COVID-19, contagious viral disease caused by severe acute respiratory syndrome coronavirus 2, or SARS-CoV-2, a coronavirus that is genetically related to SARS-CoV, which causes SARS. Symptoms generally develop between 2 and 14 days after exposure, with many persons showing symptoms after 5 days. Although some infected individuals may experience no or very mild symptoms, patients typically may have a fever, dry cough, and shortness of breath or difficulty breathing. Some patients experience chills (in some cases with shaking), body aches, headache, fatigue, a sore throat, a sudden loss of smell or taste, and nausea, vomiting, or diarrhea. More serious illness may progress to pneumonia, unusual blood thickening and clotting, heart failure and arrhythmia, and acute respiratory distress syndrome. Persons who are 60 or older or who have such underlying medical conditions as heart or lung disease, diabetes, or certain cancers, appear to be at higher risk for developing more serious complications and dying from the disease. Although children generally have a less severe response to the infection, in rare cases children who have been infected or been around infected persons have developed pediatric multisystem inflammatory syndrome, which is marked by fever, abdominal pain, vomiting, diarrhea, fatigue, rash, bloodshot, or other symptoms and may involve the heart, lungs, kidneys, brain, skin, eyes, or gastrointestinal organs.

Treatment consists of medication that can alleviate the symptoms and other supportive care; the antiviral remdesivir may shorten recovery time by several days, and the steroid dexamethasone may improve survival for patients on a ventilator. There has been significant and rapid research into a potential cure or vaccine, but in their absence, measures such as wearing masks, physical distancing, cleaning hands and surfaces, and quarantine are relied on to control transmission because the virus is spread by droplets produced by coughing or sneezing or through contact with contaminated surfaces. COVID-19 is generally less severe and less deadly than SARS and MERS, with many studies estimating that the actual fatality rate (as opposed to that based on reported cases) is between .5% to 1%, but the virus has proven especially deadly in nursing home settings, and rapid increases in the number of serious cases in some regions have overwhelmed hospitals at times.

As with SARS and MERS, COVID-19 is believed to be caused by a bat coronavirus that spread to humans, but it is unclear how SARS-CoV-2 was transferred. First identified in Wuhan, China, in Dec., 2019, COVID-19 was initially downplayed by local officials and soon became epidemic in China, greatly surpassing the number of cases that occurred in the SARS outbreak (2002–3). The Chinese government publicly acknowledged the seriousness of the epidemic in late Jan., 2020, after the disease was identified in a traveler to Thailand, and the rapid spread of virus led the World Health Organization to declare a global public health emergency at the end of the month. China quarantined Hubei, province where Wuhan is located, as well as a number of other locations, with significant economic impacts.

Despite travel restrictions and spot quarantine efforts by other countries, COVID-19 gradually spread worldwide. Many nations also were initially slow to respond, but most ultimately instituted a range of restrictive public health measures in an attempt to constrain the disease's further spread. Studies have suggested that the disease in fact spread earlier and unnoticed before travel restrictions were in place. By April the disease had had significant health and economic impacts worldwide, especially in Western Europe, Iran, and the United States. The last had the highest number of reported cases and deaths, with the greater New York City area the site of the worst outbreak. By midyear, the worst hit nations were the United States, Brazil, and India, all of which generally instituted less restrictive control measures for shorter periods of time.

The economic effects of COVID-19, due to the measures used to control its spread and to the efforts taken by the people to avoid becoming infected, led to the world's worst economic crisis since the Great Depression. Tens of millions lost their jobs, some only temporarily but others permanently. Increased government spending on unemployment benefits and on aid to businesses helped mitigate some of the economic effects in varying degrees internationally, but also increased government deficits and debt.

The Columbia Electronic Encyclopedia, 6th ed. Copyright © 2023, Columbia University Press. All rights reserved.

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