Have you ever heard about the terrorist attacks of anthrax via mail in 2001 in US that finally ended with Bruce Ivins, the chief suspect in those attacks, committing suicide?

What about tracing microbe sources as in the Salmonella US outbreak?

This is microbial forensics.

Microbial forensics uses biological analysis such as genome sequencing, protein and carbohydrate fingerprinting to figure out the source of a biological agent. 2001 was not the year which witnessed the emergence of microbial forensics. Actually, in 1998 a doctor from Louisiana, who intentionally infected his former mistress with HIV, had a trial in court. But the anthrax attacks were really the reason for the amplification of the role of microbial forensics as it was followed by government funding and developing the sequencing techniques into more cheaper ones.

As a result, microbial forensics is extrapolated to further applications beyond biocrimes. In molecular epidemiology, it will help figuring out the source of food or water borne diseases such as in recent US Salmonella outbreak. The field also is expected to provide help in hospital-acquired infections. Many people sue hospitals every year claiming they got MRSA (methicillin-resistent Staphylococcus aureus) infection from a certain hospital. Tracing the source of the infection will prove whether those people really contracted the infection from the hospital or from any other outside source.

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Reference: Ontogeny