ABC spoke to Dr. José Rafael Marquina, a Venezuelan native who has lived in Florida for the past 20 years. Marquina made a name for himself by publicly analyzing Venezuelan President Hugo Chavez's recent bout with cancer. He claims to have sources with information of Chavez's health, and now of Castro's.

ABC reports that Chavez traveled to Cuba yesterday to get a health check-up and to visit Castro (no other media appears to confirm this). 

Marquina claims that Castro "has suffered a massive embolism in the right brain artery," and is "dying." It's unclear where exactly Marquina is getting his information, though it's the latest in a string of rumors that Castro's health has seriously declined. The fact he did not publicly congratulate Chavez on his reelection last week further spurred speculation. 

Castro hasn't so much as released a public word since June. So, today, state-run newspapers published a letter supposedly written by Castro in which he congratulated doctors graduating from a medical academy. Not everyone is buying that Castro actually wrote the letter. The retired dictator hasn't been seen in public since earlier this year when he greeted the Pope.