page_title: Influenza
section_title: Pandemics
hierarchical_section_title: Influenza / History / Pandemics
caption_attribution_description: English: Figure 2. "U-" and "W-" shaped combined influenza and pneumonia mortality, by age at death, per 100,000 persons... Deutsch: Abbildung 2. "U-" und "W-" Kurven der Todesrate von Grippe und Lungenentzündung über dem Todesalter, auf je 100.000 Personen bezogen
context_page_description: Influenza, commonly known as "the flu", is an infectious disease caused by an influenza virus. Symptoms can be mild to severe. The most common symptoms include: high fever, runny nose, sore throat, muscle and joint pain, headache, coughing, and feeling tired. These symptoms typically begin two days after exposure to the virus and most last less than a week. The cough, however, may last for more than two weeks. In children, there may be diarrhea and vomiting, but these are not common in adults. Diarrhea and vomiting occur more commonly in gastroenteritis, which is an unrelated disease and sometimes inaccurately referred to as "stomach flu" or the "24-hour flu". Complications of influenza may include viral pneumonia, secondary bacterial pneumonia, sinus infections, and worsening of previous health problems such as asthma or heart failure.
  Three of the four types of influenza viruses affect humans: Type A, Type B, and Type C. Type D has not been known to infect humans, but is believed to have the potential to do so. Usually, the virus is spread through the air from coughs or sneezes. This is believed to occur mostly over relatively short distances.
context_section_description: An overall lack of data up until 1500 precludes meaningful search for the influenza outbreaks in the more distant past. Possibly the first influenza pandemic occurred around 6000 BC in China. The symptoms of human influenza were clearly described by Hippocrates roughly 2,400 years ago. Although the virus seems to have caused epidemics throughout human history, historical data on influenza are difficult to interpret, because the symptoms can be similar to those of other respiratory diseases. The disease may have spread from Europe to the Americas as early as the European colonization of the Americas, since almost the entire indigenous population of the Antilles was killed by an epidemic resembling influenza that broke out in 1493, after the arrival of Christopher Columbus.
  The first convincing record of an influenza pandemic was a minor pandemic chronicled in 1510, which began in East Asia before spreading to North Africa and then Europe. During this pandemic, influenza killed about 1% of its victims. The first pandemic of influenza to be reliably recorded as spreading worldwide was the 1557 influenza pandemic, in which a reoccurring wave likely killed Queen Mary I of England and the Archbishop of Canterbury within 12 hours of each other. One of the most well-chronicled pandemics of influenza in the 16th Century occurred in 1580, beginning in East Asia and spreading to Europe through Africa, Russia, and the Spanish and Ottoman Empires. In Rome, over 8,000 people were killed. Several Spanish cities saw large scale deaths, among the fatalities the Queen of Spain, Anna of Austria. Pandemics continued sporadically throughout the 17th and 18th centuries, with the pandemic of 1830–1833 being particularly widespread; it infected approximately a quarter of the people exposed. 
  The most famous and lethal outbreak was the 1918 flu pandemic (Spanish flu) (type A influenza, H1N1 subtype), which lasted into 1920. It is not known exactly how many it killed, but estimates range from 17 million to 100 million people. This pandemic has been described as "the greatest medical holocaust in history" and may have killed as many people as the Black Death. This huge death toll was caused by an extremely high infection rate of up to 50% and the extreme severity of the symptoms, suspected to be caused by cytokine storms. Symptoms in 1918 were so unusual that initially influenza was misdiagnosed as dengue, cholera, or typhoid. One observer wrote, "One of the most striking of the complications was hemorrhage from mucous membranes, especially from the nose, stomach, and intestine. Bleeding from the ears and petechial hemorrhages in the skin also occurred." The majority of deaths were from bacterial pneumonia, a secondary infection caused by influenza, but the virus also killed people directly, causing massive hemorrhages and edema in the lung.
  The 1918 flu pandemic was truly global, spreading even to the Arctic and remote Pacific islands. The unusually severe disease killed between two and twenty percent of those infected, as opposed to the more usual flu epidemic mortality rate of 0.1%. Another unusual feature of this pandemic was that it mostly killed young adults, with 99% of pandemic influenza deaths occurring in people under 65, and more than half in young adults 20 to 40 years old. This is unusual since influenza is normally most deadly to the very young (under age 2) and the very old (over age 70). The total mortality of the 1918–1919 pandemic is not known, but it is estimated that 2.5% to 5% of the world's population was killed. As many as 25 million may have been killed in the first 25 weeks; in contrast, HIV/AIDS has killed 25 million in its first 25 years.
  Later flu pandemics were not so devastating. They included the 1957 Asian flu (type A, H2N2 strain) and the 1968 Hong Kong flu (type A, H3N2 strain), but even these smaller outbreaks killed millions of people. In later pandemics antibiotics were available to control secondary infections and this may have helped reduce mortality compared to the Spanish flu of 1918.
  
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caption: 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).[204]
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