Influenza, Pandemic, 1918


Immunology of Infectious Disease | Virology


The 1918 Influenza outbreak is regarded as one of the worst pandemics in human history due to its widespread effects across the globe and its high death rate. This death rate was unusual among influenza infections as most strains do not cause the amount of death that is seen in this outbreak, with 20 million dead as a conservative estimate and 100 million by other estimations. This pandemic was not very well contained for a plethora of reasons. Two main reasons are that it came at a time when understanding viral mechanics still escaped medical professionals, and due to the ongoing war quarantine was not a measure imposed by many cities. To understand how this virus was able to so effectively wreak havoc in the human population, it must be shown how this virus was unique not just in spread, but also in its method of killing its host. These two traits must be looked at together as the virus was able to spread so quickly and this virus was able to kill not just those with a weak immune system, but in many cases those individuals who had the best immune system to fight the infection still died from the disease. The virus was able to be so effective at spreading and causing death, due to alterations to its genome which allowed both for an asymptomatic period of the infection where the PA gene was used as a less pathogenic version (PA-X) this allowed the virus to multiply to a point where it could easily overwhelm total body defense with number of viral particles. This asymptomatic period allowed the viral transmission to spread faster than people expected as the virus would be transmitted before an infected individual knew they were sick. This allowed for another unique trait of the virus to take over, the cytokine storm. This storm used the body’s own defenses to weaken it and paralyze the immune system in a way that allowed for a secondary infection to easily infect the host and cause death. This happened during this pandemic as many of those who died fell to a bacterial pneumonia infection and not the virus itself. These characteristics, combined with the virus’ timing allowed for it to be the worst pandemic that mankind had experienced. As the virus both exhibited novel traits, and came at a time when preventative measures were not in place and human migration was occurring due to the war.