I've noted previously that infectious causes of so-called"chronic" diseases--illnesses such as cancer, heart disease, and autoimmune disease--are an interest of mine. The Guardian has a nice overview of infectious causes of cancer--and why one can't simply "catch" cancer as you catch a cold. It's a much better article (or at least headline) than this one, which discusses recent findings that a few types of adenovirus could play a role in the development of obesity. However, this does not mean--as the headline suggests--that "obesity is contagious." You're not going to "catch fat." Even with infectious causes of these conditions emerging, they still are only part of the picture (which includes other environmental factors and host genetics).
(ETA: Check out this post over at Complex Medium for a bit more info on the microbe/obesity link.)
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Thanks for the pointer - my first experience with this is idea of long-term infection leading to mutation and cancer was when a stray cat I adopted developed a malignant tumor in her jaw after having an infected tooth for some months. Since you're a public health/epidemiologist: what's your take on the relationship between HPV and cervical or anal cancer? HPV infection seems really widespread.
I am in agreement that there is much more than just a virus involved in getting cancer. The Tasmanian devils (google it) on one part of Australia are getting cancerous tumours by biting each other. The other Tasmanian Devils on another part of the island have a genetic difference that makes them seemingly immune to the cancer that is prevalent in the other type. That was out yesterday I believe. As an epidemiologist is it POSSIBLE that cancer cluster that were blamed on environmental factors only could have been triggered by a bug, the environment, genes and something else as opposed to just ONE cause? Would that explain a cluster effect of cancer if there is a component affected by bugs?
Indeed it is, but only a few serotypes of HPV have been found to cause cancer. That's one thing that makes these connections difficult to figure out sometimes--it may just be a limited number of genotypes of pathogen that cause cancer (or obesity, in the adenovirus example--most adenoviruses haven't shown this correlation with weight gain). So if, say, one does a serosurvey looking only for antibodies to a pathogen and trying to correlate that with a diseae like cancer, they may (falsely) see no connection because it's only a limited group of the pathogen strains that cause the cancer (or other chronic disease).
impatientpatient--re: Tasmanian Devils, afaransis has a post on that here.
Yep. In fact, there's been some recent studies on a cluster of childhood brain tumors in England that has hallmarks of an infectious disease, rather than a more commonly-blamed environmental factor (pollution, radiation, etc.) And almost all of these seem to involve host genetics as well. For instance, I first got interested in all of this by looking at the epidemiology of multiple sclerosis, which is thought to have some kind of infectious component. However, it's much more common in people who have a certain genotype (based on their MHC haplotype--long story). So the development of disease is a factor of pathogen genotype + host genotype + probably other factors (nutrition status, other infections, etc.) It's a challenging field, but one that's beginning to become easier to navigate thanks to easier genetic screening tools.
Thank you. You are so prompt in reply to all questions and I appreciate that. I am so curious about these things that sometimes I forget that other people might not be as enthused OR they have lives too. I think that these possibilities of diseases, that were attributed to so many other factors , may be caused by pathogens that were undetectable before are fascinating. I have a vested interest in this, in the sense that I am a layperson who is infuriated by the psychosocial model of disease, rather than physiological/biological explanations. I have seen too many people die or suffer from diseases that they have been blamed for- If you only had more hope your cancer would have disappeared, if you only were less stressed your ulcers would go away- etc....that this is heartening to see that these constructs are proving to possibly or concretely be false. I hope you don't mind my questions. I am a non scientist asking questions far out of my "specialty" which is education of young children, and I appreciate you taking my questions, with all my mistakes and non technical language, and answering them thoughtfully.
Don't mind at all--questions are a good thing. Make me think, too. :)
"Indeed it is, but only a few serotypes of HPV have been found to cause cancer. That's one thing that makes these connections difficult to figure out sometimes--it may just be a limited number of genotypes of pathogen that cause cancer"
Remember the upside of that however, it makes things a lot easier to make a vaccine for :D
Also on the devils, didn't they find that the cancer they are spreading is some sort of 'infectious' cancer? I recall reading something that seemed a little crazy that the current idea is when they bite they pass on cancerous cells. These cells then establish an infection in the other devil and so it goes on. Of course, I wouldn't be surprised if it's just a virus but it would be really fascinating to have an infectious transmissable cancer.
But I'd put money on a virus just in case ;)
From what I understand, they didn't find a virus involved in the Devils case--it appears to be direct inoculation with the cancerous cells that's doing it.
Is this like catching warts?