Coronavirus disease 2019 (COVID-19) is a contagious disease caused by SARS-CoV-2 that spread worldwide, resulting in the COVID-19 pandemic. Symptoms include fever, fatigue, cough, breathing difficulties, and loss of smell or taste. About 1/3 of infected people do not develop noticeable symptoms, while most with symptoms have mild to moderate cases (81%), severe cases (14%), and critical cases (5%). Older people are at higher risk of developing severe symptoms.
Transmission and Prevention
The virus spreads through particles inhaled or contact with eyes, nose, or mouth. People can remain contagious for up to 20 days without symptoms. Testing methods include RT-PCR, transcription-mediated amplification, and RT-LAMP from a nasopharyngeal swab.
Several COVID-19 vaccines have been approved and distributed, along with other preventive measures such as distancing, quarantining, ventilation, face masks, hand washing, and isolating patients. The first case was identified in Wuhan, China in December 2019. Scientists believe the virus entered human populations through natural zoonosis, likely due to climate change, ecosystem destruction, and wildlife trade.
Complications and Symptoms
Complications of COVID-19 include pneumonia, ARDS, multi-organ failure, septic shock, and death. Cardiovascular complications may include heart failure, arrhythmias, and thrombosis. Neurologic manifestations can include seizure, stroke, encephalitis, and Guillain-Barré syndrome.
The virus is caused by a strain of coronavirus known as ‘severe acute respiratory syndrome coronavirus 2’ (SARS-CoV-2). It can lead to serious illnesses such as paediatric multisystem inflammatory syndrome and acute encephalopathy in rare cases. Pregnant women are at increased risk of becoming seriously ill from COVID-19, which can cause complications like miscarriage, premature delivery, and intrauterine growth restriction.
Virus Structure and Variants
SARS-CoV-2 is thought to have an animal origin and is closely related to the original SARS-CoV. The virus has a unique genetic makeup with various variants that have emerged throughout 2020, including Alpha, Beta, Delta, Gamma, and others.
The structural proteins of SARS-CoV-2 include membrane glycoprotein (M), envelope protein (E), nucleocapsid protein (N), and the spike protein (S). The virus can be effectively destroyed by household soap, hospital disinfectants, alcohols, heat, povidone-iodine, and ultraviolet-C (UV-C) irradiation.
Pathology and Diagnosis
The SARS-CoV-2 virus infects cells in the upper and lower respiratory tracts and can affect various systems. It primarily affects the lungs due to access through angiotensin-converting enzyme 2 (ACE2) receptors, entering host cells via a special surface glycoprotein called a ‘spike.’
Infection spreads to ciliated epithelium of the nasopharynx and upper airways, causing diffuse alveolar damage and lymphocyte-containing inflammatory infiltrates in the lungs. White patches containing fluid known as ground-glass opacity have been observed in COVID-19 infected lungs.
Loss of smell results from infection of olfactory epithelium support cells. The virus affects both the central and peripheral nervous systems, leading to neurological issues. Virus detection in CNS is rare but has been detected in brains of those who died from COVID-19.
Vaccination and Prevention
The first COVID-19 vaccine was granted regulatory approval on 2 December 2020 by the UK medicines regulator MHRA. Vaccination, staying at home except to get medical care, wearing a face mask in public, avoiding crowded places, keeping distance from others, ventilating indoor spaces, managing potential exposure durations, washing hands often with soap and water, practising good respiratory hygiene, and avoiding touching the eyes, nose, or mouth with unwashed hands are all recommended.
Long-term Effects
About 10-20% of people with COVID-19 will experience symptoms lasting longer than a month. The disease can affect any system in the body, and symptoms often overlap. WHO chief Tedros Adhanom warned that ‘to a significant number of people, the COVID virus poses a range of serious long-term effects.’
The lungs are the most affected organs in COVID-19, and even asymptomatic people may have findings of pulmonary fibrosis or reduced lung function. Cognitive deficit, dementia, psychotic disorders, epilepsy, and seizures persist at an increased level two years after infection.
Mortality and Risk Factors
The severity of COVID-19 varies, with mild cases typically recovering within two weeks and severe or critical diseases taking three to six weeks to recover. Symptoms can be absent in 3-4% of cases or so severe that they cause hospitalization. People transferred to an ICU had a median time of ten days between hospitalization and death.
Abnormal sodium levels and prolonged prothrombin time are associated with poor prognoses. Some people experience symptoms lasting longer than a month, while others report long-term problems such as fatigue and shortness of breath.
Virus Spread and Origin
The virus is thought to be of natural animal origin, likely through spillover infection from wild bats, and possibly spread to humans through live wildlife trade on the Huanan wet market in Wuhan. Investigations into the origin of the pandemic are ongoing.
Conclusion
Understanding the complexities of COVID-19 is crucial for managing its impact on public health. From transmission and prevention methods to long-term effects, every aspect of this disease requires careful attention and research. As we continue to navigate through the challenges posed by SARS-CoV-2, staying informed and adhering to recommended guidelines can help mitigate risks and protect our communities.
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This page is based on the article COVID-19 published in Wikipedia (retrieved on January 3, 2025) and was automatically summarized using artificial intelligence.
