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| “A terrified man realizing he has just contracted the plague, surrounded by a group of people.” By E.M. Ward, 1848. |
Even the most lethal pathogens we know of don’t kill every single infected individual.1. Sometimes this is because the pathogen that infects the person is relatively weak. Sometimes it’s because the dose was low. And sometimes it’s because of something intrinsic to the patient. Some people are genetically resistant to HIV, because they have a mutated receptor, for example.
The opposite is also true. Sometimes people are more intrinsically susceptible to a pathogen. That became terribly clear during the AIDS epidemic, when quite innocuous agents started killing people, but there are probably many, many natural genetic variants that make us susceptible to some pathogens, just as some make us resistant. When epidemiologists look for “risk factors” that increase mortality or disease severity, this is part of the information they’re trying to tease out, in a rather crude way Sorting this out is part of the goal of the whole personalized medicine movement.
A fascinating example was just documented in MMWR. 2 Here a researcher was working with a genetically modified form of Black Plague bacteria (Yersinia pestis). This bacteria should have been harmless, because it had had its ability to grab iron from the host removed. 3. But the researcher became infected, and died, of an infection with the weakened strain.
We now learn that this was probably because the researcher had his own genetic mutation, hereditary hematochromatosis, which leads to increased levels of iron in the blood. He may4 have been uniquely susceptible to this strain,5 which could only infect people who conveniently made extra iron available to it:
Conceivably, hemochromatosis-induced iron overload might have a similar effect, enhancing the virulence of the infecting KIM D27 strain by compensating for its iron-acquisition defects6
Patients and pathogens are ecosystems; you need to understand both of them, or you don’t understand either.
- Even rabies virus, for example, which kills well over 99.999% of the people it infects, has had a half-dozen people survive. Myxomatosis virus let a few rabbits survive, and their progeny became relatively resistant; there are a handful of long-term survivors of HIV treatment; and when we get down to things like ebola and smallpox, 10-30% of infected people survive.[↩]
- Steve Silberman’s twitter account first drew my attention to the report.[↩]
- The quest for iron is a constant struggle for pathogenic (and other) bacteria, and they have evolved all kinds of mechanisms to seize it from the host, while at the same time animals have evolved more and more ways to keep iron away from invading bacteria.[↩]
- Note that this is speculation, not proven![↩]
- He also had diabetes, which may have made him more susceptible as well[↩]
- Centers for Disease Control and Prevention (CDC) (2011). Fatal Laboratory-Acquired Infection with an Attenuated Yersinia pestis Strain — Chicago, Illinois, 2009. MMWR. Morbidity and mortality weekly report, 60 (7), 201-5 PMID: 21346706[↩]
I know tons of people who work with BSL2 organisms who’d probably be a little disconcerted to hear this sort of news.
Offhand speculation: would regular blood donation be prophylactic in instances such as this?
Opps, I just realised my speculation sounds like bloodletting.
[...] the most lethal pathogens we know of don’t kill every single infected individual.1. Sometimes this is because the pathogen that infects the person is relatively weak. Sometimes [...]
[...] Mystery Rays from Outer Space has an interesting discussion on microbe-host ecosystems. He focuses on a report this week in MMWR of a scientist infected and killed by a strain of Yersinia pestis that should have been attenuated / rendered harmless. The same issue of Morbidity and Mortality Weekly Report (MMWR) (Feb 25 issue) has another atypical case of plague transmission where they conclude that a dog flea was the most likely vector. [...]
Interesting observation on the intrinsic weakness of certain individuals to certain pathogens. The beauty of nature, right?
Given this case do you think this will change laboratory safety policies for those working with pathogens that are considered “harmless”?
Super infection are my biggest concern. i think health care has went a totally wrong direction and became really monetized. anything that deals with money is bound to face ethical issues.:(
Some people still don’t grasp the strength of genetics and what a huge effect it plays in matters. It would be interesting, too, if they mentioned any ability of developing immunity, etc.
thanks for post..
Conceivably, hemochromatosis-induced iron overload might have a similar effect, enhancing the virulence of the infecting KIM.whether this causes a very dangerous for people?
good information
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This article offers an important argument to the endless struggle with chemical compounds that are deemed safe by the FDA. They will consider the actual compound but not the various possibilities as that compound mixes with common pollutants in the environment. If that wasn’t enough, you then throw in some genetics for good measure and its no surprise diseases run rampant.
“Some people are genetically resistant to HIV, because they have a mutated receptor…”
I say…., this is a very interesting article…, full of many information…., for me… I was almost believe that no one can stand against HIV…, as rumors say it is a punishment from God for those who love free-sex…
We have a lot of mosquito in our area. Please suggest some anti mosquito spray and chemical for domestic use to get rid of them. I shall be very thankful to you. I think your next post must be about the cure of the diseases caused by mosquitoes.
Interesting article describing the interaction between organisms and humans. In infectious disease epidemiology, there is a third component: environment. The environment, i.e. the factor that causes or allows the transmission of disease, is also important to understand. For example, mosquitoes carry the malaria parasite. So a susceptible host may develop malaria if bitten by a carrier mosquito. However, Plasmodium falciparum and Plasmodium vivax,two species of parasites that cause malaria, can only develop in mosquitoes when the temperature (environment) exceeds 64 and 59 degrees Fahrenheit, respectively. So, at least theoretically, even if one was bitten by a carrier mosquito when the temperature was lower than say 50 degrees Fahrenheit, one should be safe from malaria!
Definitely an interesting article on genetics effecting immunity. I have to say as aside though, I LOVE Steve Silberman’s Twitter. He posts really interesting of all different kinds from MMWR to Pink Floyd reissues.
HEy nice way to tell people about the relation between an individual and pathogen.but you are saying not all pathogens harm the infected individual but some do harm in an adverse way.
So be protected-stay away
I feel like the concept of “Black Plague” has been popping up everywhere recently. Really creepy stuff when you think about the enormous death toll. The “Stuff You Should Know” podcast had an episode recently all about the Black Death.
I’m already enough of a hypochondriac…!
Does anyone know if there have been any studies concerning the anti-biotic tracing gene placed in genetically modified foods and its possible effects on antibiotic resistance>
Your CDC job seems to be interfering with your blogging. Too bad, I enjoy your comments on HIV.
I always believed that a person’s ability to thwart off illnesses, pathogens, and any inflammatory process had a strong genetic component. Although we may be born with certain predispositions and propensities for different diseases, it doesn’t mean we can’t stem the tide through a anti-inflammatory diet coupled with light-to-medium intensity exercising. I also believe the less stressed we are, the less inclined our genetic predisposition will rear it’s ugly head. Very interesting article, thanks.
Very interesting topic. I didn’t know that studying about pathogens could be very interesting. Every person has different genetic make up and so I think that explains why there are some people who are more susceptible to pathogens while others got immune to it already.
Hmm.. interesting. I didn’t know that the genetic make-up of a person plays an important role on how he responds to pathogens and the like. It may be a big factor in terms of our immune system but I didn’t know for sure that it has a direct connection on how exactly our body responds to pathogens. Just thinking.
The body contains many natural orders of defense against some of the common pathogens. In the form of the human immune system and by some “helpful” bacteria present in the human body’s normal flora. However, if the immune system or “good” bacteria is damaged in any way (such as by chemotherapy, human immunodeficiency virus (HIV),
I do understand that the body possesses natural defense against some pathogens. In fact our antibodies automatically respond once they encounter intruders in our system. But I honestly think that there isn’t much proof that would convincingly link this to a person’s genetic make-up.
This is true. Not exactly the pathogen, but our weak immune system. As much as possible, we have to do something to make our immune system stronger. Health is wealth, we can’t afford to be sickly.
Hmm.. interesting. I didn’t know that the genetic make-up of a person plays an important role on how he responds to pathogens and the like. It may be a big factor in terms of our immune system but I didn’t know for sure that it has a direct connection on how exactly our body responds to pathogens. Just thinking.
Does anyone know if there have been any studies concerning the anti-biotic tracing gene placed in genetically modified foods and its possible effects on antibiotic resistance>
Definitely an interesting article on genetics effecting immunity. I have to say as aside though, I LOVE Steve Silberman’s Twitter. He posts really interesting of all different kinds from MMWR to Pink Floyd reissues.
Thanks for sharing this.Nice way to tell people about the relation between an individual and pathogen.but you are saying not all pathogens harm the infected individual but some do harm in an adverse way.Health is wealth, we can’t afford to be sickly.
Pathogens are organisms that cause diseases and it is actually a national health issue. They can be spread through air, water, food or blood. But not all pathogens have the same severity symptoms. We can’t really avoid this kind of virus. All we could do is to make our immune system stronger.
Yes, we just need to keep healthy. Eat the right foods, exercise and keep our weight down. This should help us keep our immune system stronger however, no-one can guarantee anything. Everyone needs a little bit of luck too!
stop smoking, less beer, no drugs, more exercise, eat organic healthy food, sleep early and be happy will be good enough.