COVID-19 pandemic
The global COVID-19 pandemic, caused by severe acute respiratory syndrome coronavirus 2, began with an outbreak in Wuhan, China, in December 2019. Soon afterward, it spread to other parts of Asia and then worldwide in early 2020. The World Health Organization declared the outbreak a public health emergency of international concern on 30 January 2020, and assessed it as having become a pandemic on 11 March. The WHO declared the public health emergency caused by COVID-19 had ended in May 2023.
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 with varying degrees of infectivity and virulence. COVID-19 vaccines were developed rapidly and deployed to the general public beginning in December 2020, made available through government and international programmes such as COVAX, aiming to provide vaccine equity. 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. 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 occasionally through 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.
The disease has continued to circulate since 2023. As of 2024, experts were uncertain as to whether it still qualified as a pandemic. Different definitions of pandemics lead to different determinations of when they end. As of, COVID-19 has caused confirmed deaths, and 18.2 to 33.5million estimated deaths. The pandemic ranks as the fifth-deadliest pandemic or epidemic in history.
Terminology
Pandemic
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.The end of a pandemic or other epidemic only rarely involves the total disappearance of a disease, and historically, much less attention has been given to defining the ends of epidemics than their beginnings. The ends of particular epidemics have been defined in a variety of ways, differing according to academic field, and differently based on location and social group. An epidemic's end can be considered a social phenomenon, not just a biological one.
Time reported in March 2024 that expert opinions differ on whether or not COVID-19 is currently considered endemic or pandemic, and that the WHO continued to call the disease a pandemic on its website.
Virus names
During the initial outbreak in Wuhan, the virus and disease were commonly referred to as "coronavirus", "Wuhan coronavirus", "the coronavirus outbreak" and the "Wuhan coronavirus outbreak", with the disease sometimes called "Wuhan pneumonia". In January 2020, the WHO recommended 2019-nCoV and 2019-nCoV acute respiratory disease as interim names for the virus and disease per 2015 international guidelines against using geographical locations, animal species, or groups of people in disease and virus names in part to prevent social stigma. WHO finalised the official names COVID-19 and SARS-CoV-2 on 11 February 2020. WHO Director-General Tedros Ghebreyesus explained: COfor corona, VIfor virus, Dfor disease and 19 for when the outbreak was first identified. WHO additionally uses "the COVID-19 virus" and "the virus responsible for COVID-19" in public communications.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 is no longer common. A more systematic naming scheme reflects the variant's PANGO lineage and is used for other variants.
Epidemiology
Background
SARS-CoV-2 is a virus closely related to bat coronaviruses, pangolin coronaviruses, and SARS-CoV. The first known outbreak started in Wuhan, Hubei, China, in December 2019. Many early cases were linked to people who had visited the Huanan Seafood Wholesale Market there, but it is possible that human-to-human transmission began earlier. Molecular clock analysis suggests that the first cases were likely to have been between October and November 2019.The scientific consensus is that the virus is most likely of a zoonotic origin, from bats or another closely related mammal. While other explanations such as speculations that SARS-CoV-2 was accidentally released from a laboratory have been proposed, as of 2021 these were not sufficiently supported by evidence.
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. 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. Many countries, early on, had official policies to not test those with only mild symptoms. The strongest risk factors for severe illness are obesity, complications of diabetes, anxiety disorders, and the total number of conditions.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. A retrospective cohort study in China found that children and adults were just as likely to be infected.
Among more thorough studies, preliminary results from 9 April 2020 found that in Gangelt, the centre of a major infection cluster in Germany, 15 per cent of a population sample tested positive for antibodies. 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. Seroprevalence-based estimates are conservative as some studies show that persons with mild symptoms do not have detectable antibodies.
Initial estimates of the basic reproduction number for COVID-19 in January 2020 were between 1.4 and 2.5, but a subsequent analysis claimed that it may be about 5.7.
In December 2021, the number of cases continued to climb due to several factors, including new COVID-19 variants. As of that 28December, 282,790,822 individuals worldwide had been confirmed as infected., over 500 million cases were confirmed globally. 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.
Test positivity rate
One measure that public health officials and policymakers have used to monitor the pandemic and guide decision-making is the test positivity rate. According to Johns Hopkins in 2020, one benchmark for a "too high" per cent positive is 5%, which was used by the WHO in the past.Deaths
As of, more than deaths had been attributed to COVID-19. The first confirmed death was in Wuhan on 9 January 2020. These numbers vary by region and over time, influenced by testing volume, healthcare system quality, treatment options, government response, time since the initial outbreak, and population characteristics, such as age, sex, and overall health.Multiple measures are used to quantify mortality. Official death counts typically include people who died after testing positive. Such counts exclude deaths without a test. Conversely, deaths of people who died from underlying conditions following a positive test may be included. Countries such as Belgium include deaths from suspected cases, including those without a test, thereby increasing counts.
Official death counts have been claimed to underreport the actual death toll, because excess mortality data show an increase in deaths that is not explained by COVID-19 deaths alone. Using such data, estimates of the true number of deaths from COVID-19 worldwide have included a range from 18.2 to 33.5 million by 18 November 2023 by The Economist, as well as over 18.5 million by 1 April 2023 by the Institute for Health Metrics and Evaluation and ≈18.2 million deaths between 1 January 2020, and 31 December 2021, by a comprehensive international study.
News article about the study: Such deaths include deaths due to healthcare capacity constraints and priorities, as well as reluctance to seek care. Further research may help distinguish the proportions directly caused by COVID-19 from those caused by indirect consequences of the pandemic.
In May 2022, the WHO estimated the number of excess deaths by the end of 2021 to be 14.9 million compared to 5.4 million reported COVID-19 deaths, with the majority of the unreported 9.5 million deaths believed to be direct deaths due the virus, rather than indirect deaths. Some deaths were because people with other conditions could not access medical services.
A December 2022 WHO study estimated excess deaths from the pandemic during 2020 and 2021, again concluding ≈14.8 million excess early deaths occurred, reaffirming and detailing their prior calculations from May as well as updating them, addressing criticisms. These numbers do not include measures like years of potential life lost and may make the pandemic 2021's leading cause of death.
The time between symptom onset and death ranges from6 to 41 days, typically about 14 days. Mortality rates increase as a function of age. People at the greatest mortality risk are the elderly and those with underlying conditions.