# 4698
The 1918 Spanish Flu was the worst pandemic in modern history, killing (estimates vary) between 40 million and 100 million people worldwide in a matter of 18 months.
The course and impact of the pandemic was reasonably well documented in places like the United States, England, and parts of Europe . . . but for much of the world the death toll can only be approximated.
Earlier studies have suggested a wide variation in the CFR (Case Fatality Ratio) of this pandemic among various countries and regions of the world.
In 2006, in a Lancet journal (doi:10.1016/S0140- 6736(06) 69895-4) article cited as much as a 30-fold difference in mortality rates around the world:
Christopher JL Murray , Alan D Lopez , Brian Chin , Dennis Feehan , Kenneth H Hill
Excess mortality ranged from 0·2% in Denmark to 4·4% in India. Since there was some under-registration of mortality in India, total pandemic mortality could have been even higher.
One of the striking features of the 1918 pandemic – aside from the high death toll – was the sparing of those over the age of 65 in the United States.
The infamous `W shaped curve’ of the 1918 pandemic clearly shows that the death rates among those in their teens, 20s, and 30s was much higher than was normally seen in previous influenza years.
Those over the age of 65, however, saw a reduction in mortality during the pandemic.
A situation not unlike what we saw last year with few over the age of 60 contracting the 2009 H1N1 pandemic virus.
We’ve a new study, appearing in the Journal of Infectious Diseases that suggests that the course of the 1918 pandemic was different in Mexico than in its immediate neighbor to the north.
That unlike in the United States, those over 65 experienced an increased mortality rate, raising interesting questions regarding geographic differences in pre-existing immunity to the virus.
Since the full article is behind a pay wall, I’ve not read the entire paper. The abstract is available, however.
Hopefully we’ll get a more in depth summary of this paper from another source in the next couple of days. If so, I’ll update this post with a link.
Mortality Patterns Associated with the 1918 Influenza Pandemic in Mexico: Evidence for a Spring Herald Wave and Lack of Preexisting Immunity in Older Populations
Gerardo Chowell, Cécile Viboud, Lone Simonsen, Mark A. Miller, and Rodolfo Acuna‐Soto
Background. Although the mortality burden of the devastating 1918 influenza pandemic has been carefully quantified in the United States, Japan, and European countries, little is known about the pandemic experience elsewhere. Here, we compiled extensive archival records to quantify the pandemic mortality patterns in 2 Mexican cities, Mexico City and Toluca.
Methods. We applied seasonal excess mortality models to age‐specific respiratory mortality rates for 1915–1920 and quantified the reproduction number from daily data.
Results. We identified 3 pandemic waves in Mexico City in spring 1918, autumn 1918, and winter 1920, which were characterized by unusual excess mortality among people 25–44 years old. Toluca experienced 2‐fold higher excess mortality rates than Mexico City but did not experience a substantial third wave. All age groups, including that of people >65 years old, experienced excess mortality during 1918–1920. Reproduction number estimates were <2.5, assuming a 3‐d generation interval.
Conclusion. Mexico experienced a herald pandemic wave with elevated young adult mortality in spring 1918, similar to the United States and Europe. In contrast to the United States and Europe, there was no mortality sparing among Mexican seniors > 65 years old, highlighting potential geographical differences in preexisting immunity to the 1918 virus. We discuss the relevance of our findings to the 2009 pandemic mortality patterns.
