So how many H1N1 cases? 2 or 2000?

WSU reported this week they have had approximately 2000 contacts (visits or consultations) with students who have H1N1 influenza. And the Whitman County Health Department states that only two cases of H1N1 flu have been confirmed. This can't be right, can it?

Actually, both numbers are correct, and I will try to explain why.

Influenza viruses circulate around the Northern Hemisphere every winter. We call that Seasonal Influenza. There are Influenza A viruses and Influenza B viruses. Influenza A viruses have a lot of variation and are identified by a confusing set of letters (H,N) and numbers (1-7).

In April of this year, a new Influenza A virus appeared in Mexico and quickly spread around the world. This is the 2009 H1N1 Influenza A virus (formerly call 'swine flu'). 2009 H1N1 Influenza quickly became THE main influenza virus in circulation. Since May of this year, about 98% of all influenza viruses sampled from flu sufferers in the US and examined in laboratories has been 2009 H1N1 Influenza.

The hallmark symptom of influenza is fever. The fever is usually over 101 degrees and comes with a dry cough or sore throat. Body aches, headaches and a feeling like the roots of your hair are on fire frequently accompany the fever. These symptoms typically last 3-5 days then usually resolve without treatment.

Health care providers see enough patients with influenza every year they rarely need a test to confirm the diagnosis. Early in the regular flu season, doctors may test a few patients to convince themselves that what they are seeing is really influenza. After that, they don't spend money testing for the flu. If it looks like the flu, sounds like the flu, and acts like the flu, it's the flu.

And this is what has happened with the sick students on campus. A few students with typical flu symptoms were tested at the beginning of the outbreak and were found to be positive for Influenza A. We assumed this was 2009 H1N1 Influenza A from the outset. But since assuming anything is usually a bad idea, a few samples from sick patients were sent to the State Public Health Laboratory for further testing. As we suspected, the samples came back showing the infections were due to 2009 H1N1 Influenza.

So both numbers are right. In the past two weeks, up to 2000 students at WSU have complained of, or sought care for, symptoms compatible with influenza. That means a fever with a cough or sore throat. Only a dozen or so had tests showing they had Influenza A. And only two have had more extensive testing confirming the flu outbreak was caused by the H1N1 Influenza A virus - something we knew all along.