Posted on 28 July 2020
The influenza pandemic of 1918 was one of the most devastating in human history, with some estimating that the( ) virus responsible claimed over 50 million lives around the world. While Spanish may have ended there, it’s easy to forget that the lived on, contributing its genes to new viruses and giving rise to new pandemics.
originated in birds, which form a vast reservoir in which influenza viruses can mutate and exchange the 8 genes that make up their genetic code. This means that a near endless variety of new viruses are constantly being produced.
Thehas a gene coding for 1 of 16 possible haemagglutinin (HA) surface proteins and another coding for 1 of 9 possible neuraminidase (NA) surface proteins. These are critical for the infection of host cells. Of the 144 possible combinations, only 3 have ever been found to infect humans: , , and . While it is rare for an to cross over to humans or other mammals, once it does so, it is highly capable of countering the immunity developed by its host, evolving through mutation (drift) and gene exchange with other circulating viruses (shift).
In this way, thevirus and its descendants have undergone a century of evolution as they have competed against the human immune system. Almost all cases are now caused by descendants of 1918 , from the 2009 to seasonal influenza that most of us experience.
It remains to be seen whether the One study suggests that if duration of immunity to SARS-CoV-2 is similar to other related , then recurrent outbreaks are likely.responsible for the current pandemic will have a similar legacy. While Sars-Cov-2 appears to mutate more slowly than , the likelihood of Covid entering regular circulation alongside other human depends largely on how long immunity lasts, a question that has still not been fully answered.
The Persistent Legacy of the 1918 Influenza Virus: DOI: 10.1056/NEJMp0904819
1918 Influenza: the Mother of All Pandemics: doi: 10.3201/eid1201.050979
Projecting the transmission dynamics of SARS-CoV-2 through the postpandemic period: DOI: 10.1126/science.abb5793