Common things being common, viral illnesses over this past holiday season (weird thinking and saying that now, seem so long ago and far away) were predominately influenza, and we saw some sick ones this past winter. As for immunity after COVID infection - the answer is we don't know. We hope so in that convalescent serum from those recovered seems to contain neutralizing antibodies. However, there is really no way to know for sure because having neutralizing antibodies is only one step of many in developing "long term memories" in your immune system to remember it the next time around. The molecular immunology is very complicated, but it comes down to developing the right type of neutralizing antibody that your body has the ability to "remember" for next time around. Not all neutralizing antibodies do that. In fact, most don't. And we couple with that with anecdotal reports that people are getting repeat symptoms and testing positive again after they had recovered and tested negative. So, the answer is, we don't know. As for testing to see if you were infected in the past. Yes, IgG antibody testing is being developed, alongside vaccines. IgG is the "long term" antibody after an infection. Keep in mind I'm using the words "long term" very generally in laypeople's terms. "Long term" antibodies (IgG's) does not mean they are the correct antibody that will be remembered/ramped up and protect you next time around. A prime example is Hepatitis C antibody - the antibody your body naturally develops against hepatitis C hangs around just about forever, but offers absolutely no protection against re-infection for those who clear it naturally the first time around (about 1/3 of them do).