# 1169
The difference between a pandemic, and nearly any other disaster you can think of is, a pandemic could still be going strong after 18 months.
We don't actually know how long a pandemic can last, but we do know the Spanish Flu of 1918 lasted at least 18 months. I say `at least' because there is at least some evidence it may have lasted longer.
Much longer.
Before the pandemic erupted in the spring of 1918 there were reports of a killer flu appearing in clusters in Europe. The CFR was 50% (sound familiar?), and victims often died quickly and displayed a peculiar form of cyanosis, what would come to be known as heliotrope cyanosis, during the pandemic of 1918.
These reports began as early as 1915. But the world was at war, and a few clusters of deadly pneumonia scarcely attracted notice.
In the Annual Report of the Secretary of the Navy from 1919, excerpts that may be found here, we learn that the incidence of a similar flu had been widely reported in various parts of the world in the years preceding 1918.
Quoting excerpts (reformatted for readability):
Prevalence of Influenza in Recent Years.
Influenza appears to have become unusually prevalent again in the United States at least as early as 1916, when the death rate from this cause in the registration area was 26.4 per 100,000. This was an increase of 65 per cent over the rate for 1915, which was 75 per cent higher than that for 1914.
<snip>
The report of the registrar general of England and Wales for the year 1916 shows that the numbers of deaths from influenza reported by years from 1911 were as follows;
1911 4,334
1912 5,352
1913 6,387
1914 5,953
1915 10,471
1916 8,782
Thus the number of deaths reported in 1915 was nearly double that for preceding years.
Influenza was epidemic in various parts of Europe throughout 1918, and undoubtedly the earlier outbreaks were carried over from 1917.
The files of The Lancet indicate that a more or less widespread epidemic occurred in England in the spring of 1915. The disease does not appear to have been as prevalent in 1916 as in 1915, but in 1917, among the military forces, cases of so-called "purulent bronchitis" occurred which were fundamentally the same as the rapidly fatal cases of influenzal pneumonia so frequently seen at the height of the pandemic.
An epidemic of purulent bronchitis was reported from a British Army base in northern France in January, 1917, whilst an epidemic of influenza was in progress. This outbreak began in December, 1916. Later, in the spring of 1917, similar cases of purulent bronchitis were treated at Aldershot, England.
These cases are noteworthy because they seem to have been similar in all respects to the fatal types of influenzal pneumonia so commonly seen in all parts of the world during the autumn of 1918.
The epidemic referred to was reported by Hammond, Rolland, and Shore in The Lancet, July 14, 1917. They remark that although the earlier cases were admitted during December, 1916, it was not until the end of the following January, when exceptional cold prevailed, that the disease assumed epidemic proportions.
The disease was very fatal and was the cause of death in 45.5 per cent of 156 consecutive cases coming to necropsy. Clinically, the prominent signs were the characteristic yellow purulent or mucopurulent sputum, tachycardia, and cyanosis. The pathological findings were thick purulent material in the smaller bronchi from which frequently air was excluded; in some cases secondary broncho-pneumonia, edema, and emphysema. The lungs were almost always bulky.
<snip>
Abrahams, Hallows, Eyre, and French in The Lancet, September 8, 1917, reported their observations of scores of similar cases in the Aldershot command. Their conclusions were almost identical with those recorded above. Case fatality rates were approximately 50 per cent. Stress was laid upon a peculiar dusky heliotrope type of cyanosis of the face, lips, and ears, as a characteristic sign.
It would appear then that localized outbreaks of a particularly severe form of influenza were occurring at least 3 years (and probably more) before the pandemic of 1918, and this flu carried with it a very high mortality rate. The descriptions of the most critical patients, the heliotrope cyanosis, match the descriptions of patients that would emerge from the 1918 Spanish Flu.
What we cannot know with certainty is whether these earlier outbreaks were the H1N1 virus that caused the Spanish flu. We didn’t even understand that influenza was caused by a virus back then, and had no method of testing.
Still, the evidence points to a much earlier beginning to this pandemic strain of influenza, and that the `pandemic years’ of 1918-1919 were simply the peak years of a longer event.
Just at the lead up to the 1918 outbreak appears to have been longer than previously thought, the end of the pandemic may not have been as abrupt as commonly thought.
In this extract from:
REVIEW AND STUDY OF ILLNESS AND MEDICAL CARE WITH SPECIAL REFERENCE TO LONG-TIME TRENDS
Public Health Monograph No. 48, 1957 (Public Health Service Publication No. 544) by SELWYN D. COLLINS, Ph.D.
Published in 1957, we find this chart showing the Excess annual death rates from influenza and pneumonia in the population of various States and groups of cities in the United States, 1887-1956.
(click to enlarge)
At the top level of the chart, the pandemic of 1889-1890 is clearly represented. Another significant spike in influenza occurred in the 1899-1900 period, although the scale is different on this chart, and the spike is not nearly as high as in 1889.
Influenza like illnesses were on the decline for the next 15 years but began to bubble up again in 1915 and again in 1917. It should be noted that these numbers are from 35 large cities in the United States, and would not necessarily reflect the incidence of influenza in other parts of the world. The Pandemic peaks of 1918-1919 are off the charts.
For the next 10 years, reports of spikes of localized, and severe influenzas occurred around the world, most likely resurgence's of the H1N1 virus. The 4th level of the chart covers the years 1922-1932, and while the scale is roughly half that of the one used in the 1918 strip, it clearly shows sharp, short outbreaks. These numbers come from 90 cities across the United States.
After 1930, influenza in the United States entered a quiescent period which lasted for more than two decades, presumably because our population had acquired herd immunity to the H1N1 strain.
We know that the H1N1 virus remained the dominant strain until the 1957 Asian Flu pandemic, when it acquired genetic changes from an unknown avian strain and changed to the H2N2 strain. While it is thought to have moderated its severity after 1919, it was obviously capable of inflicting much pain and death in susceptible populations after that time.
It appears that the Spanish Flu of 1918 may have been quietly simmering for several years before 1918, and that there were deadly, but localized, outbreaks long after the official end of the pandemic in 1919.
Today we are seeing similar outbreaks to what was seen in the years before 1918. While past performance is not necessarily predictive of future events, it would be foolish to discount a pattern we've seen before.
How the next pandemic will present is unknowable. How long it will last is anyone's guess.
We tend to base our assumptions on a dataset of one, the 1918 pandemic, and expect the next pandemic to act the same. In 1918 we saw waves that lasted for a couple of months, then subsided, only to return months later.
We anticipate the next pandemic will do the same.
But quite frankly, we're all guessing. We haven't enough hard data to go on.
The next pandemic could be as novel as the virus that causes it.
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