Long story short, the UTMB bloodmobile would not accept blood from donors who had been to the ruins at Tulum within the last year. It seems there was a malaria outbreak there, and the mosquitos at the ruins are carriers of the virus. This ban applies only to people who have visited the ruins at Tulum, so if you visited Xel-Ha or anywhere else on the Mayan Riveria, you are supposedly safe (although I do not recall seeing a mosquito net around the ruins at Tulum).
I am passing this on as FYI to those who have visited or may be planning to visit the Mayan ruins at Tulum, as I do not recall Carnival or the Mexican tour guide issuing any warnings to passengers that visiting these ruins might be hazardous to your health. At best, you will be disqualified from donating blood for one year after your visit, and at worst, you may contract a case of malaria. Therefore, if you are planning on visiting Tulum, I would take some insect repellent with a high DEET content (Deep Woods Off) for the mosquitos, just to be on the safe side. Take care all !!
until honeymoon cruise on Elation