Could an 1890 pandemic have been a coronavirus?
Some people have been pointing to a global pandemic in the late 1800s that we used to think was a form of flu, but now some are saying it could actually have been a coronavirus. What’s the story there?
Kyle Harper describes what we can decipher from prior pandemics and their records...
Kyle - It's an interesting question. And, at this point still a kind of speculative hypothesis: but, we know that about a generation before the Spanish flu, there was a global pandemic that people at the time considered influenza. It's actually interesting in a lot of ways, because it's the first global pandemic where you have a really fairly robust global network of instant communication. So the news can travel and people actually can perceive the pandemic in real time as it's happening. So, actually the word pandemic existed before that, but it's actually when the word sort of became a household term.
It was not quite as nasty as the Spanish flu, but it was still a pretty severe disease with a lot of morbidity and mortality. It moved very fast, as a respiratory disease. So the thinking has always been, this it's called the Russian flu, it was believed to have originated somewhere in Russia or central Asia.
The thinking has always been, this was kind of one of these global waves of influenza, which is a reasonable hypothesis. I think still, probably the most likely one, but obviously we're pretty interested in coronaviruses now. There are actually many species of coronavirus. There's four species of coronavirus that are endemic in human populations. They circulate constantly, most of us have probably had a coronavirus or two even before the COVID-19 pandemic, and they cause pretty mild respiratory and the common cold.
The study of one of these coronavirus species, it's called OC43, which is kind of unimaginative, shows that it's most closely related to a bovine coronavirus. So, there was probably in the recent past a common ancestor that infected cows and when it crosses the species barrier, it adapts to humans. It becomes endemic in human populations.
Scientists can use a technique known as molecular clock dating. That's an analysis of how long it would have taken for certain evolutionary changes to accumulate. So, by measuring the genetic differences between human coronavirus OC43 and its close relative bovine coronavirus, it's been estimated that this evolutionary divergence happened around 1890, which means that there should be some new respiratory disease in human populations right around the time there's this big dramatic global pandemic.
So, people have said maybe that wasn't influenza; maybe it was the emergence of this new species of coronavirus as a human disease. I think that's perfectly logical on some evolutionary grounds. But it's still, as far as I know, nobody's been able to prove it. I'll just say that it's the kind of thing that is now potentially provable, genome sequencing technologies are so powerful that it's increasingly possible to recover fragments of pathogen DNA, or even RNA, from past samples, whether from archaeological samples, from skeletal remains or from sometimes aldehyde preserved tissue.
Measles virus has been recovered from the very early 20th Century. I think there's surely someone out there who could find, potentially, lung tissue of somebody who died in the early 1890s and it might be possible to test genetically and really get smoking gun evidence, whether it was influenza or coronavirus.
It's an interesting question to think about. We don't really know. We could potentially, if someone's lucky enough to find a museum specimen, be able to recover the genome of the pathogen, but until then, it'll just sort of remain an interesting speculation. And, it is interesting to think about a possible parallel for the emergence of a new coronavirus and to think about what happens when one of these enters human populations and then unfortunately comes to stay.