COVID-19, caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), is an infectious disease that emerged in late 2019. It primarily spreads through respiratory droplets, aerosols, and contact with contaminated surfaces. The disease can manifest in varying degrees of severity, from asymptomatic to fatal, and has led to a global pandemic, prompting widespread public health responses and vaccination campaigns.

Individuals at higher risk for severe COVID-19 complications include older adults, and those with underlying health conditions such as cardiovascular disease, diabetes, obesity, chronic respiratory conditions, and immunocompromised states. Socioeconomic factors, including access to healthcare and underlying systemic inequalities, can also exacerbate risks. Emerging variants of the virus may influence transmissibility and severity, necessitating ongoing surveillance.

Common symptoms of COVID-19 include fever, cough, fatigue, loss of taste or smell, and difficulty breathing, typically appearing 2-14 days after exposure to the virus. While many individuals experience mild to moderate illness, some may develop severe complications such as pneumonia, acute respiratory distress syndrome (ARDS), or multi-organ failure. Long-term effects, referred to as 'long COVID', can persist for weeks or months following the acute phase of the disease.

COVID-19 is primarily caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which spreads predominantly through respiratory droplets when an infected person coughs, sneezes, talks, or breathes. The virus can also be transmitted by touching surfaces contaminated with the virus and subsequently touching the face, particularly the mouth, nose, or eyes. Close contact with infected individuals, especially in crowded or enclosed spaces, increases the likelihood of transmission, and asymptomatic carriers can unknowingly spread the virus to others.

COVID-19 diagnosis is primarily confirmed through molecular testing (such as RT-PCR) or antigen testing of respiratory samples. Serologic testing can assess for previous infection but is not typically used for acute diagnosis. Clinical assessment, including symptoms and exposure history, along with diagnostic testing, guides the evaluation and management of suspected cases.

While there is no specific antiviral treatment approved for COVID-19, management typically involves supportive care to alleviate symptoms. Mild cases may be treated at home with rest, hydration, and over-the-counter medications to reduce fever and relieve pain. In more severe cases, particularly those requiring hospitalization, treatments may include supplemental oxygen, antivirals such as remdesivir, corticosteroids like dexamethasone, and monoclonal antibodies, depending on the severity of the illness.

Preventive measures for COVID-19 include vaccination, mask-wearing, hand hygiene, and physical distancing. Vaccination is proven to reduce the risk of severe disease and transmission, while masks can help contain respiratory droplets in crowded or indoor settings. Public health guidelines recommend regular handwashing and avoiding close contact with symptomatic individuals to mitigate risk of infection.