Can I just say how geektastically awesome it is that we're having a discussion about how to frame claims about Wikipedia's popularity? Now this is what lists are FOR.
But in the interest of avoiding
stasis, I also want to say to Lane: don't sweat the language too much ;) You're not going to be spouting untruths or despoiling the brand if you say Wikipedia is the, or one of the, highest trafficked websites in the world for health info. Wikipedia researchers make claims like that frequently, and often with less data to back it up than you're offering.
Also, Lane: do you want someone to script up that pageview request? I agree with Erik that using WP Med/WP Health categories will get you better results. I've been on the hook for getting some similar data for Biosthmores for about... 6 months now. I could work on it on my own time some evening this week.