Infectious Disease: Evolving Challenges to Human Health

Evolving Threats to Health

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Random Mutations + Natural Selection = Evolution

“The tremendous evolutionary potential of microbes makes them adept at developing resistance to even the most potent drug therapies and complicates attempts at creating effective vaccines.” – IOM 2003

Evolving Threats to Health

Evolution is a continuous process in which an individual with an altered gene survives and propagates better than others. New genetic traits appear randomly, but the environment selects for individuals with traits that help them survive and grow. Individuals with these traits will become more common.

Microorganisms have extremely rapid reproduction rates and some even have higher mutation rates. Both characteristics give them an evolutionary advantage. Microorganisms can go through thousands, and possibly more than one million generations for every human generation. Therefore, individual microorganisms with mutations appear much more rapidly.

Some microorganisms, such as hepatitis C virus and HIV, are particularly prone to mutations when they replicate their genomes. Some mutants are sufficiently different to the original infecting virus that they are not recognized by the immune system.

Rapid and constant evolution challenges our main defenses against infectious diseases, which include
- public health measures that minimize exposure to disease-causing organisms;
- immunity, whether gained by infection or vaccination; and
- therapeutic drugs used to treat infections.

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Rapid Evolution
Watch the continuous process of evolution starting with a single E. coli bacterium.
Text-only version

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Exponential Growth [next]