COVID-19
INTRODUCTION
Coronavirus disease 2019 (COVID-19) is a contagious disease caused by the virus SARS-CoV-2.
The first known case was identified in Wuhan, 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,
headache,[8] 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.[12] 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).[13] Older people
are at a higher risk of developing severe symptoms. Some people continue to experience a range of
effects (long COVID) for years after infection, and damage to organs has been observed.[14] Multiyear studies are underway to further investigate the long-term effects of the disease.[15]
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.[16]
Testing methods for COVID-19 to detect the virus's nucleic acid include real-time reverse transcription
polymerase chain reaction (RT-PCR),[17][18] transcription-mediated amplification,[17][18][19] and reverse
transcription loop-mediated isothermal amplification (RT-LAMP)[17][18] from a nasopharyngeal swab.[20]
Several COVID-19 vaccines have been approved and distributed in various countries, 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 work is underway to develop drugs that inhibit the virus, the primary treatment is symptomatic.
Management involves the treatment of symptoms through supportive care, isolation,
and experimental measures.
COVID-19
Nomenclature
Main article: COVID-19 naming
During the initial outbreak in Wuhan, the virus and disease were commonly referred to as
"coronavirus" and "Wuhan coronavirus",[21][22][23] with the disease sometimes called "Wuhan
pneumonia".[24][25] In the past, many diseases have been named after geographical locations, such as
the Spanish flu,[26] Middle East respiratory syndrome, and Zika virus.[27] In January 2020, the World
Health Organization (WHO) recommended 2019-nCoV[28] and 2019-nCoV acute respiratory
disease[29] 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.[30][31][32] 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".[33][34] The
WHO additionally uses "the COVID-19 virus" and "the virus responsible for COVID-19" in public
communications.
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.[36][37] 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,[38] and toes swelling or
turning purple,[39] and in moderate to severe cases, breathing difficulties.[40] People with the COVID19 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.[40] 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.[41][42][43]
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.[44][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.[45][46] These asymptomatic carriers tend not to get tested and can still spread the
disease.[46][47][48][49] Other infected people will develop symptoms later (called "pre-symptomatic") or
have very mild symptoms and can also spread the virus.[49]
As is common with infections, there is a delay 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[50] possibly being infectious on 1-4 of those days.[51] Most symptomatic people experience
symptoms within two to seven days after exposure, and almost all will experience at least one
symptom within 12 days.[50][52]
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.[53] 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.[54] 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.[55]
COVID-19
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.[56]
Complications
Mechanisms of SARS-CoV-2 cytokine storm and complications
Complications may include pneumonia, acute respiratory distress syndrome (ARDS), multi-organ
failure, septic shock, and death.[57][58][59][60] Cardiovascular complications may include heart
failure, arrhythmias (including atrial fibrillation), heart inflammation, and thrombosis,
particularly venous thromboembolism.[61][62][63][64][65][66] Approximately 20–30% of people who present
with COVID-19 have elevated liver enzymes, reflecting liver injury.[67][68]
Neurologic manifestations include seizure, stroke, encephalitis, and Guillain–Barré syndrome (which
includes loss of motor functions).[69][70] Following the infection, children may develop paediatric
multisystem inflammatory syndrome, which has symptoms similar to Kawasaki disease, which can
be fatal.[71][72] 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.[73]
According to the US Centers for Disease Control and Prevention, pregnant women are at increased
risk of becoming seriously ill from COVID-19.[74] 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.[74]
Fungal infections such as aspergillosis, candidiasis, cryptococcosis and mucormycosis have been
recorded in patients recovering from COVID-19.[75][76]
COVID-19