When a virus such as the flu is going around, the earlier it's detected, the better prepared that health agencies can be. It's with this in mind that scientists at Stanford University are pursuing an idea. They're proposing doing analyses of communities' wastewater to detect rises in the amount of viruses passed by residents, identifying the microbes based on their DNA.

The idea is that municipalities would regularly analyze their raw sewage stream, checking the liquid for the DNA of pathogens that have gone down the toilet. An increase in those levels would indicate that an outbreak was about to begin, before people actually started reporting symptoms. This would allow preparations to be made and warnings to be issued, that much earlier.

A team led by Prof. Craig Criddle is about to begin testing the feasibility of such a system, by analyzing the sewage at a plant that treats waste generated by approximately 7,000 people in the Stanford community. Needless to say, some challenges are anticipated.

For one thing, the automated sampling system will have to compensate for the fact that the volume of waste varies greatly depending on the time of day. Additionally, waste flushed farther up the line will be much more diluted than that introduced closer to the plant, so levels of viruses in it may be appear to be lower than is actually the case.

Nonetheless, Criddle believes that the proof-of-concept model will ultimately be effective.

"We can understand things that are happening to the community and take measures to address those concerns, whatever they may be, in a more timely way than would have been possible otherwise," he says.