getting Treatment for Covid-19
Most mild COVID-19 can be managed at home. High-risk individuals may be eligible for antiviral treatment through their GP. An online GP consultation can assess eligibility and advise on monitoring.
Expert clinical advice, when you need it.
Covid-19 — Frequently Asked Questions
COVID-19 is caused by SARS-CoV-2 and typically spreads through respiratory droplets when an infected person coughs, sneezes, talks, or breathes. It can also spread through aerosols in poorly ventilated indoor spaces. Good ventilation, vaccination, and prompt isolation when symptomatic reduce transmission.
Most people with COVID-19 recover fully at home with rest, fluids, and paracetamol for fever. Monitor your oxygen saturation with a pulse oximeter if available. Go to A&E if SpO2 falls below 92%, you develop severe breathlessness at rest, confusion, or chest pain that persists.
Long COVID refers to symptoms lasting more than 12 weeks after an acute COVID-19 infection that cannot be explained by another diagnosis. Common symptoms include fatigue, post-exertional malaise, breathlessness, brain fog, and palpitations. Your GP can refer you to a Long COVID service if appropriate.
High-risk individuals include those over 70, the immunocompromised, pregnant women, and those with significant comorbidities. Nirmatrelvir/ritonavir (Paxlovid) must be started within 5 days of symptom onset. Eligibility is assessed by your GP or COVID treatment service.
If you test positive, isolate for at least 5 days from symptom onset or first positive test. Avoid contact with vulnerable people. NHS guidance on isolation periods may vary — check the current guidance on NHS.UK. Inform close contacts so they can monitor for symptoms.
Yes. COVID vaccines remain highly effective at preventing severe illness, hospitalisation, and death, even when they provide less protection against infection with new variants. Updated booster doses against current variants are offered annually to high-risk groups in the UK.
See a GP if you have persistent symptoms beyond 4 weeks after COVID-19, particularly fatigue, breathlessness, chest pain, palpitations, or cognitive difficulties. Persistent symptoms may indicate Long COVID or complications requiring investigation.
Most people with COVID-19 develop a mild to moderate illness and recover fully within 2–4 weeks. The elderly, immunocompromised, and those with comorbidities are at highest risk of severe illness and Long COVID. Vaccination significantly reduces the risk of severe outcomes.