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This is what H1N1 patient zero looks like 11 years after the outbreak 2:38
(CNN Spanish) - The World Health Organization (WHO) declared this Wednesday that the outbreak of the new coronavirus, with an epicenter in Wuhan, China, is already a pandemic.
A pandemic is the "worldwide spread" of a new disease.
These have been part of human history for centuries, and one of the earliest in history dates back to 1580. Since then, at least four influenza pandemics occurred in the 19th century and three in the 20th century, according to the Centers. for US Disease Control and Prevention (CDC).
An announcement from the Buenos Aires city government gives advice on how to avoid becoming infected with the A (H1N1) influenza virus, at a metro station in Buenos Aires on July 7, 2009. (JUAN MABROMATA / AFP via Getty Images )
The last pandemic declared by the WHO was the influenza A H1N1 virus.
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Chronology
This is how the A H1N1 virus developed according to the CDC:
April 15, 2009: The first case of human infection with influenza A H1N1 virus is detected in California.
April 25, 2009: The WHO declared a state of public health emergency of international interest.
April 27, 2009: WHO Director-General stepped up the alert level for an influenza pandemic from phase 3 to phase 4, according to data showing person-to-person spread and the ability of the virus to cause outbreaks in communities.
April 29, 2009: WHO stepped up the alert level for an influenza pandemic from phase 4 to phase 5 to indicate that a pandemic was imminent and requested that all countries immediately activate their pandemic preparedness plans and be alert to rare outbreaks of influenza-like illness and severe pneumonia.
Summer 2009 H1N1 influenza virus activity peaked in the United States during May and June.
June 11, 2009: The WHO declared the pandemic and raised the global pandemic alert level to Phase 6 indicating that the virus was spreading in other parts of the world.
September 15, 2009: The FDA announced the approval of four 2009 H1N1 influenza vaccines.
Dosages of the H1N1 influenza vaccine are shown at Carlin Springs Elementary School on January 7, 2010 in Arlington, Virginia. (Photo by Win McNamee / Getty Images)
The second wave of H1N1 influenza activity peaked in the US. USA in late October 2009 .
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In January 2010, activity decreased below the reference level, but persisted for several months with low levels.
August 11, 2010: The WHO announced the end of the 2009 H1N1 influenza pandemic.
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The United States estimated that 151,700 to 575,400 people worldwide died from infection with the influenza virus (H1N1) pdm09, known as A H1N1, during the virus' first year of circulation.
Globally, it was estimated that 80% of influenza virus-related deaths occurred among people under the age of 65.
Moderna sent its coronavirus vaccine for testing.
The most serious pandemic in recent history was the 1918 flu, sometimes called the "Spanish flu." It is estimated to have infected about 500 million people or a third of the world's population and killed some 50 million worldwide.
AH1N1 Pandemic