Unless the samples are going to a lab for Gene Sequencing how does anybody know which variant they have.
A subset of all COVID tests are sent for sequencing.
It isn't easy to learn how many samples are sequenced and how many are sequenced AND sent to GISAID. I found this with a bit of searching:
Country - Percentage of cases sequenced
Iceland - 56%
Denmark - 47%
Australia - 21%
Luxembourg - 20%
India - 15%
Norway - 13%
USA - 3.6%
Not surprisingly, in the US, it varies widely by state.
In California:
August 2021, 16%
July 2021, 23%
NOTE: In California, these are the number of sequences submitted to the data repository GISAID and is not a complete list of sequences completed to date.
In April 2021, the US ranked 33rd in the world in terms of the percentage of COVID-19 cases sequenced, up from 36th a few weeks earlier.
The USA has over 60 labs capable of doing the sequencing for the CDC's national strain surveillance network. One lab, the Mako Medical Lab in North Carolina is sequencing 30,000 samples per day.
Good point.