Dr. Jen Halverson just sent a comment to the post on PAHO's chikungunya update, and I think it deserves a post of its own:
I don't know how PAHO is getting their numbers, but anyone on the ground in Haiti will tell you there have been way, way more than 11,802 cases.
Among friends and people I know, I suspect that at least 50% have had an illness consistent with chikungunya (and in some families, everyone or nearly everyone has had it). This is both in Port au Prince and in many surrounding areas.
Among the women at the maternity center I work with, a significant percentage of the pregnant women are self-reporting that they've already had a febrile illness consistent with chikungunya.
None of the people I know in Haiti have had laboratory-confirmed chikungunya--it is all suspected--but the symptoms are so classic (and quite different from malaria), and dengue is much less common, so I think that among people who suspect they've had it, most of them have probably really had it.