A ‘gotchya’ question posed frequently by talking heads in the media through this covid pandemic has been “but what about all the asymptomatic cases?” As though this proved we were panicking over nothing.
Ready to toil with the reality of asymptomatic Ebola? I got you fam.
Today’s Moment of Science… the incredibly common occurrence of asymptomatic disease.
Give or take, 40% of SARS-CoV2 infections present subclinically, which is also known as an asymptomatic infection. Your odds of lucking out with an asymptomatic case get worse with advanced age and compounding health issues. Some combination of health, genetic plinko chips and dumb luck differentiates between who gets what. It’s a bit of a crapshoot.
However, the whole discussion of asymptomatic cases is a distraction from the real problem at hand: there are an assload of ‘highly symptomatic, possibly gonna fuck up your health for a while’ cases that we need to take care of. Even with a fatality rate that isn’t zombie apocalypse level, over half a million Americans have died in about a year, a number that no flu epidemic has come close to since 1918.
This disease will likely kill more Americans by this summer than AIDS has killed in four decades.
‘But SciBabe,’ I pretend you’re interjecting, ‘Isn’t the high number of asymptomatic cases unique about this disease? Isn’t this incredibly unusual?’
It’s not, and I’m tired of pretending it is.
Allow me to introduce you to the following diseases you may not have been aware likewise can present with asymptomatic cases.
The most common of common colds, i.e. rhinoviruses. One study from McMaster University found 60% of infections on campus to be asymptomatic.
The flu. Estimates vary but range from 20-50% of flu cases having no symptoms, and a robust study in the Lancet suggests that most cases of the flu are asymptomatic. In a typical year, the flu kills about a half a million people worldwide, so maybe it’s wiser to focus the people who are suffering than the asymptomatic cases.
What about other coronaviruses? The endemic coronaviruses that cause “just a cold” can also cause just a nothing. They can be asymptomatic.
SARS- as in the first one- had documented asymptomatic cases. It’s likely we don’t have a full account of asymptomatic spread of the disease, but in a small study of hospital workers, about 10% of people who developed antibodies had no symptoms.
MERS- as in Covid’s and SARS’ big tough older cousin on steroids who’s ready to fuck up absolutely everything in its wake? About 25% of cases overall are suspected to be asymptomatic, and it’s 40-80% asymptomatic for children. (But it kills like 25% of people, so… maybe don’t hyperfocus on the asymptomatic cases and rush to open schools in a MERS pandemic).
How about some ‘keep you the fuck up at night’ scary diseases?
Hepatitis C- Thirty percent of hepatitis C infections are asymptomatic and clear themselves in six months. Your liver and your junk are young and healthy, who needs condoms?
Asymptomatic Ebola? Yeah. That’s a thing too. With a wide range of estimates for the percentage of asymptomatic infections, stick a pin at about 20% of cases showing no symptoms. Spin that wheel on a one in five chance of asymptomatic hemorrhagic fever!
To really get this into perspective, let’s talk polio (and some asymptomatic polio still spreads, in case you hadn’t lost enough sleep in the last year). Estimates are that polio cases are between 75% and 95% asymptomatic. Only 1% of polio infections have paralytic effects (including everything from partial paralysis to the iron lung), and a very small fraction of paralytic cases results in fatalities.
Covid is much deadlier than polio. It also leaves a much higher percentage of people who get infected with long term health problems. I think about that a lot.
Right now, you could have a bunch of asymptomatic shit floating around your body. Dormant cases of herpes and chicken pox, maybe an asymptomatic cold virus or three. And who knows, you might even have syphilis. That’s asymptomatic… until it isn’t.
But what you don’t have is any assurance that you’ll come out the other side of COVID19 unscathed. Small studies have shown that around half of subclinical cases present with heart and/or lung damage. It’s an illness that kills approximately 1% of people and likely leaves 10-15% of patients suffering with long term health problems, and that’s what we should have been talking about all along.
This has been your daily Moment of Science reminding Texans that they’re still free to wear masks.
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Citations and whatnot:
McMaster cold study: https://www.sciencedaily.com/rel…/2012/06/120619225719.htm
Lancet flu study: https://www.thelancet.com/…/PIIS2213-2600(14…/fulltext
SARS, p28: https://www.who.int/csr/sars/en/WHOconsensus.pdf?ua=1https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3371799/
MERS: https://pubmed.ncbi.nlm.nih.gov/30550839/
Hepatitis: https://www.who.int/news-room/fact-sheets/detail/hepatitis-c
Other coronaviruses with incidents of asymptomatic cases: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3805243/
Asymptomatic spread of polio: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4663665/
Asymptomatic covid cases with lung damage: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7462877/
My nightmare is something like nCoV-2, aka COVID-19, with an infectious dose around the frightfully low number of viral particles required to become infected as norovirus does. Around 6 – 8 viruses and you’re stuck close to the toilet for a few days, worse if you’re elderly or have comorbidities.
Ebola, I’m not especially concerned with (as in performing patient care of an infected patient), the infectious dose is rather high and properly followed universal precautions are highly effective.