The COVID-19 pandemic, also known as the coronavirus pandemic, is a global pandemic of coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The novel virus was first identified in an outbreak in the Chinese city of Wuhan in December 2019, and spread to other areas of Asia and then worldwide in early 2020. The World Health Organization (WHO) declared the outbreak a public health emergency of international concern (PHEIC) on 30 January 2020, and assessed the outbreak had become a pandemic on 11 March 2020.[3] The WHO ended the PHEIC on 5 May 2023.[4] As of 11 March 2024, the pandemic has caused 7,033,430[5] confirmed deaths, ranking it fifth in the list of the deadliest epidemics and pandemics in history.
COVID-19 symptoms range from asymptomatic to deadly, but most commonly include fever, sore throat, nocturnal cough, and fatigue. Transmission of the virus is often through airborne particles. Mutations have produced many strains (variants) with varying degrees of infectivity and virulence.[9]
COVID-19 vaccines were widely deployed in various countries beginning in December 2020. Treatments include novel antiviral drugs and symptom control. Common mitigation measures during the public health emergency included travel restrictions, lockdowns, business restrictions and closures, workplace hazard controls, mask mandates, quarantines, testing systems, and contact tracing of the infected.
The pandemic caused severe social and economic disruption around the world, including the largest global recession since the Great Depression.[10] Widespread supply shortages, including food shortages, were caused by supply chain disruptions and panic buying. Reduced human activity led to an unprecedented temporary decrease in pollution. Educational institutions and public areas were partially or fully closed in many jurisdictions, and many events were cancelled or postponed during 2020 and 2021. Telework became much more common for white-collar workers as the pandemic evolved. Misinformation circulated through social media and mass media, and political tensions intensified. The pandemic raised issues of racial and geographic discrimination, health equity, and the balance between public health imperatives and individual rights.
Terminology
Further information: COVID-19 naming
Chinese medics in Huanggang, Hubei, in 2020
In epidemiology, a pandemic is defined as "an epidemic occurring over a very wide area, crossing international boundaries, and usually affecting a large number of people". During the COVID-19 pandemic, as with other pandemics, the meaning of this term has been challenged.[11]
During the initial outbreak in Wuhan, the virus and disease were commonly referred to as "coronavirus", "Wuhan coronavirus",[12] "the coronavirus outbreak" and the "Wuhan coronavirus outbreak",[13] with the disease sometimes called "Wuhan pneumonia".[14][15] In January 2020, the WHO recommended 2019-nCoV[16] and 2019-nCoV acute respiratory disease[17] as interim names for the virus and disease per 2015 international guidelines against using geographical locations (e.g. Wuhan, China), animal species, or groups of people in disease and virus names in part to prevent social stigma.[18] WHO finalized the official names COVID-19 and SARS-CoV-2 on 11 February 2020.[19] Tedros Adhanom Ghebreyesus explained: CO for corona, VI for virus, D for disease and 19 for when the outbreak was first identified (31 December 2019).[20] WHO additionally uses "the COVID-19 virus" and "the virus responsible for COVID-19" in public communications.[19]
WHO named variants of concern and variants of interest using Greek letters. The initial practice of naming them according to where the variants were identified (e.g. Delta began as the "Indian variant") is no longer common.[21] A more systematic naming scheme reflects the variant's PANGO lineage (e.g., Omicron's lineage is B.1.1.529) and is used for other variants.[22][23][24]
Epidemiology
Background
Main articles: Origin of COVID-19 and COVID-19 pandemic in Hubei
SARS-CoV-2 is a virus closely related to bat coronaviruses,[25] pangolin coronaviruses,[26][27] and SARS-CoV.[28] The first known outbreak (the 2019–2020 COVID-19 outbreak in mainland China) started in Wuhan, Hubei, China, in December 2019.[29] Many early cases were linked to people who had visited the Huanan Seafood Wholesale Market there,[30][31][32] but it is possible that human-to-human transmission began earlier.[33][34] Molecular clock analysis suggests that the first cases were likely to have been between October and November 2019.[35]
The scientific consensus is that the virus is most likely of a zoonotic origin, from bats or another closely related mammal.[33][36][37] While other explanations such as speculations that SARS-CoV-2 was accidentally released from a laboratory have been proposed,[38][39][40] such explanations are not supported by evidence.[41]
Cases
Main articles: COVID-19 pandemic by country and territory and COVID-19 pandemic cases
Official "case" counts refer to the number of people who have been tested for COVID-19 and whose test has been confirmed positive according to official protocols whether or not they experienced symptomatic disease.[42][43] Due to the effect of sampling bias, studies which obtain a more accurate number by extrapolating from a random sample have consistently found that total infections considerably exceed the reported case counts.[44][45] Many countries, early on, had official policies to not test those with only mild symptoms.[46][47] The strongest risk factors for severe illness are obesity, complications of diabetes, anxiety disorders, and the total number of conditions.[48]
During the start of the COVID-19 pandemic it was not clear whether young people were less likely to be infected, or less likely to develop symptoms and be tested.[49] A retrospective cohort study in China found that children and adults were just as likely to be infected.[50]
Among more thorough studies, preliminary results from 9 April 2020, found that in Gangelt, the centre of a major infection cluster in Germany, 15 percent of a population sample tested positive for antibodies.[51] Screening for COVID-19 in pregnant women in New York City, and blood donors in the Netherlands, found rates of positive antibody tests that indicated more infections than reported.[52][53] Seroprevalence-based estimates are conservative as some studies show that persons with mild symptoms do not have detectable antibodies.[54]
Initial estimates of the basic reproduction number (R0) for COVID-19 in January 2020 were between 1.4 and 2.5,[55] but a subsequent analysis claimed that it may be about 5.7 (with a 95 percent confidence interval of 3.8 to 8.9).[56]
In December 2021, the number of cases continued to climb due to several factors, including new COVID-19 variants. As of that 28 December, 282,790,822 individuals worldwide had been confirmed as infected.[57] As of 14 April 2022, over 500 million cases were confirmed globally.[58] Most cases are unconfirmed, with the Institute for Health Metrics and Evaluation estimating the true number of cases as of early 2022 to be in the billions.[59][60]