Full text of virologist Dr Kirsty Short’s talk: How Did The 1918 Flu Pandemic Start And Could We Have Another One?
Dr Kirsty Short – Virologist, University of Queensland
So, this year is 2018, and it is a pretty significant year because it marks the anniversary of many important events in our history.
So, it has actually been 20 years since the release of possibly the greatest musical hit of all time, The Backstreet Boys: The Backstreet is Back. Okay, personal preference in music.
But it is also an anniversary of much more significant world events, things like it has been 50 years since the assassination of Dr. Martin Luther king. It has been 100 years this year since the end of World War I and it has been a hundred years since the 1918 Spanish flu pandemic.
So, this 1918 Spanish flu pandemic, the mortality estimates vary but it is largely accepted that it killed 50 million people worldwide. This virus killed more people in 24 weeks than HIV killed in 24 years.
Okay, this has been described as the greatest medical holocaust in history and I think it is really hard for us in this day and age to appreciate how severe this was.
But I want you to imagine that the death toll was so severe that in some countries, they actually ran out of coffins.
So, what was it about this 1918 virus that made it so bad?
I mean, every year we have outbreaks of flu, and 2017 was a bad year for the flu, we know that but it was nothing like 1918.
So, what is the difference between a seasonal flu strain and a pandemic flu strain?
Well, a flu pandemic typically happens when a new flu virus enters the human population, we do not have much pre-existing immunity to it and it is easily transmissible from person to person.
Now, we still do not know really where the 1918 virus came from. What we do know is that originally all flu strains actually come from wild birds. From here, they can actually transmit to other bird species like poultry and they can also transmit to mammals like horses, pigs and of course, humans.
For these animal viruses to jump in the human population, there is kind of really two ways that it can happen. So, firstly it can be a direct infection, so we can get infected with bird flu and you have probably heard that in the news. But it can also be a bit more of a gradual process whereby a virus spreads from a bird to say, a pig, it then becomes much more adapted to the mammalian system and then it crosses over to us.
In the case of 1918, we think what happened is that the virus actually directly jumped into the human population from birds but it is pretty hard to know definitively. And the reason is because in 1918, we did not have the advanced molecular genetics techniques that we have today.
In fact, flu virus itself was not even discovered until the 1930s, so imagine how scary it would have been in 1918 where you saw all these people dying but you did not even know what a flu virus was.
There were still some people who actually still believed in the idea of miasma and that infectious disease was actually just caused by bad air.
So, now let us jump forward, go through history a little bit and fast forward to 2009, and the 2009 swine flu pandemic.
Now, I am sure most of you remember that. If you were lucky like me, you got the swine flu virus and it was pretty nasty, I can tell you from personal experience. So, this virus first emerged at the start of 2009 and it spread rapidly around the world. So, within the first year it infected between say, 10% and 20% of the world’s population. This virus was actually a combination between human, pig and bird flu strains and they kind of came together, so that is why calling this swine flu is a little bit of a misnomer because the virus is much more promiscuous in its origins than just swine flu.
And yes, viruses can be promiscuous, it is about as fun as we get as serologists, so go with it.
So, 2009, it was a pandemic but it was not nearly as severe as 1918. The pandemic killed probably about 300,000 people worldwide but what this pandemic served to emphasize is that once again, we have a pandemic because a virus has jumped from the animal population into the human population and the problem that we have is this phenomena is not just restricted to flu, okay?
This jumps between viruses of different species, happens throughout history. So, to illustrate this point, I want you to cast your minds back to sort of 2002-2003. Now, these were much simpler times. Donald Trump was busy running a reality TV show and not the United States of America, maybe doing one more successfully than the other, you can judge.
We had the amazing technology of those old Nokia phones, if you remember those. I remember being blown away and thinking that nothing could ever get better than this old Nokia phone, but actually at the start of 2003, I was traveling back to Australia, going by Singapore and I remember that Singapore airport was in absolute chaos, okay? They had temperature checks, which everyone had to walk through. It would check if you had 37 degrees or higher.
People were wearing face masks, everyone was a bit panicked and the reason was it was because of the outbreak of this new virus called ‘SARS’ or ‘Severe Acute Respiratory Syndrome’. Now, SARS virus first emerged in China and it rapidly spread to around 30 countries across the world.
Now, the case fatality rate of size probably was not that bad around nine percent but it had a massive economic impact. It cost the world economy about 50 billion dollars. Now, this was not just in terms of increased medical expenses but it was also the productivity losses associated with closed schools closed businesses and a dramatic drop in tourism.
So, at the peak of the size outbreak, there was something like a 70% drop in international travel and about a 60% drop in hotel occupancy rates. Now, very early in the SARS outbreak, there were certain clues that this virus had jumped into the human population from animal species and this is because some of the early SARS patients were living very closely to a variety of different animals or they were frequenting things like live poultry markets. So, all these kind of epidemiological indicators that maybe the virus could have come from animals.
And actually what researchers did is they went through and they did a lot of sampling of weird and wonderful critics and what they found is actually a virus that looked exactly like the human SARS virus in civic cats located at some of these markets.
Now, for those of you who do not know what a civic cat looks like, it looks sort of like a possum with spots, I guess. Apologies to the civic cat enthusiasts out there, five little the civic cat but this is kind of the image of the creature you should have in your mind. Now, it did not really seem to fit with all the evidence to say that these animals were the original source of the SARS virus and the reason was is that, although these civic cats were positive for the virus in these live poultry markets, wild civic cats were not positive for the virus. So, it did not seem like the virus was endemic as such to the civic cat population.
So, what actually was discovered subsequently is that the virus was harbored by a small Chinese bat called a ‘Chinese horseshoe bat’ and what was thought to happen was that this bat was the original reservoir of the virus and once again the sequence of the virus matched that in civic cats and in humans and it actually transmitted the virus to the human population by an intermediate host, which in this case was most likely to be the poor civic cat.