We dont test everyone to get the generic flu statistics. CDC estimates the number of unreported/untreated cases. Without knowing what goes into the CDC estimates, I dont know how they arrived at the 38 million estimate, but I am sure it is informed by many years of experience and testing.
We dont have extensive data on the Wuhan virus, but our testing capability is expanding exponentially by the day. We have tested well over 300,000 to date. As the database expands, so will our knowledge of the virus. Testing for antibodies will give us more information.
A lot of people have symptoms and dont seek medical help. I believe I had the virus in late December along with my daughter who had the same experience. We both had the flu shots and never had the flu. This time I woke up with a sore throat that lasted a day followed by a low level fever for 3 or 4 days and lung congestion, fatigue, and aches and pains. My daughter went thru the same cycle about a day behind. I decided to go to the doctor the next day, but never made it because the symptoms cleared up the following morning. My illness was not recorded officially. The only way to ascertain I had the virus or the flu is thru an antibody test.
Based on limited US testing, about 90% of those tested are negative for the virus. The vast majority of these people had symptoms. NY is an exception with about 40% testing positive for the virus. The bottom line is that we need more data to draw any significant conclusions. When the dust settles, the US will have the most extensive testing data in the world.