What caused the 1918 pandemic?

Combination of human and swine flu strains.

How do influenza viruses evolve?

Through antigenic drift and shift.

They have influenced every flu pandemic since.

Affected young adults due to lack of prior exposure.

Medical advances, including vaccines and prevention measures.

Influenza A viruses, characterized by their hemagglutinin (HA) and neuraminidase (NA) proteins, are the sole cause of pandemics, with the 1918 H1N1 strain originating from a combination of human H1 and swine N1 strains, leading to a highly infectious variant.
The 1918 H1N1 flu virus, influencing subsequent pandemics and seasonal flu lineages, has left a lasting impact on influenza evolution, emphasizing the critical importance of understanding flu strains and their evolution to prevent future deadly outbreaks, as seen in the 2009 H1N1 "swine flu" outbreak.

What caused the 1918 pandemic?
Combination of human and swine flu strains.
How do influenza viruses evolve?
Through antigenic drift and shift.
What is the significance of the 1918 flu virus genes?
They have influenced every flu pandemic since.
How did the 2009 H1N1 flu outbreak differ from the 1918 pandemic?
Affected young adults due to lack of prior exposure.
What contributed to the lower fatality rate of the 2009 H1N1 flu outbreak?
Medical advances, including vaccines and prevention measures.

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The 1918 H1N1 influenza virus caused the most deadly pandemic of the last century, infecting 500 million people and killing at least 50 million.
Influenza viruses are categorized into types A, B, and C, with A being the only one causing pandemics.
Influenza A viruses are named based on their hemagglutinin (HA) and neuraminidase (NA) proteins, which allow the virus to infect cells.
Influenza A viruses can evolve through antigenic drift, where gradual genetic changes occur, and antigenic shift, where different strains combine.
The 1918 H1N1 flu virus originated from a combination of human H1 and swine N1 strains, leading to a highly infectious strain.
Subsequent pandemics in 1957 and 1968 were also influenced by genes from the 1918 flu virus, resulting in new strains with increased infectivity.
The 1968 H3N2 pandemic, derived from the 1918 H1N1 strain, outcompeted the 1957 H2N2 virus and became one of the two seasonal flu lineages.
The 1918 H1N1 virus transferred back into swine, leading to two distinct lineages: North American and Eurasian.
The 1918 flu virus genes have been circulating in every flu pandemic since, showcasing its lasting impact on influenza evolution.
The 1918 pandemic highlighted the importance of understanding flu strains and their evolution to prevent future deadly outbreaks.

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Swine lineages mixed in Mexico, combining with a human-circulating H3N2 virus to create the 2009 H1N1 "swine flu" outbreak, a triple assortment of avian, swine, and human flus.
The 2009 flu pandemic, similar to the 1918 flu, affected young adults severely due to the lack of circulation of H1N1 flus of this subtype for decades, with older individuals possibly protected by exposure to the H3N2 flu of 1968.
Medical advances, including vaccines and improved virus spread prevention, contributed to the lower fatality rate of the 2009 H1N1 flu outbreak compared to previous pandemics.
Researchers are exploring the concept of original antigenic sin in influenza outcomes to potentially develop more effective, universal influenza vaccines, with attention shifting to the H5N1 strain as a possible successor to the 2009 H1N1 flu.