It's what we're here for :) as long as the stuff isn't going to waste it's all good!

For flu I've not heard of any plans to do so but it's a question I can ask. They have done it for covid and polio I know that much. I would presume as the flu surveillance program is so well established using clinical samples, it might be deemed unnecessary to test waste water?

Although from my own point of view, we actually don't get the full picture of how much flu/what types of flu etc are out there globally in a season because we only get clinical samples (I say only, we get thousands of them!). How many people are actually sick with flu, but don't need medical attention, thus not getting swabbed? It is something I've brought up in general discussion and there was agreement, but currently not much we can do about it.

This is actually a big question to answer because a lot of surveillance goes into it. It's not just about looking the past strains of flu which have been circulating and which strains went into the vaccines. It's also how the populations current immunity reacts to the circulating viruses in lab tests.

There are several WHO Collaborating Centres around the world which receive virus samples taken from positive flu cases sent by various National Influenza Centres globally. The virus samples are put into culture in the hope they grow, sequenced if they do and a genetic tree is made to see if there are any obvious outliers, strains to watch etc.

During this time there are calls for blood donations (usually from people who work in these places!) pre and post flu vaccination. The serum from the blood is sent to each WHO collaborating centre so they can be used to test against viruses which are circulating/deemed of interest.

All of those results are pulled together ready for the vaccine composition meeting which happens twice a year (the northern hemisphere one is happening this week, southern is normally September) and a decision is made as to which strains of Influenza A and B go into the next jab. Then the candidate viruses get grown up, and passed on to the manufacturers of the vaccines. This has a time limit, about 4-5 months before the new vaccines and reagents for testing them have to be sent to the WHO Essential Regulatory Laboratories (ERLs), to undergo strict quality control tests to ensure they meet the standards expected before being used in the public health care system.

This video actually explains it quite nicely if TLDR! Monitoring Influenza Around the World

You can also learn more about GISRS and the Global Influenza Program here https://www.who.int/teams/global-influenza-programme#

This is actually my job, I work within the GISRS network - used to be in an ERL, now a WHO CC.

Depends if there has been a strain change in the vaccine for either hemisphere. Some years it remains the same for both, in which case no you could probably just have the 1.