COVID-19

COVID-19
Caption	Illustration of the SARS-CoV-2 virion
Field	Infectious disease, virology

COVID-19. COVID-19 is an infectious disease caused by the SARS-CoV-2 virus, first identified in Wuhan, Hubei, China in late 2019. The ensuing outbreak was declared a Public Health Emergency of International Concern by the World Health Organization in January 2020 and characterized as a pandemic in March 2020. The disease has had profound global impacts on public health, economies, and societies, leading to unprecedented international responses from entities like the Centers for Disease Control and Prevention and the European Centre for Disease Prevention and Control.

Signs and symptoms

The clinical presentation ranges from asymptomatic infection to severe, life-threatening illness. Common symptoms include fever, cough, fatigue, and loss of taste or smell, known as anosmia. More severe cases can progress to symptoms indicative of pneumonia, acute respiratory distress syndrome (ARDS), and sepsis. Multisystem inflammatory syndromes, such as Multisystem inflammatory syndrome in children (MIS-C) and a similar condition in adults (MIS-A), have been documented as serious complications. Other reported manifestations involve thrombosis, myocarditis, and various neurological symptoms.

Causes

The disease is caused by infection with the SARS-CoV-2 virus, a member of the Coronaviridae family and the Betacoronavirus genus. The virus is closely related to coronaviruses that caused the Severe acute respiratory syndrome (SARS) and Middle East respiratory syndrome (MERS) outbreaks. Its genome is composed of positive-sense single-stranded RNA and it enters human cells primarily by binding the angiotensin-converting enzyme 2 (ACE2) receptor via its spike protein. Research into its origins has been conducted by institutions like the National Institutes of Health and the Chinese Center for Disease Control and Prevention.

Transmission

Primary transmission occurs through respiratory droplets and aerosols expelled by infected individuals during activities like coughing, sneezing, or speaking. Transmission can also occur via fomites (contaminated surfaces), though this is considered less common. The virus is highly transmissible, with significant spread documented in settings such as nursing homes, cruise ships like the Diamond Princess, and large gatherings. Asymptomatic and pre-symptomatic transmission are major drivers of the pandemic, complicating containment efforts by public health authorities worldwide.

Diagnosis

Diagnosis is primarily confirmed through laboratory testing. The standard method is the reverse transcription polymerase chain reaction (RT-PCR) test, which detects viral RNA from samples collected via nasopharyngeal swab. Rapid antigen tests, which detect viral proteins, offer faster results but are generally less sensitive. Serological tests that detect antibodies against the virus, such as ELISA, are used to identify past infections. Imaging techniques like chest radiography and computed tomography (CT) scans can reveal patterns of pneumonia associated with the disease.

Prevention

Preventive measures have been central to public health strategies. These include vaccination with products from Pfizer–BioNTech, Moderna, Johnson & Johnson, and AstraZeneca. Non-pharmaceutical interventions such as face masks, hand washing, social distancing, and improved ventilation are recommended. Many governments implemented lockdowns, travel restrictions, and quarantine protocols. International coordination on prevention has involved the World Health Organization, the Coalition for Epidemic Preparedness Innovations, and national bodies like the Robert Koch Institute.

Treatment

Management depends on disease severity. For mild cases, treatment is supportive, including rest and hydration. For moderate to severe illness, therapeutic options have evolved. Dexamethasone is used for patients requiring oxygen therapy. Antiviral medications like remdesivir, nirmatrelvir/ritonavir (Paxlovid), and molnupiravir are authorized for use. Monoclonal antibody therapies, such as those developed by Regeneron Pharmaceuticals, have been used, though their efficacy varies against emerging variants. Severe cases may require advanced support in an intensive care unit, including mechanical ventilation.

Prognosis and epidemiology

The prognosis varies widely; most infections are mild, but severe disease and death are more likely in older adults and those with underlying conditions like cardiovascular disease, diabetes, or chronic obstructive pulmonary disease. The global case fatality rate has fluctuated over time and by region. As of 2023, there have been hundreds of millions of confirmed cases and millions of deaths reported to the World Health Organization. Major epidemic waves have been associated with variants of concern, including the Alpha variant, Delta variant, and Omicron variant. Surveillance efforts are led by organizations such as the GISAID initiative and the Africa Centres for Disease Control and Prevention.

Category:Infectious diseases Category:Viral diseases Category:Respiratory diseases Category:Pandemics Category:2019 disasters