Thread by @MackayIM

Some thoughts on wastewater (sewage) testing...
💩Usefulness?
Of most benefit when used in an area with no known cases. Lets us look for a signal that virus is somewhere in that region. Pop-up testing may then be deployed to get a better idea of the situation

💩Mature technology?
Methods/usefulness still being evaluated.
What does a positive mean? How often are false negative/positives likely? Which PCR-based tests are best? What processes in place to confirm wastewater positive result & what response will that trigger if confirmed?

💩Do all agree?
Full spectrum of responses to wastewater testing, from exuberance to dismissal. I think time and continued refinement of the methods will tell which was the best position. As with everything in this pandemic, we're learning many new things as we go.

💩What does a positive result mean?
We do need to be aware of all the potential sources of virus that may pour into *that* wastewater pipe/plant. The result doesn't automatically mean community cases are walking about.

The source may be a hotel used for quarantine, a traveller passing through or ocean liners emptying their waste tanks at a 'pump ashore' facility along a coast.
There can be much more to interpreting positive results than meets the eye.

💦I think we should be using this approach in places like NZ and Australia because we are mostly free of community COVID-19 transmission. We should use and keep refining the methods if needed & respond to any positive findings in context & alongside good public communication.

💦Wastewater testing is also useful for surveilling other viruses for example the enteroviruses or parechoviruses (I wish!). And for virus discovery where it has had worldwide success in the past.