Portal:Pandemics
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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 human immunodeficiency virus (HIV) is a retrovirus that attacks the immune system. It is a preventable disease. There is no vaccine or cure for HIV. It can be managed with treatment and become a manageable chronic health condition. While there is no cure or vaccine, antiretroviral treatment can slow the course of the disease and enable people living with HIV to lead long and healthy lives. An HIV-positive person on treatment can expect to live a normal life, and die with the virus, not of it. Effective treatment for HIV-positive people (people living with HIV) involves a life-long regimen of medicine to suppress the virus, making the viral load undetectable. Without treatment it can lead to a spectrum of conditions including acquired immunodeficiency syndrome (AIDS).
Treatment is recommended as soon as the diagnosis is made. An HIV-positive person who has an undetectable viral load as a result of long-term treatment has effectively no risk of transmitting HIV sexually. Campaigns by UNAIDS and organizations around the world have communicated this as Undetectable = Untransmittable. Without treatment the infection can interfere with the immune system, and eventually progress to AIDS, sometimes taking many years. Following initial infection an individual may not notice any symptoms, or may experience a brief period of influenza-like illness. During this period the person may not know that they are HIV-positive, yet they will be able to pass on the virus. Typically, this period is followed by a prolonged incubation period with no symptoms. Eventually the HIV infection increases the risk of developing other infections such as tuberculosis, as well as other opportunistic infections, and tumors which are rare in people who have normal immune function. The late stage is often also associated with unintended weight loss. Without treatment a person living with HIV can expect to live for 11 years. Early testing can show if treatment is needed to stop this progression and to prevent infecting others. (Full article...) -
Indigenous victims (likely smallpox), Florentine Codex (compiled 1540–1585)
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 Naples Plague was an epidemic of plague in the Kingdom of Naples, lasting from 1656 to 1658. The epidemic affected mostly Central Italy and Southern Italy, killing up to 1,250,000 people throughout the Kingdom of Naples according to some estimates.
In the city of Naples alone, approximately 150,000–200,000 people died in 1656 due to the plague, accounting for more than half of the population. The epidemic had a severe impact on the economic and social structure of Naples and some other affected areas. (Full article...) -
A plague doctor and his typical apparel during the 17th century
The second plague pandemic was a major series of epidemics of plague that started with the Black Death, which reached medieval Europe in 1346 and killed up to half of the population of Eurasia in the next four years. It followed the first plague pandemic that began in the 6th century with the Plague of Justinian, but had ended in the 8th century. Although the plague died out in most places after 1353, it became endemic and recurred regularly. A series of major epidemics occurred in the late 17th century, and the disease recurred in some places until the late 18th century or the early 19th century. After this, a new strain of the bacterium gave rise to the third plague pandemic, which started in Asia around the mid-19th century.
Plague is caused by the bacterium Yersinia pestis, which exists in parasitic fleas of several species in the wild and of rats in human society. In an outbreak, it may kill all of its immediate hosts and thus die out, but it can remain active in other hosts that it does not kill, thereby causing a new outbreak years or decades later. (Full article...) -
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 being the 1918–1920 Spanish flu pandemic and the second being the 1977 Russian flu). 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".
Unlike most strains of influenza, the pandemic H1N1/09 virus did not disproportionately infect adults older than 60 years; this was an unusual and characteristic feature of the H1N1 pandemic. Even in the case of previously healthy people, a small percentage develop pneumonia or acute respiratory distress syndrome (ARDS). This manifests itself as increased breathing difficulty and typically occurs three to six days after initial onset of flu symptoms. The pneumonia caused by flu can be either direct viral pneumonia or a secondary bacterial pneumonia. A November 2009 New England Journal of Medicine article recommended that flu patients whose chest X-ray indicates pneumonia receive both antivirals and antibiotics. In particular, it is a warning sign if a child seems to be getting better and then relapses with high fever, as this relapse may be bacterial pneumonia. (Full article...) -
The COVID-19 pandemic (also known as the coronavirus pandemic and COVID pandemic), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), began with an outbreak of COVID-19 in Wuhan, China, in December 2019. It 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 as having become a pandemic on 11 March.
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. COVID-19 vaccines were developed rapidly and deployed to the general public beginning in December 2020, made available through government and international programs 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. (Full article...) -
Saint Sebastian pleading for the life of a gravedigger afflicted with plague during the 7th-century Plague of Pavia, by South Netherlandish painter Josse Lieferinxe ca. 1498
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...) -
Smallpox was an infectious disease caused by variola virus (often called smallpox virus), which belongs to the genus Orthopoxvirus. The last naturally occurring case was diagnosed in October 1977, and the World Health Organization (WHO) certified the global eradication of the disease in 1980, making smallpox the only human disease to have been eradicated to date.
The initial symptoms of the disease included fever and vomiting. This was followed by formation of ulcers in the mouth and a skin rash. Over a number of days, the skin rash turned into the characteristic fluid-filled blisters with a dent in the center. The bumps then scabbed over and fell off, leaving scars. The disease was transmitted from one person to another primarily through prolonged face-to-face contact with an infected person or rarely via contaminated objects. Prevention was achieved mainly through the smallpox vaccine. Once the disease had developed, certain antiviral medications could potentially have helped, but such medications did not become available until after the disease was eradicated. The risk of death was about 30%, with higher rates among babies. Often, those who survived had extensive scarring of their skin, and some were left blind. (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 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...) -
Example of an epidemic showing the number of new infections over time.
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. (Full article...) -
The Antonine Plague of AD 165 to 180, also known as the Plague of Galen (after Galen, the Greek physician who described it), was a prolonged and destructive epidemic, which impacted the Roman Empire. It was possibly contracted and spread by soldiers who were returning from campaign in the Near East. Scholars generally believed the plague was smallpox, due to the skin eruptions over the entirety of the body which appeared to be red and black (Horgan), although measles has also been suggested, and recent genetic evidence strongly suggests that the most severe form of smallpox arose in Europe much later. As yet, there is no genetic evidence from the Antonine plague.
Ancient sources agree that the plague is likely to have appeared during the Roman siege of the Mesopotamian city of Seleucia in the winter of 165–166, during the Parthian campaign of Lucius Verus. Ammianus Marcellinus reported that the plague spread to Gaul and to the legions along the Rhine. Eutropius stated that a large proportion of the empire's population died from this outbreak. According to the contemporary Roman historian Cassius Dio, the disease broke out again nine years later in 189 AD and caused up to 2,000 deaths a day in the city of Rome, 25% of those who were affected. The total death count has been estimated at 5–10 million, roughly 10% of the population of the empire. The disease was particularly deadly in the cities and within the Roman army. (Full article...) -
Colored Scanning electron microscope (SEM) image of SARS-CoV-2, speculated in 2020 as being the first virus to create Disease X
Disease X is a placeholder name that was adopted by the World Health Organization (WHO) in February 2018 on their shortlist of blueprint priority diseases to represent a hypothetical, unknown pathogen that could cause a future epidemic. The WHO adopted the placeholder name to ensure that their planning was sufficiently flexible to adapt to an unknown pathogen (e.g., broader vaccines and manufacturing facilities). Director of the US National Institute of Allergy and Infectious Diseases Anthony Fauci stated that the concept of Disease X would encourage WHO projects to focus their research efforts on entire classes of viruses (e.g., flaviviruses), instead of just individual strains (e.g., zika virus), thus improving WHO capability to respond to unforeseen strains. In 2020, experts, including some of the WHO's own expert advisors, speculated that COVID-19, caused by the SARS-CoV-2 virus strain, met the requirements to be the first Disease X. (Full article...) -
The plague of Justinian or Justinianic plague (AD 541–549) was an epidemic that afflicted the entire Mediterranean Basin, Europe, and the Near East, severely affecting the Sasanian Empire and the Byzantine Empire, especially Constantinople. The plague is named for the Byzantine Emperor Justinian I (r. 527–565), who according to his court historian Procopius contracted the disease and recovered in 542, at the height of the epidemic which killed about a fifth of the population in the imperial capital. The contagion arrived in Roman Egypt in 541, spread around the Mediterranean Sea until 544, and persisted in Northern Europe and the Arabian Peninsula until 549. By 543, the plague had spread to every corner of the empire. As the first episode of the first plague pandemic, it had profound economic, social, and political effects across Europe and the Near East and cultural and religious impact on Eastern Roman society.
In 2013, researchers confirmed earlier speculation that the cause of the plague of Justinian was Yersinia pestis, the same bacterium responsible for the Black Death (1346–1353). Ancient and modern Yersinia pestis strains are closely related to the ancestor of the Justinian plague strain that has been found in the Tian Shan, a system of mountain ranges on the borders of Kyrgyzstan, Kazakhstan, and China, suggesting that the Justinian plague originated in or near that region. However, there would appear to be no mention of bubonic plague in China until the year 610. (Full article...) -
Crimson Contagion was a joint exercise conducted from January to August 2019, in which numerous national, state and local, private and public organizations in the US participated, in order to test the capacity of the federal government and twelve states to respond to a severe pandemic of influenza originating in China.
The simulation, which was conducted by the Department of Health and Human Services in a series of exercises that ran from January to August 2019, involved a scenario in which a group of about 30 tourists returning from China spread a novel influenza A respiratory virus in the United States, beginning in Chicago. In less than two months the virus had spread from a single index case (a 52-year-old man returning to Chicago) to infect 110 million Americans; 7.7 million patients would require hospitalization, and 586,000 people would die from the novel virus. The 70-page report issued at the conclusion of the exercise outlined the government's limited capacity to respond to a pandemic. States experienced "multiple challenges" requesting resources from the federal government "due to a lack of standardized, well-understood, and properly executed resource request processes," the report said. Federal agencies lacked the funds, coordination, and capacities to implement an effective response to the virus. (Full article...)
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General images -
The following are images from various pandemic- and epidemic-related articles on Wikipedia.
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Estimates of hypothetical influenza deaths in the 2010 United States population (308,745,538 persons) across varying values of case-fatality ratio and the cumulative incidence of infection in the population. Selected estimated numbers of deaths are indicated with a black line, across each relevant combination of case-fatality ratio and cumulative incidence. In addition, the background color transitions from blue to yellow to red as the estimated absolute number of deaths increases. Case-fatality ratio is an example of a clinical severity measure and cumulative incidence of infection is an example of a transmissibility measure in the Pandemic Severity Assessment Framework. (from Pandemic Severity Assessment Framework) -
Anopheles mosquito, the vector of malaria (from Epidemic) -
First cholera pandemic (from History of cholera) -
1892 cholera outbreak in Hamburg, hospital ward (from History of cholera) -
By 12 February 2009, the number of cases of infection by cholera in sub-Saharan Africa had reached 128,548 and the number of fatalities, 4,053. (from History of cholera) -
The difference between the influenza mortality age-distributions of the 1918 epidemic and normal epidemics. Deaths per 100,000 persons in each age group, United States, for the interpandemic years 1911–1917 (dashed line) and the pandemic year 1918 (solid line). (from Influenza pandemic) -
A pump memorializing John Snow for his study of contaminated water as a likely source of cholera during the 1854 Broad Street Cholera outbreak (from History of cholera) -
Bodies of Rwandan refugees who died during the cholera epidemic, October 1994 (from History of cholera) -
Influenza intervals in the CDC's Pandemic Intervals Framework (from Influenza pandemic) -
The various types of influenza viruses in humans. Solid squares show the appearance of a new strain, causing recurring influenza pandemics. Broken lines indicate uncertain strain identifications. (from Influenza pandemic) -
Register of Patients Gosport Naval Hospital August 1832 cholera cases (from History of cholera) -
Scaled examples of past influenza pandemics and past influenza seasons. Color scheme included to represent corresponding estimates of hypothetical influenza deaths in the 2010 US population, with the same color scale as the previous figure. (from Pandemic Severity Assessment Framework) -
Disposal of dead bodies during the cholera epidemic in Palermo in 1835 (from History of cholera) -
Influenza ward at Walter Reed Hospital, in Washington, D.C., during the 1918 flu pandemic (from Influenza pandemic) -
The Plague of Athens (c. 1652–1654) by Michiel Sweerts, illustrating the devastating epidemic that struck Athens in 430 BC, as described by the historian Thucydides (from Epidemic) -
Example of an epidemic showing the number of new infections over time. (from Epidemic) -
Possibilities for zoonotic disease transmissions (from Epidemic) -
Patients suffering from cholera in 1854 (from History of cholera) -
Hand bill from the New York City Board of Health, 1832. The outdated public health advice demonstrates the lack of understanding of the disease and its actual causative factors. (from History of cholera) -
Structure of the influenza viron. The hemagglutinin (HA) and neuraminidase (NA) proteins are shown on the surface of the particle. The viral RNAs that make up the genome are shown as red coils inside the particle and bound to Ribonuclear Proteins (RNPs). (from Influenza pandemic)
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