Coronavirus disease 2019 (COVID-19)
Other names	COVID, (the) coronavirus
Transmission and life-cycle of SARS-CoV-2, which causes COVID-19
Pronunciation	/kəˈroʊnəvaɪrəs/ /ˌkoʊvɪdnaɪnˈtiːn, ˌkɒvɪd-/[1]
Specialty	Infectious disease
Symptoms	Fever, cough, fatigue, shortness of breath, vomiting, loss of taste or smell; some cases asymptomatic[2][3]
Complications	Pneumonia, sepsis, ARDS, kidney failure, respiratory failure, pulmonary fibrosis, CKS, MIS-C, long COVID
Usual onset	2–14 days (typically 5) after infection
Duration	5 days to chronic
Causes	SARS-CoV-2
Diagnostic method	RT‑PCR testing, CT scan, rapid antigen test
Prevention	Vaccination, face coverings, quarantine, social distancing, ventilation, hand washing
Treatment	Symptomatic and supportive
Frequency	775,615,722[4] confirmed cases (true case count is expected to be much higher[5])
Deaths	7,051,323[4] (reported) 18.2–33.5 million[6] (estimated)

Coronavirus disease 2019 (COVID-19) is a contagious disease caused by the coronavirus SARS-CoV-2. The first known case was identified in Wuhan, China, in December 2019.^[7] Most scientists believe the SARS-CoV-2 virus entered into human populations through natural zoonosis, similar to the SARS-CoV-1 and MERS-CoV outbreaks, and consistent with other pandemics in human history.^[8][9] Social and environmental factors including climate change, natural ecosystem destruction and wildlife trade increased the likelihood of such zoonotic spillover.^{[10][11] [12][13]} The disease quickly spread worldwide, resulting in the COVID-19 pandemic.

The symptoms of COVID‑19 are variable but often include fever,^[14] fatigue, cough, breathing difficulties, loss of smell, and loss of taste.^[15][16][17] 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.^[18][19] Of those who develop symptoms noticeable enough to be classified as patients, most (81%) develop mild to moderate symptoms (up to mild pneumonia), while 14% develop severe symptoms (dyspnea, hypoxia, or more than 50% lung involvement on imaging), and 5% develop critical symptoms (respiratory failure, shock, or multiorgan dysfunction).^[20] Older people are at a higher risk of developing severe symptoms. Some complications result in death. Some people continue to experience a range of effects (long COVID) for months or years after infection, and damage to organs has been observed.^[21] Multi-year studies are underway to further investigate the long-term effects of the disease.^[22]

COVID‑19 transmission occurs 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.^[23]

Testing methods for COVID-19 to detect the virus's nucleic acid include real-time reverse transcription polymerase chain reaction (RT‑PCR),^[24][25] transcription-mediated amplification,^[24][25][26] and reverse transcription loop-mediated isothermal amplification (RT‑LAMP)^[24][25] from a nasopharyngeal swab.^[27]

Several COVID-19 vaccines have been approved and distributed in various countries, many of which have initiated mass vaccination campaigns. Other preventive measures include physical or social distancing, quarantining, ventilation of indoor spaces, use of face masks or coverings in public, covering coughs and sneezes, hand washing, and keeping unwashed hands away from the face. While drugs have been developed to inhibit the virus, the primary treatment is still symptomatic, managing the disease through supportive care, isolation, and experimental measures.

Nomenclature

During the initial outbreak in Wuhan, the virus and disease were commonly referred to as "coronavirus" and "Wuhan coronavirus",^[28][29][30] with the disease sometimes called "Wuhan pneumonia".^[31][32] In the past, many diseases have been named after geographical locations, such as the Spanish flu,^[33] Middle East respiratory syndrome, and Zika virus.^[34] In January 2020, the World Health Organization (WHO) recommended 2019-nCoV^[35] and 2019-nCoV acute respiratory disease^[36] as interim names for the virus and disease per 2015 guidance and international guidelines against using geographical locations or groups of people in disease and virus names to prevent social stigma.^[37][38][39] The official names COVID‑19 and SARS-CoV-2 were issued by the WHO on 11 February 2020 with COVID-19 being shorthand for "coronavirus disease 2019".^[40][41] The WHO additionally uses "the COVID‑19 virus" and "the virus responsible for COVID‑19" in public communications.^[40][42]

Symptoms and signs

The symptoms of COVID-19 are variable depending on the type of variant contracted, ranging from mild symptoms to a potentially fatal illness.^[43][44] Common symptoms include coughing, fever, loss of smell (anosmia) and taste (ageusia), with less common ones including headaches, nasal congestion and runny nose, muscle pain, sore throat, diarrhea, eye irritation,^[45] and toes swelling or turning purple,^[46] and in moderate to severe cases, breathing difficulties.^[47] People with the COVID-19 infection may have different symptoms, and their symptoms may change over time. Three common clusters of symptoms have been identified: one respiratory symptom cluster with cough, sputum, shortness of breath, and fever; a musculoskeletal symptom cluster with muscle and joint pain, headache, and fatigue; and a cluster of digestive symptoms with abdominal pain, vomiting, and diarrhea.^[47] In people without prior ear, nose, or throat disorders, loss of taste combined with loss of smell is associated with COVID-19 and is reported in as many as 88% of symptomatic cases.^[48][49][50]

Published data on the neuropathological changes related with COVID-19 have been limited and contentious, with neuropathological descriptions ranging from moderate to severe hemorrhagic and hypoxia phenotypes, thrombotic consequences, changes in acute disseminated encephalomyelitis (ADEM-type), encephalitis and meningitis. Many COVID-19 patients with co-morbidities have hypoxia and have been in intensive care for varying lengths of time, confounding interpretation of the data.^[51]

Of people who show symptoms, 81% develop only mild to moderate symptoms (up to mild pneumonia), while 14% develop severe symptoms (dyspnea, hypoxia, or more than 50% lung involvement on imaging) that require hospitalization, and 5% of patients develop critical symptoms (respiratory failure, septic shock, or multiorgan dysfunction) requiring ICU admission.^{[52][needs update]}

At least a third of the people who are infected with the virus do not develop noticeable symptoms at any point in time.^[53][54][55] These asymptomatic carriers tend not to get tested and can still spread the disease.^{[55][56][57][58]} Other infected people will develop symptoms later (called "pre-symptomatic") or have very mild symptoms and can also spread the virus.^[58]

As is common with infections, there is a delay, or incubation period, between the moment a person first becomes infected and the appearance of the first symptoms. The median delay for COVID-19 is four to five days^[59] possibly being infectious on 1-4 of those days.^[60] Most symptomatic people experience symptoms within two to seven days after exposure, and almost all will experience at least one symptom within 12 days.^[59][61]

Most people recover from the acute phase of the disease. However, some people continue to experience a range of effects, such as fatigue, for months, even after recovery.^[62] This is the result of a condition called long COVID, which can be described as a range of persistent symptoms that continue for weeks or months at a time.^[63] Long-term damage to organs has also been observed after the onset of COVID-19. Multi-year studies are underway to further investigate the potential long-term effects of the disease.^[64]

The Omicron variant became dominant in the U.S. in December 2021. Symptoms with the Omicron variant are less severe than they are with other variants.^[65]

Complications

Complications may include pneumonia, acute respiratory distress syndrome (ARDS), multi-organ failure, septic shock, and death.^{[66][67][68][69]} Cardiovascular complications may include heart failure, arrhythmias (including atrial fibrillation), heart inflammation, and thrombosis, particularly venous thromboembolism.^{[70][71][72][73][74][75]} Approximately 20–30% of people who present with COVID‑19 have elevated liver enzymes, reflecting liver injury.^[76][77]

Neurologic manifestations include seizure, stroke, encephalitis, and Guillain–Barré syndrome (which includes loss of motor functions).^[78][79] Following the infection, children may develop paediatric multisystem inflammatory syndrome, which has symptoms similar to Kawasaki disease, which can be fatal.^[80][81] In very rare cases, acute encephalopathy can occur, and it can be considered in those who have been diagnosed with COVID‑19 and have an altered mental status.^[82]

According to the US Centers for Disease Control and Prevention, pregnant women are at increased risk of becoming seriously ill from COVID‑19.^[83] This is because pregnant women with COVID‑19 appear to be more likely to develop respiratory and obstetric complications that can lead to miscarriage, premature delivery and intrauterine growth restriction.^[83] Zdroj:https://en.wikipedia.org?pojem=COVID-19_safety_measures
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