840539006 is the ID by SNOMED https://www.snomed.org/news-and-events/articles/march-2020-i...

It comes from SNOMED, which is a system for electronic health records and is very comprehensive, multi-lingual & multi-national. Every disease, symptom, medical term, etc... has a code which allows matching across languages.

I doubt the IDs start at 1, it's likely the fist few digits (perhaps 8405) are a type classification for the ID. It's been going for a few decades and thousands of new IDs are added each year.

The complete list of codes can be found in the github repo containing the schema for the qrcode data https://github.com/ehn-dcc-development/ehn-dcc-schema/tree/r...

It's the SNOMED code for Covid-19

Yeah, Covid nineteen! Where was all this foofarah the first eighteen times, eh? Eh?

/s