Few factors to consider here if you want to consider the numbers a true representation
As you say you test more people you’re going to find more cases. But also have to remember the test doesn’t pick up all positive cases (60-70% ‘sensitive’). What this means is a negative test doesn’t mean you don’t have it.
This is proving a real problem in reality as there are patients who act like COVID patients, have the blood profile and the imaging of COVID patients but multiple swabs come back negative. In a small number it’s needed 3 or 4 swabs to get a positive result.
What this means is the case numbers are going to be underestimated further still. Remember also we’re only recording deaths where they managed to get a positive swab before they passed away.
Overall the numbers will give you trends but just be aware there are likely to be many more patients