8 ms·

Relationship between the ABO Blood Group and the Covid-19 Susceptibility

147 points by car 7y ago

jakozaur 7y ago
Not as dramatic difference as the title suggests... Pulling numbers from the article. 3694 Control (Wuhan area) A: 1188 (32.16%) B: 920 (24.90%) AB: 336 (9.10%) O: 1250 (33.84%) COVID-19 1888 patients A: 715 (37.87%) B: 494 (26.17%) AB: 193 (10.22%) O: 486 (25.74%) The difference may be related to triaging criteria. E.g. different ethnic groups overrepresented in given hospital.
- car 7y ago
  I’d be happy to change the title, though it is basically quoted from the article conclusion. Not peer reviewed, but an interesting observation nevertheless. There will be more data soon.
  - toptal 7y ago
    Given the fact SARS had a similar profile, this should be a reasonable assumption. I’m not saying it’s at the same standard as being peer reviewed, though it’s more likely than not that the conclusions from this data will remain true based on both the data and the correlation.
  - tom_mellior 7y ago
    > I’d be happy to change the title, though it is basically quoted from the article conclusion. For future reference, Hacker News guidelines call for using the article's original title as the title of the submission. https://news.ycombinator.com/newsguidelines.html https://news.ycombinator.com/newsguidelines.html (the moderators seem to have fixed this for you)
- mancerayder 7y ago
  Thanks for posting this. Would others agree here that this is a very weak correlation of blood type to Coronavirus severity?
  - necovek 7y ago
    I would like a hypothesis tested on individual alleles as I outlined in another comment: it's not that weak correlation if looked at that way, especially since eg. A* groups are present in Caucasian population in ~45% compared to ~35% in Asian population (numbers pulled from another site cited in that other comment of mine).
- nicioan 7y ago
  Don’t you have to juxtapose that with the abo % in the population? According to Wikipedia(only showing +, avg, https://en.m.wikipedia.org/wiki/Blood_type_distribution_by_country https://en.m.wikipedia.org/wiki/Blood_type_distribution_by_c...) that’s: O:38.67% A:27.42% B:22.02% AB:5.88% edit: added wikipedia link
  - necovek 7y ago
    They did have a control group from the healthy population of Wuhan which had those at... "ABO group in 3694 normal people in Wuhan showed a distribution of 32.16%, 24.90%, 9.10% and 33.84% for A, B, AB and O, respectively"
david_draco 7y ago
Odds ratios between 0.5 and 1.5 are not exactly considered strong evidence. https://en.wikipedia.org/wiki/Bayes_factor#Interpretation https://en.wikipedia.org/wiki/Bayes_factor#Interpretation
- ced 7y ago
  If you're referring to the odds ratio between group A control and group B covid, then that's not a Bayes factor AFAIK. A Bayes factor is to compare two hypothesis. You can have an odds ratio of 1.00001 which is very significant (eg. female/male birth ratio)
Amorymeltzer 7y ago
Some quick points: - Reported odds ratios[0] of 1.2 for A and 0.67 for O. - This is a preprint, so it has not been peer reviewed. - They compared blood type of patients with that of the general population in the region. - Data is from 2,173 patients at three hospitals. The data varied between them, but Wuhan had the overwhelming majority (1,775, or 81%) of cases. - Since these are all patients, they presumably are weighted toward the more extreme responses. There were minimal age and gender differences, though. - A similar response for type O was apparently reported for SARS. 0: https://en.wikipedia.org/wiki/Odds_ratio https://en.wikipedia.org/wiki/Odds_ratio
- graeme 7y ago
  Did they list an odds ratio for having a severe/critical case?
  - Amorymeltzer 7y ago
    No, they didn't look at severity. They did report ABO distributions for 206 deaths in Wuhan, which could be considered a proxy for severity but likely has a lot of confounding variables, such age, wealth, etc. Those data were in-line with the top-line results, but that's a small sample.
    - usrusr 7y ago
      They are looking at data from hospitals, so I'd expect mild cases to be excluded. Semantic nuances seem to be very relevant to the applicability (or not) of this selection to the exact wording of the result: is a SARS-CoV-2 infection that remains harmless because it is overcome before spreading from throat to lungs classified as a light case of Covid-19 or is that label reserved for more serious forms of infection?
    - gnramires 7y ago
      If ABO type is independent from age/wealth/etc., then those variables don't need to be controlled (although I guess that should indeed be investigated/confirmed first).
mikorym 7y ago
By the way (and not flamebaiting here) this is one of the reasons why "this is natural selection" is the phrase that makes me the most angry in all of this. Death by flu is selection for random shit that cause you to be better off against only one thing and that is: that exact desease causing strain. The worst thing about Covid 19 to me is how it selects against old people, and even worse: Friendly, sociable old people.
- Amorymeltzer 7y ago
  Indeed. Those sort of naturalistic[0] and appeal to nature[1] fallacies are infuriating. One advantage of being human is that "this is how things are" doesn't have to mean "this is how things must be." 0: https://en.wikipedia.org/wiki/Naturalistic_fallacy https://en.wikipedia.org/wiki/Naturalistic_fallacy 1: https://en.wikipedia.org/wiki/Appeal_to_nature https://en.wikipedia.org/wiki/Appeal_to_nature
  - amelius 7y ago
    Sadly, the essence of our economy seems copied from nature with concepts like "winner takes all" and "survival of the fittest".
    - deleted 7y ago
      [deleted]
    - Mirioron 7y ago
      That's because humans need stuff to live. You want an economic system that keeps improving and nature is pretty good at it.
      - TheOtherHobbes 7y ago
        Nature is pretty good at finding good-enough local minima, but (ironically) very poor at finding best-possible intelligent designs. There has never been an economy like the latter, and it's a tragic failure of human imagination to believe that it isn't possible.
Taniwha 7y ago
Because this is the next thing you're going look up: https://en.wikipedia.org/wiki/Blood_type_distribution_by_country https://en.wikipedia.org/wiki/Blood_type_distribution_by_cou...
sub7 7y ago
This has been circulating for a few days now. It's bogus. There is absolutely 0 peer reviewed papers or double blind controlled studies that prove this.
- tappio 7y ago
  Is there some particular reason why this would not pass peer review in some low level journal? Are the statistics off? Or is the data fabricated? Because it will be published and it will pass the peer review if it satisfies those basic conditions. Peer review just means that someone else read the paper and judged whether the content seems reasonable. I don't think it is productive to call an article bogus because it is not peer reviewed. The judgement should be based on content.
- graeme 7y ago
  The original SARS virus had the same relationship and that was peer reviewed. Do you have a basis for saying its bogus? This is a new result. How would you even do a double blind control study. Expose people to the virus?
- ComputerGuru 7y ago
  There are no double blind studies for anything covid just yet.
  - mnw21cam 7y ago
    There might be some slight ethical issues in performing double-blind studies on covid infection susceptibility.
    - ComputerGuru 7y ago
      Right. But there are double blind studies now in progress on the effectiveness of various treatments.
shekharshan 7y ago
I am a little rusty on my probability basics now but I was trying to remember how one would go about answering the following question regarding Wuhan numbers cited in this study: "Given a person has type A blood type, what is the probability of that person having covid19" I remember this being something like P(E1 intersection E2)/P(E2) where E2 = event that a person has type A blood and E1 = event that the person has covid19. In case of Wuhan 32.16% of the population has type A blood. So E2=0.3216. To get E1 we would need total infections/total population for the city. We don't have that number but is this thinking correct?
- vitus 7y ago
  Yes. In particular, as you describe it, you'd then need to solve for P(E1 ∩ E2) by extrapolating from the existing result of P(E2 | E1) present in the article, then plug it into that formula you've provided. (Bayes' law streamlines the whole process by combining the two-step calculation into one.) edit: a slight nitpick: E2 is an event ("this person has type A blood"); P(E2) is a number.
umut 7y ago
This has no more value than being a "fun fact" (sorry for the word 'fun' in the context of a pandemic and death numbers).. a) it is something you don't have any control b) the diff (odds, bayes factor or any similar definition) is not that great to have an effect on public policy (something like, let's focus our resources on region A, since region B has less risk kind of change) So, let's all enjoy this study as food for our curiosity, and move on with all the usual measures of social distancing, extra hygiene control and all.. Especially dangerous, if even one crazy person goes out because he has a certain blood type and helps the disease spread
- ArnoVW 7y ago
  This is how science works. Knowing this may help the production of new theories, that produce new research initiatives, that may result in solutions. Imagine you are debugging a random connection loss issue in prod. You notice that the errors are much more frequent on server-05. Ok, fun fact. So what? What is special about that server? Does it serve customers from a different geographic zone? Is it in another network location?
- crimsonalucard 7y ago
  no, it means type O can do riskier jobs.
  - JoeAltmaier 7y ago
    Because they have 1/3 less chance of death? Not enough difference to convince me (I'm O+)
    - crimsonalucard 7y ago
      Of course not. But when you're knee deep in the situation and it's time to draw straws it's good to know risk tolerance. (I'm O-).
outlace 7y ago
Assuming this result holds... Perhaps anti-A antibodies that may be produced by non-A blood types have some cross-reactivity with the virus?
hirenj 7y ago
I recommend reading the review below on known effects of blood groups on infection. Not super surprising in that blood group may have general effects. I can't think how this would work mechanistically without knowing the glycans on ACE2/TRMPSS2 or the spike, and if they carry antigen (I would expect not). https://www.ncbi.nlm.nih.gov/m/pubmed/26085552 https://www.ncbi.nlm.nih.gov/m/pubmed/26085552
necovek 7y ago
Assuming the equal distribution of homo- and heterozygotes, it looks like the numbers (A/AB +20%, B +3%, 0 -33%) suggest the following: • 00 (homozygote 0, but that's the only way someone is a 0) is at -33% "chance" of catching SARS-Cov-2 • B0 (heterozygote B) is at -10% • BB (homozygote B) is at +5% • AB (well, heterozygote, obviously) is at +20% • A0 (heterozygote A) is at <17% • AA (homozygote A) is at ~33% Basically, the hypothesis would be that presence of an A allele contributes significantly to increased risk (~17%), B is mostly neutral (+1-2%), a 0 allele contributes to decreased risk (-17%). Considering the distribution in healthy individuals (I haven't run the numbers but only used roughly 30% for each group except AB which is at 10% — I've only done the math in my head so I am way more off than that, and it would be quite unlikely for the effect to be so linear as my breakdown above suggests) from the study, everything roughly lines up. It would be interesting if a study could confirm that, but they'd need parents blood types for every individual to be able to get that. I've seen mention of open data sets that include research articles, but is there any data set to look at? It would be quite interesting since the distribution of blood types supposedly differs strongly among "ethnicities" if https://www.livescience.com/36559-common-blood-type-donation.html https://www.livescience.com/36559-common-blood-type-donation... is to be trusted — their "Asian" number for AB is also at 7% compared to 9% in their "health population" number. If there was data just documenting whatever findings there are for patients, it would help in independent "researchers" find correlations that might not be obvious to others.
mrfusion 7y ago
How can blood type matter? What’s the mechanism of action?
- bluGill 7y ago
  Who knows. Maybe this is a fluke maybe not. When you notice a correlation you study it. Sometimes you discover it isn't significant and stop further study. Sometimes it is significant so you study more. That isn't to say your question is bad, just that it could be years before we understand.
- tathougies 7y ago
  I mean blood type is literally molecules exposed on the outside of blood cells. I believe they are exposed on other cells, not just on blood cells. Viruses bind to receptors on the cell wall in order to infiltrate the cell. Perhaps the A blood type receptor makes it easier for the virus to enter?
- hirenj 7y ago
  Excellent question! Here's the answer: We have no idea! Blood type antigens are complex carbohydrates, and A/B/O is the difference between N-acetyl-Galactosamine/Galactose/nothing at the end of a sugar chain. So let's talk about Coronavirus and sugars. SARS-COV-2 (and the prequel for that matter) are relatively unique for viruses because they don't (as far as we know) use sugars (sialic acids to be specific) to bind to cells, unlike all of our other favourite viruses (e.g. influenza). BUT that's not the only place it could matter. Maybe sugars help organise the membrane to increase multivalent reactions, and there's some galectin that binds to B antigen. Or the virus itself somehow carries the antigen, and A/B protects against furin processing? Lots of possibilities. First thing I would check for is co-expression of ABO with ACE2. If it's not in the same cells, then I have NO idea how it works.
Vysero 7y ago
Well.. I don't know what blood type I am but it is somehow comforting to know that there are at least some people out there who have a better chance at not getting sick.
sdiq 7y ago
Slight nitpick: I find the use of 'normal people' in the article a bit distracting. I appreciate the fact that the authors are not native English speakers but using 'the general population' was more appropriate here. However, being a blood type 'O', I am not sure whether this consoles me.

147 points by car 7y ago

Not as dramatic difference as the title suggests... Pulling numbers from the article. 3694 Control (Wuhan area) A: 1188 (32.16%) B: 920 (24.90%) AB: 336 (9.10%) O: 1250 (33.84%) COVID-19 1888 patients A: 715 (37.87%) B: 494 (26.17%) AB: 193 (10.22%) O: 486 (25.74%) The difference may be related to triaging criteria. E.g. different ethnic groups overrepresented in given hospital.

car 7y ago
I’d be happy to change the title, though it is basically quoted from the article conclusion. Not peer reviewed, but an interesting observation nevertheless. There will be more data soon.
- toptal 7y ago
  Given the fact SARS had a similar profile, this should be a reasonable assumption. I’m not saying it’s at the same standard as being peer reviewed, though it’s more likely than not that the conclusions from this data will remain true based on both the data and the correlation.
- tom_mellior 7y ago
  > I’d be happy to change the title, though it is basically quoted from the article conclusion. For future reference, Hacker News guidelines call for using the article's original title as the title of the submission. https://news.ycombinator.com/newsguidelines.html https://news.ycombinator.com/newsguidelines.html (the moderators seem to have fixed this for you)
mancerayder 7y ago
Thanks for posting this. Would others agree here that this is a very weak correlation of blood type to Coronavirus severity?
- necovek 7y ago
  I would like a hypothesis tested on individual alleles as I outlined in another comment: it's not that weak correlation if looked at that way, especially since eg. A* groups are present in Caucasian population in ~45% compared to ~35% in Asian population (numbers pulled from another site cited in that other comment of mine).
nicioan 7y ago
Don’t you have to juxtapose that with the abo % in the population? According to Wikipedia(only showing +, avg, https://en.m.wikipedia.org/wiki/Blood_type_distribution_by_country https://en.m.wikipedia.org/wiki/Blood_type_distribution_by_c...) that’s: O:38.67% A:27.42% B:22.02% AB:5.88% edit: added wikipedia link
- necovek 7y ago
  They did have a control group from the healthy population of Wuhan which had those at... "ABO group in 3694 normal people in Wuhan showed a distribution of 32.16%, 24.90%, 9.10% and 33.84% for A, B, AB and O, respectively"

david_draco 7y ago

Odds ratios between 0.5 and 1.5 are not exactly considered strong evidence. https://en.wikipedia.org/wiki/Bayes_factor#Interpretation https://en.wikipedia.org/wiki/Bayes_factor#Interpretation

ced 7y ago
If you're referring to the odds ratio between group A control and group B covid, then that's not a Bayes factor AFAIK. A Bayes factor is to compare two hypothesis. You can have an odds ratio of 1.00001 which is very significant (eg. female/male birth ratio)

Amorymeltzer 7y ago

Some quick points: - Reported odds ratios[0] of 1.2 for A and 0.67 for O. - This is a preprint, so it has not been peer reviewed. - They compared blood type of patients with that of the general population in the region. - Data is from 2,173 patients at three hospitals. The data varied between them, but Wuhan had the overwhelming majority (1,775, or 81%) of cases. - Since these are all patients, they presumably are weighted toward the more extreme responses. There were minimal age and gender differences, though. - A similar response for type O was apparently reported for SARS. 0: https://en.wikipedia.org/wiki/Odds_ratio https://en.wikipedia.org/wiki/Odds_ratio

graeme 7y ago
Did they list an odds ratio for having a severe/critical case?
- Amorymeltzer 7y ago
  No, they didn't look at severity. They did report ABO distributions for 206 deaths in Wuhan, which could be considered a proxy for severity but likely has a lot of confounding variables, such age, wealth, etc. Those data were in-line with the top-line results, but that's a small sample.
  - usrusr 7y ago
    They are looking at data from hospitals, so I'd expect mild cases to be excluded. Semantic nuances seem to be very relevant to the applicability (or not) of this selection to the exact wording of the result: is a SARS-CoV-2 infection that remains harmless because it is overcome before spreading from throat to lungs classified as a light case of Covid-19 or is that label reserved for more serious forms of infection?
  - gnramires 7y ago
    If ABO type is independent from age/wealth/etc., then those variables don't need to be controlled (although I guess that should indeed be investigated/confirmed first).

mikorym 7y ago

By the way (and not flamebaiting here) this is one of the reasons why "this is natural selection" is the phrase that makes me the most angry in all of this. Death by flu is selection for random shit that cause you to be better off against only one thing and that is: that exact desease causing strain. The worst thing about Covid 19 to me is how it selects against old people, and even worse: Friendly, sociable old people.

Amorymeltzer 7y ago
Indeed. Those sort of naturalistic[0] and appeal to nature[1] fallacies are infuriating. One advantage of being human is that "this is how things are" doesn't have to mean "this is how things must be." 0: https://en.wikipedia.org/wiki/Naturalistic_fallacy https://en.wikipedia.org/wiki/Naturalistic_fallacy 1: https://en.wikipedia.org/wiki/Appeal_to_nature https://en.wikipedia.org/wiki/Appeal_to_nature
- amelius 7y ago
  Sadly, the essence of our economy seems copied from nature with concepts like "winner takes all" and "survival of the fittest".
  - deleted 7y ago
    [deleted]
  - Mirioron 7y ago
    That's because humans need stuff to live. You want an economic system that keeps improving and nature is pretty good at it.
    - TheOtherHobbes 7y ago
      Nature is pretty good at finding good-enough local minima, but (ironically) very poor at finding best-possible intelligent designs. There has never been an economy like the latter, and it's a tragic failure of human imagination to believe that it isn't possible.

Taniwha 7y ago

Because this is the next thing you're going look up: https://en.wikipedia.org/wiki/Blood_type_distribution_by_country https://en.wikipedia.org/wiki/Blood_type_distribution_by_cou...

sub7 7y ago

This has been circulating for a few days now. It's bogus. There is absolutely 0 peer reviewed papers or double blind controlled studies that prove this.

tappio 7y ago
Is there some particular reason why this would not pass peer review in some low level journal? Are the statistics off? Or is the data fabricated? Because it will be published and it will pass the peer review if it satisfies those basic conditions. Peer review just means that someone else read the paper and judged whether the content seems reasonable. I don't think it is productive to call an article bogus because it is not peer reviewed. The judgement should be based on content.
graeme 7y ago
The original SARS virus had the same relationship and that was peer reviewed. Do you have a basis for saying its bogus? This is a new result. How would you even do a double blind control study. Expose people to the virus?
ComputerGuru 7y ago
There are no double blind studies for anything covid just yet.
- mnw21cam 7y ago
  There might be some slight ethical issues in performing double-blind studies on covid infection susceptibility.
  - ComputerGuru 7y ago
    Right. But there are double blind studies now in progress on the effectiveness of various treatments.

shekharshan 7y ago

I am a little rusty on my probability basics now but I was trying to remember how one would go about answering the following question regarding Wuhan numbers cited in this study: "Given a person has type A blood type, what is the probability of that person having covid19" I remember this being something like P(E1 intersection E2)/P(E2) where E2 = event that a person has type A blood and E1 = event that the person has covid19. In case of Wuhan 32.16% of the population has type A blood. So E2=0.3216. To get E1 we would need total infections/total population for the city. We don't have that number but is this thinking correct?

vitus 7y ago
Yes. In particular, as you describe it, you'd then need to solve for P(E1 ∩ E2) by extrapolating from the existing result of P(E2 | E1) present in the article, then plug it into that formula you've provided. (Bayes' law streamlines the whole process by combining the two-step calculation into one.) edit: a slight nitpick: E2 is an event ("this person has type A blood"); P(E2) is a number.

umut 7y ago

This has no more value than being a "fun fact" (sorry for the word 'fun' in the context of a pandemic and death numbers).. a) it is something you don't have any control b) the diff (odds, bayes factor or any similar definition) is not that great to have an effect on public policy (something like, let's focus our resources on region A, since region B has less risk kind of change) So, let's all enjoy this study as food for our curiosity, and move on with all the usual measures of social distancing, extra hygiene control and all.. Especially dangerous, if even one crazy person goes out because he has a certain blood type and helps the disease spread

ArnoVW 7y ago
This is how science works. Knowing this may help the production of new theories, that produce new research initiatives, that may result in solutions. Imagine you are debugging a random connection loss issue in prod. You notice that the errors are much more frequent on server-05. Ok, fun fact. So what? What is special about that server? Does it serve customers from a different geographic zone? Is it in another network location?
crimsonalucard 7y ago
no, it means type O can do riskier jobs.
- JoeAltmaier 7y ago
  Because they have 1/3 less chance of death? Not enough difference to convince me (I'm O+)
  - crimsonalucard 7y ago
    Of course not. But when you're knee deep in the situation and it's time to draw straws it's good to know risk tolerance. (I'm O-).

outlace 7y ago

Assuming this result holds... Perhaps anti-A antibodies that may be produced by non-A blood types have some cross-reactivity with the virus?

hirenj 7y ago

I recommend reading the review below on known effects of blood groups on infection. Not super surprising in that blood group may have general effects. I can't think how this would work mechanistically without knowing the glycans on ACE2/TRMPSS2 or the spike, and if they carry antigen (I would expect not). https://www.ncbi.nlm.nih.gov/m/pubmed/26085552 https://www.ncbi.nlm.nih.gov/m/pubmed/26085552

necovek 7y ago

Assuming the equal distribution of homo- and heterozygotes, it looks like the numbers (A/AB +20%, B +3%, 0 -33%) suggest the following: • 00 (homozygote 0, but that's the only way someone is a 0) is at -33% "chance" of catching SARS-Cov-2 • B0 (heterozygote B) is at -10% • BB (homozygote B) is at +5% • AB (well, heterozygote, obviously) is at +20% • A0 (heterozygote A) is at <17% • AA (homozygote A) is at ~33% Basically, the hypothesis would be that presence of an A allele contributes significantly to increased risk (~17%), B is mostly neutral (+1-2%), a 0 allele contributes to decreased risk (-17%). Considering the distribution in healthy individuals (I haven't run the numbers but only used roughly 30% for each group except AB which is at 10% — I've only done the math in my head so I am way more off than that, and it would be quite unlikely for the effect to be so linear as my breakdown above suggests) from the study, everything roughly lines up. It would be interesting if a study could confirm that, but they'd need parents blood types for every individual to be able to get that. I've seen mention of open data sets that include research articles, but is there any data set to look at? It would be quite interesting since the distribution of blood types supposedly differs strongly among "ethnicities" if https://www.livescience.com/36559-common-blood-type-donation.html https://www.livescience.com/36559-common-blood-type-donation... is to be trusted — their "Asian" number for AB is also at 7% compared to 9% in their "health population" number. If there was data just documenting whatever findings there are for patients, it would help in independent "researchers" find correlations that might not be obvious to others.

mrfusion 7y ago

How can blood type matter? What’s the mechanism of action?

bluGill 7y ago
Who knows. Maybe this is a fluke maybe not. When you notice a correlation you study it. Sometimes you discover it isn't significant and stop further study. Sometimes it is significant so you study more. That isn't to say your question is bad, just that it could be years before we understand.
tathougies 7y ago
I mean blood type is literally molecules exposed on the outside of blood cells. I believe they are exposed on other cells, not just on blood cells. Viruses bind to receptors on the cell wall in order to infiltrate the cell. Perhaps the A blood type receptor makes it easier for the virus to enter?
hirenj 7y ago
Excellent question! Here's the answer: We have no idea! Blood type antigens are complex carbohydrates, and A/B/O is the difference between N-acetyl-Galactosamine/Galactose/nothing at the end of a sugar chain. So let's talk about Coronavirus and sugars. SARS-COV-2 (and the prequel for that matter) are relatively unique for viruses because they don't (as far as we know) use sugars (sialic acids to be specific) to bind to cells, unlike all of our other favourite viruses (e.g. influenza). BUT that's not the only place it could matter. Maybe sugars help organise the membrane to increase multivalent reactions, and there's some galectin that binds to B antigen. Or the virus itself somehow carries the antigen, and A/B protects against furin processing? Lots of possibilities. First thing I would check for is co-expression of ABO with ACE2. If it's not in the same cells, then I have NO idea how it works.

Vysero 7y ago

Well.. I don't know what blood type I am but it is somehow comforting to know that there are at least some people out there who have a better chance at not getting sick.

sdiq 7y ago

Slight nitpick: I find the use of 'normal people' in the article a bit distracting. I appreciate the fact that the authors are not native English speakers but using 'the general population' was more appropriate here. However, being a blood type 'O', I am not sure whether this consoles me.