Monday 27 April 2020

Epidemiology is Hard

Here we go again!

-No, there is no evidence of 30 strains, or 8 strains or even 2 strains of SARS-CoV2. There is currently 1 strain and the genome of the virus seems pretty stable. If you heard information about MANY strains it is either bulls*** or somebody is talking about phylogenetic ‘strains’ (in fact they shouldn’t really use term strain in my opinion, but many people does which makes it a bit more confusing for non-scientists) so changes in the viral genome which can help us track spread around the world and create something like viral ‘family tree’. All of those changes are very small and does not change function of any of the viral proteins.
- When I say ‘no evidence’ means there is no evidence YET, but that can change when we will get new data or information. Or might not change at all. When WHO says there is ‘no evidence’ that COVID infection gives you immunity for recurring infections it means that we don’t have that data yet, so we cannot say if this immunity exists or not. It is very early and that is a new pathogen. We cannot tell if the immunity exists and how long it lasts cause not enough time has passed for us to perform tests and get this data. But the data and research so far looks promising, it seems that most of the people develop some level of immunity. How long it lasts? It is hard to say, but hopefully, at least several months as with SARS-1. I know that many of you read scary stories from Asian countries that people are getting re-infected after being discharged from the hospitals but:

*it is only very small number of all the people who got discharged from the hospital

*there is a chance that some of those second positives are false positives. There is no test, which would be 100% false proof, and there are human errors as well.

*there is a big chance that test picks up fragments of ‘dead’ virions, which just did not get cleared out by immune cells yet. Many of those tests were followed by tries to culture those virions in laboratory, and they could not get ‘live’ viruses from it so it seems that what was there was already dead.

*it might have been just first infection which just did not get fully cleared out and reappeared after some time, BUT most (if not all) of those cases has either no symptoms or very mild symptoms after second positive test. Most of the studies say that people with second positive test probably are unable to infect others.

Also having antibodies doesn’t mean you are not immune. I know. Confusing, but immunology is a b****. I’m saying that as person who tortured herself by doing entire course in immunology during my MSc degree, and now is writing DPhil partially in immunology. Don’t do that to yourself. I think immunology is one of the most confusing biological fields out there. Seriously, having antibodies, not having antibodies, having one type of antibodies but no other types of antibodies does not tell us if we have immunity to the pathogen or not 

. There are also B cells, T cells, CD4/CD8, TLRs, and million of other super weird things which makes me cry at night.

- There were some reports about COVID-19 causing blood clots in healthy young adults in US. I just wanted to say that morbidly obese is not healthy. I would also argue that obese is not healthy and yes, being obese makes you more prone to develop severe symptoms of COVID. That’s also because of immunological stuff - inflammation and fat tissue are quite related. Strokes and obesity are also related.

-And just one more thing, comparing countries and measures they used to battle pandemics really does not make sense especially when bringing extreme examples. Like for example - Hong Kong. No, they did not ‘won’ with COVID because they all use masks. They are very small country, which makes it easier to control. They have previous experiences in fighting similar epidemics (SARS-1). And last but not least, people in Hong Kong know how to use masks. And yes, you are more prone to get infections if you are using masks wrong. They are not silver bullet. There is no silver bullet.

- If you feel ill, got cough, fever etc. It is still very possible you have seasonal flu or flu-like illness. It doesn’t mean it is COVID. It does mean though you should stay at home.

 Speaking as a Rocket Scientist... medicine is hard. General Practice requires a degree of intuition and observation that would make Sherlock Holmes proud. Immunology,  the study of immune systems - extremely complex systems - where our tools for investigating them are so crude  - is like trying to analyse a large scale integrated circuit using a jewellers loupe and flint axe.

1 comment:

Chris Phoenix said...

Have you found enough numbers to answer this question? I haven't - I keep seeing obesity listed as a risk factor. But the proportion of COVID deaths with obesity isn't that much higher than the proportion of the population with obesity. And obesity is highly correlated with type 2 diabetes, which is definitely a risk factor.

So if someone is obese and not diabetic, how much extra risk do they actually have?