Coronavirus disease 2019 (COVID-19) is a contagious disease caused by the virus SARS-CoV-2. The first known case was identified in China, in December 2019. The disease quickly spread worldwide, resulting in the COVID-19 pandemic.
The symptoms of COVID-19 are variable but often include fever, cough fatigue, breathing difficulties, loss of smell, and loss of taste. Symptoms may begin one to fourteen days after exposure to the virus. At least a third of people who are infected do not develop noticeable symptoms. Of those who develop symptoms noticeable enough to be classified as patients, most develop mild to moderate symptoms (up to mild pneumonia), while few develop severe symptoms (dyspnea, hypoxia, or more than 50% lung involvement on imaging), and few develop critical symptoms (respiratory failure, shock, or multiorgan dysfunction). Older people are at a higher risk of developing severe symptoms.
Transmission
COVID-19 transmits when infectious particles are breathed in or come into contact with the eyes, nose, or mouth. The risk is highest when people are in close proximity, but small airborne particles containing the virus can remain suspended in the air and travel over longer distances, particularly indoors. Transmission can also occur when people touch their eyes, nose, or mouth after touching surfaces or objects that have been contaminated by the virus. People remain contagious for up to 20 days and can spread the virus even if they do not develop symptoms.
Testing methods for COVID-19 to detect the virus’s nucleic acid include real-time reverse transcription polymerase chain reaction (RT‑PCR), from a nasopharyngeal swab.
The cornerstone of management of COVID-19 has been supportive care, which includes treatment to relieve symptoms, fluid therapy, oxygen support, and prone positioning as needed, and medications or devices to support other affected vital organs.
Most cases of COVID-19 are mild. In these, supportive care includes medication such as paracetamol or NSAIDs to relieve symptoms (fever, body aches, cough), proper intake of fluids, rest, and nasal breathing. Good personal hygiene and a healthy diet are also recommended. As of April 2020, the U.S. Centers for Disease Control and Prevention (CDC) recommended that those who suspect they are carrying the virus isolate themselves at home and wear a face mask.
As of November 2020, the glucocorticoid dexamethasone had been strongly recommended in those severe cases treated in hospitals with low oxygen levels, to reduce the risk of death. Noninvasive ventilation and admission to an intensive care unit for mechanical ventilation may be required to support breathing. Extracorporeal membrane oxygenation (ECMO) has been used to address respiratory failure, but its benefits are still under consideration. Some of the cases of severe disease course are caused by systemic hyper-inflammation, the so-called cytokine storm.