Modern Disease and Mobility

Random thought of the day:

I have hear a fair amount of speculation regarding the causes of modern diseases (including cancers and various autoimmune disorders), Some of the more popular theories I have read tie it to diet, or to the increased use of chemicals, pesticides, etc.. (one more recent theory I mentioned in a previous post suggest a link between 1st world poverty and modern disease).

Of course, some of these seem unlikely, because the timelines don't really fit. For instance the assertion that the introduction of Grains, or the agricultural diet is the cause. The modern disease timeline goes back hundred of years, agricultural diet goes back thousands. The processed foods, or pesticides argument is closer, though there are still some holes in the correlation.

But I just had a random thought this afternoon. What about modern mobility? We have, and take advantage of an increasing ability to traverse in large numbers over vast distances. A simplistic but supporting example:

It has been reported that small, isolated groups tend to have less disease. a family, living in complete isolaion, for instance. However, if they come in contact with other groups, they tend to have low resistance the bacteria and virii those visitors are carrying with them. This was considered to be a major contributor to the decimation of native american populations when Europeans arrived in the new land. Native Americans lived primarily in smaller tribal groups, with relative isolation, and limited travel. Their immune systems weren't prepared for the disease the white man brought from Europe.

But if that were the case, why then were the pilgrims not equally decimate by Native american diseases? Much of it may be explained by the points in this article- in short the introduction of rats (specifically the black rat) and fleas as carriers/transmitters, and comparatively poor hygiene of native american populations (respecting soil, water and food).

But what if there is something else that plays in as well? What if there is a (complicated) equation which can be derived, relating...

Population Size
Population Mobility
Range of Mobility
Viral and/or bacterial interactions relating to population, distance, and time

vs. rate of adaptability of the human immune system?


(Yeah, probably some multi-variable calculus involved in that).

What if, with our increasing ability to traverse increasingly large distances, in increasingly shorter times, we have created an environment in which our immune systems simply can't evolve fast enough to keep up with the intermingling and evolution of bacterial and viral strains?

That was my random thought for the day.