Also, the number of “Confirmed and Probable” cases is a small percentage of actual cases. Many people with the flu never see a doctor, and of those who do, very few get the lab test needed to make a confirmed diagnosis of H1N1.

CDC flu expert Dan Jernigan last week estimated that about 100,000 people were sick with the flu, about half of those with H1N1, and it is continuing to spread. The good news is that as the number of people sick with H1N1 goes up, the CFR is even lower than reported.

In the U.S., the Case Fatality Rate from the 1918 influenza pandemic is estimated to be 1.9%, not 0.5%

The definition of a “confirmed or probable case” involves testing a specimen from the sick person in a lab. In the first weeks of this outbreak, only one lab in the US could confirm a case, and that was CDC in Atlanta. After CDC distributed test kits and procuedures, there are almost 50 labs in the US which can confirm novel H1N1, so it’s not surprising the number of lab-confirmed cases continues to grow.

You are doing an excellent job with your blog and postings. I wanted to provide you wih some additional insights:

Item 4: You write “Now, I am not an epidemiologist, but to me this suggests that as the H1N1 virus has spread, it has become less lethal as it has mutated.” Problem is, although many speciments of this H1N1 have been sequenced, the molecular virologists are not finding any significant mutations, and the reason it seems to be more virulent in Mexico is unknown. I say “seems” because we rally don’t know how many cases there were in Mexico. This is important, because the case fatality rate (CFR) is number of deaths divided by number of cases. If 100 people died of H1N1 in Mexico, is that severe? It depends. If there were 200 cases and 100 deaths, that would be a CFR of 50%, very high and comparable to H5N1. If it were 100 deaths out of 100 million cases, that would be 1 out of a million . . and not much to worry about. Sinvce Mexico was not looking for cases before April, we know hown many people died in hospitals of H1N1, but we don’t know how many didn’t die. The Mexican CFR could easily be similar to that of the rest of the world, we just don’t know.

But one thing we do know, researchers have found no mutations which could account for a decrease (or increase) in lethality, and believe me, they are looking!