Researchers have discovered that the Streptococcus bacterium acquired its "flesh eating" toxic shock power after an infection of its own from a bacteriophage, a form of virus that attacks bacteria, about 30 years ago. The bacteriophage inserted a gene into a strain of the strep bacteria that allows it to take the human plasminogen protein and convert it into the protease enzyme. This enzyme destroys the human tissue, enabling the rapid invasion of the body that characterises the vicious nature of this strain of strep.

The mutation also produces an enzyme which allows the bacterium to escape capture and death by the host body's white blood cells, or  neutrophils. This selects the mutated bacteria over their less virulent cousins without the gene. It's a gruesome example of evolution in action.

The Sydney Morning Herald recently carried an article entitled High altitude flights spark symptoms. It referred to a study of the Effect of Aircraft-Cabin Altitude on Passenger Discomfort published in the New England Journal of Medicine. The study found that the reported rates of discomfort increased greatly at simulated altitudes above 2100 metres and durations between 3 to 9 hours. The onset of acute mountain sickness did not appear to depend on the altitudes studies (between 198 to 2438 metres) in those that experienced it (17.4%).

I believe that I experienced altitude sickness on flights with Malaysian Airlines and Asiana with severe headaches and nausea that improved upon descent to lower altitudes. It is interesting that this did not occur with all airlines (eg Qantas, Cathay Pacific) leading me to suspect that some airlines cycle cabin air more often (perhaps affecting the oxygen and carbon dioxide ratios) or keep their cabin pressure lower (although the study would seem to discount that). Both strategies save fuel. 

Prompted by last week's episode of House and a GP's comment that Rabies was the most painful vaccination to have (I think Smallpox might be worse) I did some reading on rabies.