Geneticist Dr Kat Arney takes a look at the ancient war between our genes and the pathogens that infect us, looking back thousands of years to the Black Death and before, all the way through to our very latest foe.
One of the most curious things about COVID-19 – the disease caused by the novel SARS-CoV-2 coronavirus that’s causing so much trouble – is the wide variation in how it affects different people, from being a very serious or even fatal illness, through a range of strange symptoms like skin rashes or diarrhea as well as the cough, fever and loss of smell, which vary in their severity. And there are some lucky people who seem to catch the virus but have no symptoms at all. So, do these differences lie in our genetics? Or are their other factors at play?
To find out, Kat speaks with consultant geriatrician Dr Claire Steves from King’s College London. She’s part of a team of researchers analysing data from the COVID Symptom Study app, originally built by health science company ZOE to survey some of the thousands of identical and non-identical twins involved in the TwinsUK cohort study. The app now has more than 4 million users in the UK, US and Sweden, and is providing valuable insights into the key symptoms of COVID-19 and how they affect different people.
“We have seen that identical twins are more similar in the symptoms that they’ve had than non-identical twins – that hints at a genetic component to how we experience the disease,” Claire says.
“There may be a difference in terms of heritability or genes that lead to somebody having the infection to the genes that lead to somebody having the infection in a certain way, with certain symptoms. I think that’s going to be key as well – not just looking at the genes which define whether or not the virus has got into your body, but genes that define how your body then reacts to it.”
COVID-19 is just the latest in a long string of outbreaks, epidemics and pandemics that have ravaged humanity over the years. Christiana Scheib, head of the ancient DNA research facility at the University of Tartu, Estonia, is looking at much older plagues – including the Black Death – to discover how underlying genetic variations may have contributed to susceptibility to disease.
By studying ancient remains from many burial sites in the Cambridge area, she’s piecing together a picture of the past to understand how these people lived and died. And, as she’s discovered, they aren’t so different from the population today.
“The thing you learn the most about when you look at the past is that people are just people. A lot of the fears and hardships that people have faced in the past, we still face today. Although I would say that things are much, much better now than they were in the 14th Century – the 14th Century was a dire place!” Christiana says.
“We do find plenty of people living to ripe old ages. Lots of little old ladies living in hospitals and in rural communities. We find lots of children suffering from diseases, malnutrition, which is much less prevalent today. However, genetically the people in Cambridge are actually very similar to the people that live here today who are locals. So as everything changes, a lot also stays the same.”
Finally, Kat talks to Lucy Van Dorp from University College London, who is studying how the human genome has co-evolved over millennia alongside the pathogens that infect us. Although it may seem strange to be studying ancient diseases in today’s modern era, particularly when we’ve got a brand new pandemic to worry about, her work to trace the spread, movement and migration of humans and their pathogens is essential for understanding the spread of outbreaks today, including COVID-19.
“These methods are ones we really should be caring about now, because the spread, movement and migration of humans and their pathogens is something that continues to happen – there are large scale efforts now to reconstruct epidemics and outbreaks using genetic data in conjunction with epidemiological data,” Lucy explains.
“This is allowing us to infer what factors might be important in a hospital outbreak and understand how genomes are either expanding or contracting as we as a society change around them. This is really important, particularly for pathogens, as we have the potential to inform public health interventions and to use genomic surveillance to understand what variants and what parts of the genome we need to be worried about.”
Listen to the full episode and find a full transcript at GeneticsUnzipped.com
Genetics Unzipped is the podcast from the UK Genetics Society, presented by award-winning science communicator Dr Kat Arney and produced by First Create the Media. Follow Kat on Twitter @Kat_Arney, Genetics Unzipped @geneticsunzip, and the Genetics Society at @GenSocUK