Origins

Hello everyone and welcome back! This semester I’m enrolled in a journal club class that will meet weekly to talk about scientific papers that pertain to microbial pathogenesis…or in other words, the way in which disease develops. This past week we discussed a paper that addressed the origins of some major human infectious diseases.

Every piece of scientific literature tries to communicate something, or rather, has a purpose. The purpose of the paper we discussed by Wolfe et al. 2007 (for reference in case anyone reading would like to view it later), was to show that there were differences in the origins of diseases that are/were prevalent in temperate climates, in compared to tropical ones. If you are a student, can you name two diseases that are prevalent in your home town or country?

They suggest that New World (the Americas) diseases came about through the rise of agriculture, and highlight five intermediate stages of pathogen infection of other animals. Remember that a pathogen is defined as a bacterium, or some other microorganism, that can bring about disease. Research is often interconnected with other disciplines, and so this work is not only important for microbiologists, but for historians and evolutionary biologists alike.

Interestingly the persistence of these diseases is dependent on several factors, including rate of infection of new hosts and host population density. The authors specifically looked at data pertaining to 25 diseases, but selected 17 of them based on factors such as current or historical world burdens. Such diseases include HIV, tuberculosis, and smallpox.

Well…what do they find? Here, the differences they see in temperate versus tropical diseases, include vector transmission rates, and type of infection (chronic versus acute for example). The word ‘vector’ refers to another organism that carries a pathogen that can later infect you! Good examples include mosquitoes, or even sand flies. A chronic disease describes one that lasts for a long time. An acute disease is much more short term.

Also, most temperature diseases are described as ‘crowd epidemic diseases’. They see that more temperature pathogens have origins from domestic animals, in compared to tropical pathogens, and may be due to difference in lifestyle (for example in terms of livestock domestication).

Lastly, they seem to address that most diseases that affect humans, are derived from pathogens of other vertebrates, with the exception of two cases of the avian (bird) variety.

In summation, apart from Chagas disease (which I will talk about next week), the diseases of the analyzed database seem to originate from the Old World (Africa, Europe and Asia), rather than the New World (the Americas). This kind of research can ultimately help in the understanding of emerging infectious diseases, as well as its control and detection.

Take care until next time! 🙂

Follow the links to read more on pathogenesis, pathogens, chronic disease, Old World and vector. Credit given for use of sand fly image, smallpox giant microbe and pathogen cartoon.