COVID-19

Overview

COVID-19 is an infectious disease caused by a coronavirus that can affect the nose, throat, lungs, and other parts of the body. It spreads mainly through respiratory droplets and small airborne particles released when an infected person breathes, talks, coughs, or sneezes. COVID-19 can range from a mild illness similar to a cold to a severe infection that requires hospital care.

Many people recover with supportive care, but some may develop complications, especially if they are older, pregnant, immunocompromised, or living with chronic medical conditions. Because the virus can change over time, symptoms, contagiousness, and public health recommendations may vary by region and season.

Vaccination, good hand hygiene, staying home when ill, improving ventilation, and using masks in higher-risk settings can help reduce the spread of COVID-19 and other respiratory infections.

Symptoms

Symptoms of COVID-19 may appear a few days after exposure, although the timing can vary. Some people have no symptoms but can still spread the virus to others.

Common symptoms may include:

• Fever or chills
• Cough
• Sore throat
• Runny or blocked nose
• Fatigue or weakness
• Headache
• Muscle or body aches
• Shortness of breath
• Loss or change of smell or taste
• Nausea, vomiting, or diarrhea

Symptoms can be mild at first and may worsen in some people. Severe illness may involve breathing difficulty, low oxygen levels, pneumonia, or complications affecting the heart, kidneys, nervous system, or blood clotting.

Some people experience ongoing symptoms after the initial infection. This is often referred to as long COVID and may include fatigue, shortness of breath, concentration problems, sleep disturbances, chest discomfort, or persistent cough. The duration and severity vary from person to person.

Causes and Risk Factors

COVID-19 is caused by infection with the virus SARS-CoV-2. The virus spreads most easily in crowded, poorly ventilated indoor spaces and during close contact with an infected person. Transmission can occur before symptoms begin, during symptomatic illness, and sometimes from people who never develop symptoms.

Risk factors for infection include close contact with someone who has COVID-19, being in crowded indoor settings, travel or exposure in areas with high transmission, and inconsistent use of preventive measures when risk is elevated.

Some people have a higher risk of severe illness, including:

• Older adults
• People with chronic lung, heart, kidney, liver, or neurological conditions
• People with diabetes or obesity
• People with weakened immune systems
• Pregnant individuals
• People receiving certain treatments that affect immunity
• Residents of long-term care or communal living settings

Having a risk factor does not mean severe illness will occur, and people without risk factors can also become seriously ill. Individual risk depends on overall health, immune status, vaccination history, and the current circulating variants.

Diagnosis

COVID-19 is diagnosed by considering symptoms, exposure history, physical examination findings, and laboratory testing. Testing may involve a sample taken from the nose or throat. The most appropriate test depends on the timing of symptoms, availability, and clinical situation.

Rapid tests can provide results quickly, while laboratory-based tests may be used when a more detailed assessment is needed. A negative test does not always rule out infection, especially if testing is done very early or if the sample quality is limited. In some cases, repeat testing or additional evaluation may be recommended by a healthcare professional.

If symptoms are more severe, doctors may assess oxygen levels and may request blood tests or imaging studies to evaluate the lungs or possible complications. Diagnosis and decisions about isolation, travel, work, or school attendance should follow local medical and public health guidance.

Treatment Options

Treatment for COVID-19 depends on symptom severity, age, medical history, risk factors, and how long the person has been ill. Many mild cases can be managed with rest, fluids, and monitoring, but medical advice is important for people at higher risk or with worsening symptoms.

Healthcare professionals may recommend supportive care to relieve symptoms and help the body recover. For people at increased risk of severe illness, specific treatments may be considered early in the course of infection. These decisions should be made by a qualified clinician, because suitability depends on the person’s health status, other medications, and timing of symptoms.

People with moderate or severe COVID-19 may need hospital care. Hospital treatment can include oxygen support, monitoring of vital signs, treatment of complications, and other therapies chosen according to the patient’s condition.

Preventive measures remain important. Vaccination can help reduce the risk of severe illness. People should also follow local guidance on staying home when infectious, mask use, ventilation, and protecting vulnerable individuals.

When to See a Doctor

Seek medical advice if you have symptoms of COVID-19 and are older, pregnant, immunocompromised, or have chronic medical conditions. It is also advisable to contact a healthcare provider if symptoms are persistent, worsening, or if you are unsure whether testing or medical evaluation is needed.

Seek urgent medical care if any warning signs occur, such as:

• Difficulty breathing or shortness of breath at rest
• Chest pain or pressure
• Confusion, fainting, or inability to stay awake
• Bluish or gray lips, face, or nails
• Severe weakness or dehydration
• Symptoms that rapidly worsen

COVID-19 can look similar to other respiratory infections, so professional evaluation may be needed to determine the cause and the safest next steps. If visiting a clinic or hospital, inform the facility about possible COVID-19 symptoms before arrival so appropriate precautions can be taken.