Disease

I watched an interesting talk today about the possibility of controlling the evolution of infectious diseases.
A few years ago cholera was introduced to Peru, causing an outbreak, and it spread to neighbouring countries such as Ecuador and Chile. But the severities of the outbreaks were very different because these countries have differing qualities of water supply.
The interesting finding was that not only were the severities of the whole outbreaks different, but that the cholera strains had evolved to be milder in places with cleaner water because they needed healthier, more mobile humans in order to be transmitted.

A similar thing could be done for both malaria and HIV; insect-proofing housing in malarial regions would prevent mosquitoes biting severely ill people, and thereby reduce the spread of virulent strains of malaria. A reduction in HIV transmission rate would make HIV evolve to be less aggressive.

For HIV, spread by direct contact, a reduction in contact is always a good thing, and so this theoretical possibility does not suggest a new way to improve HIV care. But in vectorial diseases we have a powerful way to improve the disease.
If microbes in hospitals become resistant to antibiotics they will often be more virulent. If we can identify major routes of transmission and block these preferentially for the most virulent strains (which are easily identified by the worst suffering patients) then this action will not only be directly protective, but preventing some infections, but will introduce a reproductive bias in favour of less aggressive infections.
We need to identify whether transferring patients to specialist wards provides more opportunity to spread infection or reduces it, and whether patients then all share the worst strain on that ward.
Perhaps specialist wards should deliberately take only half the cases, and try to take the worst ones, in order to make the infections evolve to be less problematic, rather than treat one species as all the same.