> This doesn't add up either -- immunity per individual is expected to last 'only a few months',

There is no evidence either way. Even if it is transient it will be enough for it to die down

There's some very strong indicators that immunity will be ephemeral.

It's possible the R naught will drop below the currently assessed 2.2 over time, but there's no evidence for that -- and if both these things stay as expected, it won't be transient enough to 'die down' naturally.

Unfortunately until we get an antigen test, we will not know for sure. But there is no reason to believe at this point that it isn't anything other than a standard immune response.

It would extremely rare that it wasn't

There's no indication how long the immunity is expected to last. It's just as likely that immunity, even if temporary, can last for a year or more, as is the case with the flu or some other viruses.

On HN this morning -- news that someone in Japan is already on their second infection of this virus.

So there's our first data point.