My first clue on the existence of specific influenza pandemics before 1918 came a few years ago while reading some local newspapers on the Spanish Flu itself. The papers were warning people that this was not an ordinary flu year, it would be like 1893! The papers referred to 1893 in the same way that we refer to 1918 today. Since then I’ve been intrigued by the 1889-1893 ‘Russian flu’. Yet the Spanish flu of 1918 so dominates publications on influenza pandemics that it has not been easy to find information.
So how do we identify a historic pandemic flu from seasonal flu or a bad cold virus? Morens, Taubenberger, Folkers, and Fauci (2010) have outlined three basic criteria: 1) the standard influenza symptoms (fever, chest congestion, fatigue, body aches, and cough), 2) explosive transmission and directional movement along trade routes, and 3) high morbidity but low mortality. Influenza pandemics kill many people by infecting huge numbers so that a low mortality rate still amounts to many fatalities. Historically the fatalities have been among the very young and very old, pregnant women, and the chronically ill (Morens & Taubenberger, 2010a).
The first recognized pandemic occurred in July and August of 1510 when an outbreak of “gasping oppression” appeared nearly everywhere at once. It was described as a “‘gasping oppression’ with cough, fever, and a sensation of constriction of the heart and lungs”, leaving an impression strong enough for people to write of it decades later (Morens et al, 2010). At least seven contemporary and near-contemporary reports exist of the 1510 pandemic (Morens, North & Taubenberger, 2010). The 1510 outbreak had a high morbidity but low mortality, killing primarily children and those who had been over-bleed (Morens et al, 2010). Francesco Muralto, who lived through the 1510 pandemic, estimated that it killed about ten people in a thousand per day, or about 1% which is comparable to the Spanish flu. Yet, we do have to remember that Muralto was a lawyer and politician not a physician so his estimates of mortality may not be very accurate (Morens, North & Taubenberger, 2010)..
The figure below outlines 15 pandemics in the last 500 years. In this first pandemic and many that followed, influenza occurred during the summer. The frequency of pandemics varies widely from as short as 6 years to 149 years. Not one human pandemic has been recognized in the 17th century, though equine (horse) influenza was identified in 1648. Within the 149 year gap are many local epidemics, some of them quite severe.
These pandemics have gone by many contemporary names. Physician Daniel Sennet (1572-1637) reported that the “names applied to [the 1580 pandemic disease] included febrile catarrh, suffocating fever, epidemic catarrh, coughing epidemic, [and] contagious headache. The Germans called [it] ‘the chirp’, the sheep cough, and the sheep disease, [and] the chicken malady, because sick persons were suffering [as with] the coryza of chickens.” (Morens & Taubenberger, 2010a). Human cases of influenza associated with the great equine influenza panzootic of 1872 were said to have “epizooty” or “zooty”. Le Grippe (the grip) seems to have become a common name for influenza from the time of the Russian flu (1889-1893). Le Grippe is commonly found on death certificates in the early 20th century (at least in my area). For about the last century, pandemics have been known by their reputed city or country of origin: Russian flu (1889-93), Spanish flu (1918), Hong Kong flu (1968-69) and despite great efforts Mexican flu/swine flu (2009). The politics of naming flu pandemics came to the fore like never before in 2009 as neither Mexico or swine producers wanted the flu named after them.
Today we recognize that influenza is primarily evolves in wild birds and then circulates among domestic poultry, humans and swine. Historically influenza was once known primarily as an infection of horses that frequently spread to humans and dogs. Canine infections have frequently been documented, most recently in 2009, but appear to have been historically dead-end hosts. However, there is now an equine influenza H3N8 virus that has adapted to dogs where it its evolving by antigenic drift. Multiple lineages of the now dog virus are spreading internationally (Morens & Taubenberger, 2010a).
Equine influenza (H3N8) has circulated among humans in at least the 19th century. People born before 1893 produced antibody activity against equine influenza decades later. Human susceptibility to equine influenza has also been confirmed experimentally (Morens & Taubenberger, 2010a). Horse epizootics have correlated with influenza-like illness in humans in 1299, 1328, 1404, 1647-48, and 1657-1658. Between 1688 and 1888, Moren and Taubenberger (2010a) counted 112 human epidemics or horse epizootics in Europe. Of these outbreaks, only 20 were human only epidemics, 25 were horse only epizootics, and 67 were horse and human outbreaks. In the Americas over the same 200 year period, influenza-like illness was documented in only 56 years (half that of Europe) with humans and horses in 21 years, humans only 20 years and horses only in 10 years. Morens and Taubenberger (2010a) noted that in all but two years (1776 and 1780) when both horses and humans were infected, equine influenza proceeded the human outbreak by about 3 weeks. Before 1700 it was widely accepted that flu epidemics began with horses and ended with humans. By the mid-19th century it was beginning to be noted that horse outbreaks occurred in four-year cycles, probably due to herd immunity generated by previous epizootics. While human seasonal influenza was a winter phenomenon as it is today, when major human epidemics coincided with horse epizootics the human infections occurred in the spring and summer along with the horse outbreak (Morens & Taubenberger, 2010a).
Host switching between humans and swine has been documented in the twentieth century, most notably in 2009, but Morens and Taubenberger could not find evidence of swine influenza before 1918. Morens and Taubenberger (2010a) suggest that swine have replaced horses as the “secondary extra-human mammalian reservoir”. As swine are susceptible to both avian and human influenza A strains, they are a likely mixing host that could produce an antigenic shift with pandemic potential.
Avian influenza in domestic poultry has garnered a lot of attention for the last decade. Although the few human infections contracted directly from domestic poultry have produced high mortality rates, there is little historical evidence that avian influenza from domestic poultry has directly produced human pandemics even though the pandemic-causing genes ultimately originate in avian influenza from wild birds. The avian epizootic of 1872 that occurred simultaneously with the equine influenza epizootic of 1872 is the best lead for finding an avian influenza capable of causing a mammalian panzootic (Morens & Taubenberger, 2010b).
If influenza has shown us anything over the last 500 years it is that its unpredictable, expect the unexpected. Its host-switching abilities make it likely it will retain the ability to blind side us.
Morens, D., Taubenberger, J., Folkers, G., & Fauci, A. (2010). Pandemic Influenza’s 500th Anniversary Clinical Infectious Diseases DOI: 10.1086/657429.
This article was placed in the public domain and is available for free here.
Morens, D., & Taubenberger, J. (2010a). Historical thoughts on influenza viral ecosystems, or behold a pale horse, dead dogs, failing fowl, and sick swine. Influenza and Other Respiratory Viruses, 4 (6), 327-337 DOI: 10.1111/j.1750-2659.2010.00148.x
Morens DM, & Taubenberger JK (2010b). An avian outbreak associated with panzootic equine influenza in 1872: an early example of highly pathogenic avian influenza? Influenza and other respiratory viruses, 4 (6), 373-7 PMID: 20958931
Morens DM, North M, & Taubenberger JK (2010). Eyewitness accounts of the 1510 influenza pandemic in Europe. Lancet, 376 (9756), 1894-5 PMID: 21155080