A pandemic is an epidemic of an infectious disease that has spread across a large region, for instance multiple continents or worldwide, affecting a substantial number of individuals. Widespread endemic diseases with a stable number of infected individuals such as recurrences of seasonal influenza are generally excluded as they occur simultaneously in large regions of the globe rather than being spread worldwide.
A zoonosis or zoonotic disease is an infectious disease of humans caused by a pathogen that can jump from a non-human to a human and vice versa.
An epidemic is the rapid spread of disease to a large number of hosts in a given population within a short period of time. For example, in meningococcal infections, an attack rate in excess of 15 cases per 100,000 people for two consecutive weeks is considered an epidemic.
Incubation period is the time elapsed between exposure to a pathogenic organism, a chemical, or radiation, and when symptoms and signs are first apparent. In a typical infectious disease, the incubation period signifies the period taken by the multiplying organism to reach a threshold necessary to produce symptoms in the host.
The 1918–1920 flu pandemic, also known as the Great Influenza epidemic or by the common misnomer Spanish flu, was an exceptionally deadly global influenza pandemic caused by the H1N1 influenza A virus. The earliest documented case was March 1918 in the state of Kansas in the United States, with further cases recorded in France, Germany and the United Kingdom in April. Two years later, nearly a third of the global population, or an estimated 500 million people, had been infected in four successive waves. Estimates of deaths range from 17 million to 50 million, and possibly as high as 100 million, making it one of the deadliest pandemics in history.
Swine influenza is an infection caused by any of several types of swine influenza viruses. Swine influenza virus (SIV) or swine-origin influenza virus (S-OIV) refers to any strain of the influenza family of viruses that is endemic in pigs. As of 2009, identified SIV strains include influenza C and the subtypes of influenza A known as H1N1, H1N2, H2N1, H3N1, H3N2, and H2N3.
An influenza pandemic is an epidemic of an influenza virus that spreads across a large region and infects a large proportion of the population. There have been six major influenza epidemics in the last 140 years, with the 1918 flu pandemic being the most severe; this is estimated to have been responsible for the deaths of 50–100 million people. The 2009 swine flu pandemic resulted in under 300,000 deaths and is considered relatively mild. These pandemics occur irregularly.
The 2009 swine flu pandemic, caused by the H1N1/swine flu/influenza virus and declared by the World Health Organization (WHO) from June 2009 to August 2010, was the third recent flu pandemic involving the H1N1 virus. The first identified human case was in La Gloria, Mexico, a rural town in Veracruz. The virus appeared to be a new strain of H1N1 that resulted from a previous triple reassortment of bird, swine, and human flu viruses which further combined with a Eurasian pig flu virus, leading to the term "swine flu".
Influenza prevention involves taking steps that one can use to decrease their chances of contracting flu viruses, such as the Pandemic H1N1/09 virus, responsible for the 2009 flu pandemic.
The 1889–1890 pandemic, often referred to as the "Asiatic flu" or "Russian flu", was a worldwide respiratory viral pandemic. It was the last great pandemic of the 19th century, and is among the deadliest pandemics in history. The pandemic killed about 1 million people out of a world population of about 1.5 billion. The most reported effects of the pandemic took place from October 1889 to December 1890, with recurrences in March to June 1891, November 1891 to June 1892, the northern winter of 1893–1894, and early 1895.
Novel coronavirus (nCoV) is a provisional name given to coronaviruses of medical significance before a permanent name is decided upon. Although coronaviruses are endemic in humans and infections normally mild, such as the common cold, cross-species transmission has produced some unusually virulent strains which can cause viral pneumonia and in serious cases even acute respiratory distress syndrome and death.
John Brownstein is a Canadian epidemiologist and Professor of Medicine at the Harvard Medical School as well as the Chief Innovation Officer at Boston Children’s Hospital. His research focuses on development of computational methods in epidemiology for applications to public health also known as computational epidemiology or e-epidemiology He is also the founder of several global public health surveillance systems including HealthMap. He is most known for his work on global tracking of disease outbreaks.
Severe acute respiratory syndrome coronavirus 2 (SARS‑CoV‑2) is a strain of coronavirus that causes COVID-19, the respiratory illness responsible for the COVID-19 pandemic. The virus previously had the provisional name 2019 novel coronavirus (2019-nCoV), and has also been called human coronavirus 2019. First identified in the city of Wuhan, Hubei, China, the World Health Organization designated the outbreak a public health emergency of international concern from January 30, 2020, to May 5, 2023. SARS‑CoV‑2 is a positive-sense single-stranded RNA virus that is contagious in humans.
Neil Morris Ferguson is a British epidemiologist and professor of mathematical biology, who specialises in the patterns of spread of infectious disease in humans and animals. He is the director of the Jameel Institute, and of the MRC Centre for Global Infectious Disease Analysis, and head of the Department of Infectious Disease Epidemiology in the School of Public Health and Vice-Dean for Academic Development in the Faculty of Medicine, all at Imperial College London.
Cécile Viboud is a Staff Scientist based in the Fogarty International Center at the National Institutes of Health, where she is part of the Multinational Influenza Seasonal Mortality Study (MISMS). Viboud specialises in the mortality of infectious disease. Viboud was involved with epidemiological analysis during the COVID-19 pandemic.
The Central Epidemic Command Center is an agency of the National Health Command Center (NHCC). It has been activated by the government of Taiwan for several disease outbreaks, such as the 2009 swine flu pandemic and the COVID-19 pandemic. The head of the agency is Chen Shih-chung, the minister of health and welfare. The CECC is associated with the Taiwan Centers for Disease Control.
The pneumonia of unknown etiology (PUE) surveillance system is a Chinese monitoring system, established in response to the 2002–2004 SARS outbreak to track emerging respiratory infections, including avian flu and SARS. On 29 December 2019, local hospitals in Wuhan, Hubei Province, China, identified four closely related people, linked to a local wet market, as having a “pneumonia of unknown etiology” using the national system. Their illness was later confirmed as COVID-19 due to SARS-CoV-2.
This article documents the chronology and epidemiology of SARS-CoV-2 in 2019, the virus that causes coronavirus disease 2019 (COVID-19) and is responsible for the COVID-19 pandemic. The first human cases of COVID-19 known to have been identified were in Wuhan, Hubei, China, in December 2019. It marked the beginning of the 2019–2020 COVID-19 outbreak in mainland China.
Helen Y. Chu is an American immunologist who is an assistant professor of medicine at the University of Washington. Her research considers maternal immunization, with a focus on influenza and respiratory syncytial virus. During the COVID-19 pandemic, Chu was the first physician to recognise community transmission of the coronavirus disease within the United States.
Human-to-human transmission (HHT) is an epidemiologic vector, especially in case the disease is borne by individuals known as superspreaders. In these cases, the basic reproduction number of the virus, which is the average number of additional people that a single case will infect without any preventative measures, can be as high as 203.9. Interhuman transmission is a synonym for HHT.
