This well known 1918 Flu or Spanish Flu pandemic caused the highest number of known influenza deaths. An estimated one-third of the world’s population (500 million people) became infected and had flu symptoms during the 1918 flu outbreak.
More than 500,000 people died in the United States, and 50 million people or more died worldwide. Many people died within the first few days after infection while others died of complications. Nearly half of those who died were young, healthy adults.
What Caused the 1918 Flu or Spanish Flu Pandemic?
The specific virus that caused the 1918 flu was the influenza A (H1N1) virus, which appears to be an avian-like influenza virus.
How Did the 1918 Flu Pandemic Progressed ?
The 1918 flu pandemic spread more or less simultaneously in 3 distinct waves during a 12-month period from 1918–1919, in Europe, Asia, and North America.
The first pandemic influenza wave appeared in the spring of 1918, followed in rapid succession by much more fatal second and third waves in the fall and winter of 1918–1919, respectively. The 1918 flu pandemic had another unique feature, the simultaneous (or nearly simultaneous) infection of humans and swine.
The Fatality Rate Curve of the 1918 Flu Pandemic
The curve of influenza deaths by age has, generally has been U-shaped, with death peaks in the very young and the very old, with a comparatively low number of deaths at all ages in between.
In contrast, in the 1918 flu pandemic, it showed a distinct pattern that has not been documented before: a “W-shaped” curve, similar to the familiar U-shaped curve but with the addition of a third (middle) distinct peak of deaths in young adults who were between 20 and 40 years of age.
Influenza and pneumonia death rates for those 15 to 34 years of age in 1918–1919, for example, were 20 times higher than in previous years. Surprisingly, nearly half of the influenza-related deaths in the 1918 pandemic were in young adults who were 20 to 40 years of age, a phenomenon very unique.
The 1918 flu pandemic is also unique among influenza pandemics in that risk of influenza death was higher in those who were younger than 65 years of age than in those who were greater than 65 years of age
Prevention and Treatment of the 1918 Flu
Two types of antiviral drugs, rimantadine (Flumadine®) and oseltamivir (Tamiflu®), have been shown to be effective against influenza viruses similar to the 1918 flu virus. Vaccines containing the 1918 flu HA or other subtype H1 HA proteins were effective in protecting mice against the 1918 flu virus
Can the 1918 Flu Pandemic Happen Again ?
The evolutionary path that led to pandemic emergence of the 1918 flu is not known, but it appears to be different in many respects from the current situation with H5N1 (avian flu).
Even with modern antiviral and antibacterial drugs, vaccines, and prevention knowledge, the return of a pandemic virus equivalent in pathogenicity with the 1918 flu would likely kill more than 100 million people worldwide.
This has made experts very worried about this current A(H1N1) flu. Despite symptoms being relatively mild as compared to the avian flu, WHO has warned against complacency.