Coronavirus
Overview
Coronavirus is the collective term for positive-sense single-stranded RNA viruses belonging to the family Coronaviridae. The name was coined in the 1960s because the spike proteins on the viral surface resemble the Sun's corona. In humans, coronaviruses cause illnesses ranging from mild respiratory infections such as the common cold to severe respiratory syndromes (SARS, MERS), and the novel coronavirus disease of 2019 (COVID-19). They are regarded as the group of pathogens that has had the greatest impact on human health in the 21st century.
Main Content
Classification and Structure
The family Coronaviridae is divided into four genera: alpha, beta, gamma, and delta. Those that infect humans are mainly alphacoronaviruses (HCoV-229E, NL63) and betacoronaviruses (HCoV-OC43, HKU1, SARS-CoV, MERS-CoV, SARS-CoV-2). Virus particles have an envelope about 80–120 nm in size; embedded in the envelope are the spike (S) protein, membrane (M) protein, and envelope (E) protein, while inside, the nucleocapsid (N) protein wraps the RNA genome. The genome is about 30,000 base pairs, the largest among RNA viruses, and because the replication process includes an exonuclease proofreading function, its mutation rate is relatively lower than that of other RNA viruses, though the emergence of variants is still active.
Transmission Routes and Symptoms
The main routes of transmission are inhalation of droplets and aerosols from infected individuals, and contact with contaminated surfaces followed by touching of mucous membranes. The spike protein binds to the ACE2 receptor on host cells and then enters the cell with the help of proteases such as TMPRSS2. The incubation period is 2–14 days (mostly around 5 days), and typical symptoms include fever, dry cough, sore throat, fatigue, muscle pain, and loss of smell and taste. In severe progression, pneumonia, acute respiratory distress syndrome (ARDS), cytokine storm, and thrombosis appear. The risk is higher for the elderly and those with underlying medical conditions.
The COVID-19 Pandemic
After a cluster of pneumonia of unknown cause occurred in Wuhan, China, in December 2019, the causative pathogen was identified in January 2020 as a novel coronavirus (SARS-CoV-2). The WHO declared a pandemic on March 11, 2020, and lifted the Public Health Emergency of International Concern (PHEIC) in May 2023. Cumulative confirmed cases exceeded 700 million, and deaths were counted at more than 7 million (by excess mortality estimates, the true figure is presumed to be far higher).
Diagnosis and Treatment
RT-PCR testing is the standard for diagnosis, while rapid antigen tests (RAT) are convenient but less sensitive. Antibody tests are used to confirm past infection. For treatment, symptomatic therapy is central in mild cases, and antiviral agents (nirmatrelvir/ritonavir, remdesivir) and monoclonal antibodies are used in high-risk groups. For severe patients, steroids such as dexamethasone, oxygen therapy, and ECMO are applied.
Vaccines and Prevention
mRNA vaccines (Pfizer-BioNTech, Moderna), viral vector vaccines (AstraZeneca, Janssen), inactivated vaccines (Sinovac, Sinopharm), and recombinant protein vaccines (Novavax) were developed. Vaccines are highly effective at preventing severe disease and death, but immunity wanes over time, requiring booster doses. Prevention basically consists of wearing masks, hand hygiene, ventilation, social distancing, and isolation upon confirmation of infection.
Latest Trends
As of 2024–2025, COVID-19 has become established as one of the seasonal respiratory infectious diseases. Descendant variants of the Omicron lineage (JN.1, KP.3, XEC, and the FLiRT and BA.2.86 lineages that spread from late 2024 onward) predominate, and while immune evasion has increased, pathogenicity has remained relatively stable. Countries have shifted to a system of "simultaneous respiratory vaccine administration," giving COVID-19 vaccines together with influenza vaccines once a year, and post-XBB generation vaccines based on JN.1 and KP.2 are in use. The WHO continues to recommend sharing genomic sequences for variant surveillance. Meanwhile, the pandemic experience has left long-term impacts on mRNA platform technology, telemedicine, and infectious disease response governance, and the causes and treatments of Long COVID remain an active research topic. Debates over the virus's origins and research on the relationship between vaccination and post-infection sequelae also continue.
Related Topics
- [[COVID-19]]
- [[SARS-CoV-2]]
- [[Vaccine]]
- [[mRNA Vaccine]]
- [[Pandemic]]
- [[Omicron Variant]]
- [[Long COVID]]
- [[Respiratory Infectious Diseases]]