Portal:Pandemics
The Pandemics and Epidemics Portal

A pandemic (/pænˈdɛmɪk/ pan-DEM-ik) is an epidemic of an infectious disease that has a sudden increase in cases and spreads 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.
Throughout human history, there have been a number of pandemics of diseases such as smallpox. The Black Death, caused by the Plague, caused the deaths of up to half of the population of Europe in the 14th century. The term pandemic had not been used then, but was used for later epidemics, including the 1918 H1N1 influenza A pandemic—more commonly known as the Spanish flu—which is the deadliest pandemic in history. The most recent pandemics include the HIV/AIDS pandemic, the 2009 swine flu pandemic and the COVID-19 pandemic. Almost all these diseases still circulate among humans though their impact now is often far less.
In response to the COVID-19 pandemic, 194 member states of the World Health Organization began negotiations on an International Treaty on Pandemic Prevention, Preparedness and Response, with a requirement to submit a draft of this treaty to the 77th World Health Assembly during its 2024 convention. Further, on 6 May 2024, the White House released an official policy to more safely manage medical research projects involving potentially hazardous pathogens, including viruses and bacteria, that may pose a risk of a pandemic. (Full article...)

An epidemic (from Greek ἐπί epi "upon or above" and δῆμος demos "people") 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.
Epidemics of infectious disease are generally caused by several factors including a change in the ecology of the host population (e.g., increased stress or increase in the density of a vector species), a genetic change in the pathogen reservoir or the introduction of an emerging pathogen to a host population (by movement of pathogen or host). Generally, an epidemic occurs when host immunity to either an established pathogen or newly emerging novel pathogen is suddenly reduced below that found in the endemic equilibrium and the transmission threshold is exceeded.
An epidemic may be restricted to one location; however, if it spreads to other countries or continents and affects a substantial number of people, it may be termed as a pandemic. The declaration of an epidemic usually requires a good understanding of a baseline rate of incidence; epidemics for certain diseases, such as influenza, are defined as reaching some defined increase in incidence above this baseline. A few cases of a very rare disease may be classified as an epidemic, while many cases of a common disease (such as the common cold) would not. An epidemic can cause enormous damage through financial and economic losses in addition to impaired health and loss of life. (Full article...)
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The history of smallpox in Mexico spans approximately 430 years from the arrival of the Spanish to the official eradication in 1951. It was brought to what is now Mexico by the Spanish, then spread to the center of Mexico, where it became a significant factor in the fall of Tenochtitlan. During the colonial period, there were major epidemic outbreaks which led to the implementation of sanitary and preventive policy. The introduction of smallpox vaccination in New Spain by Francisco Javier de Balmis and the work of Ignacio Bartolache reduced the mortality and morbidity of the disease. (Full article...)

The Italian plague of 1629–1631, also referred to as the Great Plague of Milan, was part of the second plague pandemic that began with the Black Death in 1348 and ended in the 18th century. One of two major outbreaks in Italy during the 17th century, it affected northern and central Italy and resulted in at least 280,000 deaths, with some estimating fatalities as high as one million, or about 35% of the population. The plague may have contributed to the decline of Italy's economy relative to those of other Western European countries. (Full article...)

The first plague pandemic was the first historically recorded Old World pandemic of plague, the contagious disease caused by the bacterium Yersinia pestis. Also called the early medieval pandemic, it began with the Plague of Justinian in 541 and continued until 750 or 767. At least fifteen to eighteen major waves of plague following the Justinianic plague have been identified from historical records. The pandemic affected the Mediterranean Basin most severely and most frequently, but also infected the Near East and Northern Europe, and potentially East Asia as well. The Roman emperor Justinian I's name is sometimes applied to the whole series of plague epidemics in late antiquity.
The pandemic is best known from its first and last outbreaks: the Justinianic Plague of 541–549, described by the contemporary Roman historian Procopius, and the late 8th century plague of Naples described by Neapolitan historian John the Deacon in the following century (distinct from the much later Naples Plague). Other accounts from contemporaries of the pandemic are included in the texts of Evagrius Scholasticus, John of Ephesus, Gregory of Tours, Paul the Deacon, and Theophanes the Confessor; most seem to have believed plague was a divine punishment for human misdeeds. (Full article...)

An outbreak of cholera began in Yemen in October 2016. The outbreak peaked in 2017 with over 2,000 reported deaths in that year alone. In 2017 and 2019, war-torn Yemen accounted for 84% and 93% of all cholera cases in the world, with children constituting the majority of reported cases. As of November 2021, there have been more than 2.5 million cases reported, and more than 4,000 people have died in the Yemen cholera outbreak, which the United Nations deemed the worst humanitarian crisis in the world at that time. However, the outbreak has substantially decreased by 2021, with a successful vaccination program implemented and only 5,676 suspected cases with two deaths reported between January 1 and March 6 of 2021.
Vulnerable to water-borne diseases before the conflict, 16 months went by before a program of oral vaccines was started. The cholera outbreak was worsened as a result of the ongoing civil war and the Saudi Arabian-led intervention in Yemen against the Houthi movement that began in March 2015. Airstrikes damaged hospital infrastructure, and water supply and sanitation in Yemen were affected by the ongoing conflict. The government of Yemen stopped funding public health in 2016; sanitation workers were not paid by the government, causing garbage to accumulate, and healthcare workers either fled the country or were not paid. (Full article...)
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 (0.067% of population). 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.
According to researchers' estimates, excess mortality from Russian influenza in the Russian Empire for the period 1889–1890 could be from 60,000 to 90,000 people, with lethality from the virus, a little more than 0.2%. (Full article...)
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 subtype of the influenza A virus. The earliest documented case was March 1918 in Kansas, 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. Estimates of deaths range from 17 million to 50 million, and possibly as high as 100 million, making it the deadliest pandemic in history.
The pandemic broke out near the end of World War I, when wartime censors in the belligerent countries suppressed bad news to maintain morale, but newspapers freely reported the outbreak in neutral Spain, creating a false impression of Spain as the epicenter and leading to the "Spanish flu" misnomer. Limited historical epidemiological data make the pandemic's geographic origin indeterminate, with competing hypotheses on the initial spread. (Full article...)

The Cocoliztli Epidemic or the Great Pestilence was an outbreak of a mysterious illness characterized by high fevers and bleeding which caused 5–15 million deaths in New Spain during the 16th century. The Aztec people called it cocoliztli, Nahuatl for pestilence. It ravaged the Mexican highlands in epidemic proportions, resulting in the demographic collapse of some Indigenous populations.
Based on the death toll, this outbreak is often referred to as the worst epidemic in the history of Mexico. Subsequent outbreaks continued to baffle both Spanish and native doctors, with little consensus among modern researchers on the pathogenesis. However, recent bacterial genomic studies have suggested that Salmonella, specifically a serotype of Salmonella enterica known as Paratyphi C, was at least partially responsible for this initial outbreak. Others believe cocoliztli was caused by an indigenous viral hemorrhagic fever, perhaps exacerbated by the worst droughts to affect that region in 500 years and poor living conditions for Indigenous peoples of Mexico following the Spanish conquest (c. 1519). (Full article...)
The third plague pandemic was a major bubonic plague pandemic that began in Yunnan, China, in 1855. This episode of bubonic plague spread to all inhabited continents, and ultimately led to more than 12 million deaths in India and China (and perhaps over 15 million worldwide), and at least 10 million Indians were killed in British Raj India alone, making it one of the deadliest pandemics in history. According to the World Health Organization, the pandemic was considered active until 1960, when worldwide casualties dropped to 200 per year. Plague deaths have continued at a lower level for every year since.
The name refers to the third of at least three known major plague pandemics. The first began with the Plague of Justinian, which ravaged the Byzantine Empire and surrounding areas in 541 and 542; the pandemic persisted in successive waves until the middle of the 8th century. The second began with the Black Death, which killed at least one third of Europe's population in a series of expanding waves of infection from 1346 to 1353; this pandemic recurred regularly until the 19th century. (Full article...)
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