Where be the bugs?

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Cool paper in Nature, Global trends in emerging infectious diseases. Not cool because infectious diseases are great, but I believe they’ve been (and are) major evolutionary pressures on our species. Great map too. From the legend:

a) zoonotic pathogens from wildlife
b) zoonotic pathogens from non-wildlife
c) drug-resistant pathogens
d) vector-borne pathogens

Not surprised about the intersection with world population density. Just by inspection, the Indo-Gangetic plain looks to be the “winner” here! Though it does seem that Sub-Saharan Africa holds its own in terms of representing above its population-weight class in the wild-life derived and vector-born pathogen categories. Might we be able to chalk that up to a long history of coevolution between the African ecosystem and hominid species? Domesticated animals seem to be more of an issue in the old Eurasian Oikumene as you would expect. For more precision on the global trends and correlates, check out their regressions.

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11 Comments

  1. Isn’t it cool how the right edge of maps a and c join with the left edge of maps b and d? I guess the Earth is round!

  2. Not surprised about the intersection with world population density.  
     
    What’s surprising is the resolution. You can actually pinpoint second-tier cities like Lyon and Nizhniy-Novgorod on map A (for some reason, “wildlife-born” pathogens seem concentrated around urban centres). 
     
    it does seem that Sub-Saharan Africa holds its own in terms of representing above its population-weight class in the wild-life derived and vector-born pathogen categories. 
     
    Not when you compare it to other zones at similar latitudes (Meso-America, South / South East Asia). If you factor in population density and economic development, that seems to explain much of the variation in map D.

  3. I knew someone who went hiking in Nepal a lot. He called Kathmandu “the disease capital of the world”. 
     
    Looks like he wasn’t far off.

  4. It would be interesting to find out why there is such a widespread distribution of drug-resistance in India. China and Japan. It might have to do with the fact that either the people themselves are so disease adverse that they over-self-prescribe antibiotics (Japan) or that antibiotics tend to be the only “care” that is given out in poorer areas. I spent a half-hour listening to a ID researcher rant about the danger of antibiotic distribution in the third world once.

  5. Antibiotics have been widely over-prescribed or inappropriately prescribed, patients ‘demand’ them for treatment of colds and flu viruses, then as soon as the symptoms subside they quit taking them. Not so long ago, it was absolutely standard that if you went to a doctor with a dose of flu, he would prescribe an antibiotic as a matter of course, just as a ‘safeguard’ against secondary bacterial infection, and people have been very lax about completing courses of antibiotics. 
     
    Also, it is still not uncommon to be able to get prescription drugs from pharmacies under the counter without a prescription – often the pharmacist may ‘prescribe’ something, or people can just ask for an antibiotic for something. 
     
    The logic tends to be that if you are sick and pay to go to the doctor, he should give you something to fix you, not just tell you to go home and rest and drink lots of fluids. I think there is also probably some cultural confusion here with traditional herbal medicine, whereby when you consult a traditional Chinese medical practitioner, for example, it tends to be in a holistic manner, and he will prescribe some herbal medicine to restore whatever is out of wack – so every time you go, you get some kind of medicine aimed at putting you right, no matter what it is. So going to a western trained doctor, paying and being told there is no medicine and you just have to wait while your body heals itself is not an acceptable outcome. 
     
    The problems with overprescription and inappropriate use of antibiotics are generally better appreciated now, as is the point that an antibacterial drug is not going to do anything to a virus, but it still happens.

  6. Michael – Further, you notice there’s a red spot on the southern coast of China on Map C which coincides with Hong Kong. My guess is that derives from western trained doctors practising in Hong Kong and the easy availability of western medicine like antibiotics, but western medicine not being available in the adjacent southern Chinese hinterland. 
     
    Also, historically Hong Kong has been very bad for tuberculosis because of the extremely high population density, and the only available treatment was antibiotics. 
     
    I think that red spot is the intersection of western medicine, very high population density, and lack of understanding/education about western drugs. Alternatively it could maybe be a data/reporting issue, but I was not surprised to see it.

  7. It might have to do with the fact that either the people themselves are so disease adverse that they over-self-prescribe antibiotics (Japan) or that antibiotics tend to be the only “care” that is given out in poorer areas. 
     
    And yet we hear things like: 
     
    ?????????

  8. Richard, 
     
    translation, please. I’ve taken over two years of Japanese but I’m lazy right now.

  9. Something like “eat something dirty and you won’t get sick.

  10. The intent of the aphorism is something like don’t overprotect your immune system. You have to expose yourself to the environment for your immune system to work.

  11. interesting that the spread of pathogens across the ndo-Gangetic plain is consistent with the argued spread of civilization in “Guns, Germs and Steel”, ie that the ability to travel across such a a wide swath of consistent climate allowed for such rapid cultural and technological advances. the germs are just following our lead, I guess.

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