page_title: Virus
section_title: Epidemics and pandemics
hierarchical_section_title: Virus / Role in human disease / Epidemics and pandemics
caption_attribution_description: English: This negative stained transmission electron micrograph (TEM) showed recreated 1918 influenza virions that were collected from the supernatant of a 1918-infected Madin-Darby Canine Kidney (MDCK) cell culture 18 hours after infection. In order to sequester these virions, the MDCK cells were spun down (centrifugation), and the 1918 virus present in the fluid was immediately fixed for negative staining. Dr. Terrence Tumpey, one of the organization’s staff microbiologists and a member of the National Center for Infectious Diseases (NCID), recreated the 1918 influenza virus in order to identify the characteristics that made this organism such a deadly pathogen. Research efforts such as this, enables researchers to develop new vaccines and treatments for future pandemic influenza viruses. The 1918 Spanish flu epidemic was caused by an influenza A (H1N1) virus, killing more than 500,000 people in the United States, and up to 50 million worldwide. The possible source was a newly emerged virus from a swine or an avian host of a mutated H1N1 virus. Many people died within the first few days after infection, and others died of complications later. Nearly half of those who died were young, healthy adults. Influenza A (H1N1) viruses still circulate today after being introduced again into the human population in the 1970s. Deutsch: Virionen des rekonstruierten Virus der spanischen Grippe, 18 Stunden nach Infektion der Kultur. Français&#160;: Virus reconstitué de la grippe espagnole, celui qui est le plus proche par ses effets sur l'organisme du virus H5N1. Photographie électronique du Virus de 1918 rétrospectivement reconstitué par génie génétique à partir d'échantillons de restes humains de 1918. 日本語: 患者の遺体から見つかったゲノムより復元されたスペインかぜウイルス. Italiano: Immagine al microscopio elettronico del virus del 1918 (ricreato in laboratorio). Português: Vírus da gripe espanhola reconstituído. Español: Imagen al microscopio electrónico del virus de 1918 (recreado en laboratorio). 中文: 重建的西班牙流感病毒。. Türkçe: Yeniden yaratılmış 1918 influenza virüsü. Magyar: A spanyolnátha egykori áldozataiból nyert mintából kitenyésztett kórokozó elektronmikroszkópos képe. עברית: מבנה נגיף השפעת הספרדית 한국어: 스페인 독감 바이러스의 사진. Íslenska: Endurgerður vírus sem ræktaður var úr manni sem lést árið 1918. Latina: Imago cum microscopio viri. Sunda: Wangun ulang virus flu 1918.
context_page_description: A virus is a submicroscopic infectious agent that replicates only inside the living cells of an organism. Viruses infect all types of life forms, from animals and plants to microorganisms, including bacteria and archaea.
  Since Dmitri Ivanovsky's 1892 article describing a non-bacterial pathogen infecting tobacco plants, and the discovery of the tobacco mosaic virus by Martinus Beijerinck in 1898, more than 6,000 virus species have been described in detail, of the millions of types of viruses in the environment. Viruses are found in almost every ecosystem on Earth and are the most numerous type of biological entity. The study of viruses is known as virology, a subspeciality of microbiology.
  When infected, a host cell is forced to rapidly produce thousands of identical copies of the original virus.
context_section_description: A pandemic is a worldwide epidemic. The 1918 flu pandemic, which lasted until 1919, was a category 5 influenza pandemic caused by an unusually severe and deadly influenza A virus. The victims were often healthy young adults, in contrast to most influenza outbreaks, which predominantly affect juvenile, elderly, or otherwise-weakened patients. Older estimates say it killed 40–50 million people, while more recent research suggests that it may have killed as many as 100 million people, or 5% of the world's population in 1918.
  Although viral pandemics are rare events, HIV—which evolved from viruses found in monkeys and chimpanzees—has been pandemic since at least the 1980s. During the 20th century there were four pandemics caused by influenza virus and those that occurred in 1918, 1957 and 1968 were severe. Most researchers believe that HIV originated in sub-Saharan Africa during the 20th century; it is now a pandemic, with an estimated 37.9 million people now living with the disease worldwide. There were about 770,000 deaths from AIDS in 2018. The Joint United Nations Programme on HIV/AIDS (UNAIDS) and the World Health Organization (WHO) estimate that AIDS has killed more than 25 million people since it was first recognised on 5 June 1981, making it one of the most destructive epidemics in recorded history. In 2007 there were 2.7 million new HIV infections and 2 million HIV-related deaths.
  Several highly lethal viral pathogens are members of the Filoviridae. Filoviruses are filament-like viruses that cause viral hemorrhagic fever, and include ebolaviruses and marburgviruses. Marburg virus, first discovered in 1967, attracted widespread press attention in April 2005 for an outbreak in Angola. Ebola virus disease has also caused intermittent outbreaks with high mortality rates since 1976 when it was first identified. The worst and most recent one is the 2013–2016 West Africa epidemic.
  With the exception of smallpox, most pandemics are caused by newly evolved viruses. These "emergent" viruses are usually mutants of less harmful viruses that have circulated previously either in humans or other animals.
  Severe acute respiratory syndrome (SARS) and Middle East respiratory syndrome (MERS)  are caused by new types of coronaviruses. Other coronaviruses are known to cause mild infections in humans, so the virulence and rapid spread of SARS infections—that by July 2003 had caused around 8,000 cases and 800 deaths—was unexpected and most countries were not prepared.
  A related coronavirus emerged in Wuhan, China in November 2019 and spread rapidly around the world. Thought to have originated in bats and subsequently named severe acute respiratory syndrome coronavirus 2, infections with the virus caused a pandemic in 2020. Unprecedented restrictions in peacetime have been placed on international travel, and curfews imposed in several major cities worldwide.
caption: Transmission electron microscope image of a recreated 1918 influenza virus
exif: {}