Spencer asked me to post this response:
When we say that a test is 98% accurate what we mean by that is that if you have the disease the test says you have the disease 98% of the time, whereas if you don't have the disease it says you don't have the disease 98% of the time.
Out of every 1 million people, 1 will have the disease, but 2% of those 1 million will be falsely told by the test that they have the disease
so if all 1 million people were tested, there would be roughly 20,000 people who were told they have the disease but don't have it, and 1 who was told they have the disease and do have it
so about 1/20000 people who are told they have the disease really have it
not anywhere close to 98%