Biosurveillance, in the context of biosecurity, is the detection and monitoring of biological agents to prevent biological threats. This is most commonly associated and achieved via metagenomic sequencing, the readout of the totality of nucleic acids (DNA and RNA) present in an environmental sample.
A prominent biosurveillance implementation is BioWatch, a US federal program designed to detect the release of known pathogens in 21 American cities. It mainly focuses on detecting airborne releases and subsequent PCR-based testing against a list of candidate pathogens. BioWatch has, however, been criticised for failing to respond to known threats while sounding false-positive alarms.
An unbiased, metagenomic sequencing-based proposal is the Nucleic Acid Observatory. It aims to detect any changes in the presence and composition of nucleic acids in major waterways and sewage, thus recognising emerging pathogens as early as possible.