How’s that for a title? It’s literally got it all.
I LOVE a conspiracy theory. Just when I despair at humanity’s thundering lack of imagination, someone joins the dots in a completely new way, and reveals a picture that doesn’t look like a cat at all. It’s like watching the X-Files in real time.
Epidemiology is also about joining the dots in creative ways. And, if you’re not into felting, it’s a serviceable hobby for the middle aged, ‘creative’ thinker. Nowadays, of course, everyone is an armchair epidemiologist, but only when it comes to COVID19. I’ve yet to notice the Twitter shut-ins hold forth on diabetes. YAWN.
Back to conspiracy theories. Have a look at this town.
Pretty, isn’t it? This is Thurso, in the Thurso-Dounreay region of northern Scotland. It’s a lovely wee spot with good surfing, if you can eat enough shortbread to maintain a thick enough layer of insulation.
Here’s another picture:
This is Dounreay, just along the coast. Dounreay is The Capital of Scottish Ping-Pong.
OK, it’s not. That big round thing is a nuclear reactor.
In the late 1970s and early 80s, Dounreay-Thurso’s children started getting sick. More specifically, the region surrounding the power plant had a statistically significant increase in cases of childhood leukaemia;
Observed numbers of cases of leukaemia and non-Hodgkin’s lymphoma and observed to expected ratios with expected numbers based on Scottish national rates were determined. In 1968-91, 12 cases were observed compared with 5.2 expected in the zone < 25 km from the Dounreay plant (p = 0.007). In the latest period, 1985-91, which has not previously been examined, four cases were observed compared with 1.4 expected (p = 0.059). (from here)
Now, if you’re living in the shadow of a nuclear reactor and children start getting sick with leukaemia, it doesn’t take long to cast an eye towards Giant Ping Pong Ball of Doom. Which is, of course, exactly what everyone did.
I’m not going to get into the definition of clusters because that would be exceedingly dull and require another cardigan, but the short version is, you work out an average number of cases per kilometre (or some other metric) and then see if your cluster exceeds what’s expected. And Dounreay did.
Radiation is a bit of a bugger. So much so, that humans have been looking into it for quite some time. In the case of Dounreay, scientists measured the amount of radiation and unequivocally found that it was too low to be causing the cluster of disease. What they did notice, however, was that the region had experienced an influx of workers, which lead them to suspect another culprit;
Population mixing simply describes the effect of one population with a more robust immunity mixing with another with a more naive immunity. It describes the process where anything from polio to influenza to measles wreaks havoc on a naive community.
Infectious diseases are a dead-set bummer, as 2020 has reminded us with startling alacrity. Suddenly we’re all feeling a bit less Sex in the City and a bit more Inca.
As we’re all very aware, death is the infectious disease’s primary side effect, but there are other effects too.
It’s long been known that infectious diseases can cause other illnesses, long after the initial illness has passed, like rheumatic fever (which I have personally had the pleasure of experiencing) or the flu and its (still controversial) role in the development of adult onset schizophrenia.
Indeed, everything from diabetes to leukaemia gets the glad-eye from the infectious disease weirdos.
In Dounreay-Thurso, epidemiologists suspected that workers from outside the region were bringing novel infections with them, infections to which the children had little background immunity. It’s long been suspected that infectious disease has a role to play in childhood leukaemia. In 2018 British scientist Professor Mel Greaves released a hypothesis that argued that childhood ALL (the most common type of leukaemia) was likely caused by a combination of genetic predisposition and the timing of novel infections. It looks pretty promising, but then what would I know?
The idea is partly based on the ‘hygiene hypothesis’ – children aren’t exposed to the right kind of viruses and bacteria at the right times.
Which brings me to COVID19. Is COVID19 novel enough for our children’s immune systems to recognise it as a novel pathogen, thus causing an increase in childhood leukaemias in the near future? Or is it close enough to other coronaviruses that children already have some extant immunity?
I’m pretty sure the children of Dounreay-Thurso had some immunity to the kinds of infections that were being introduced into their communities. I mean, northern Scotland is remote, but it’s not Mars.
Conversely, as children are sequestered at home and sanitised like a Woolies chook every time they step outside the door, will this result in an increase of leukaemia, as young children fail to acquire exposure to every day viruses and bacterias? Obviously, in some countries, self-isolation is strongly delineated by class. Will this show up in the years to come?
Will we see a rise in childhood leukaemia as a result of widespread infection with COVID19?
Or, will we see a rise in childhood leukaemia as a result of the precautions we’ve taken against COVID19?
Or is childhood leukaemia simply too rare for these effects to form a signal above the noise?
This is the kind of thing I wonder when I’m lying in bed at night. It may also be why I don’t get invited out to dinner very often.