It has been claimed that Pinzón's recurring fever was syphilis. The theory that syphilis is of New World origin and that it was first brought back to Europe by Columbus's crew has been longstanding, and long controversial. Some recent genetic evidence restores credence to the theory. Even so, even if Pinzón contracted it on the voyage, it is extremely unlikely that it was the cause of his death. Tertiary syphilis does not normally show up for 3 to 15 years. There is also a possibility that some historians have confused Martín Alonso Pinzón with his brother Francisco, who is more plausibly (but still controversially) believed to have had this particular disease. Conversely, there is the possibility that the first outbreak of syphilis among Europeans with no immunity was much more virulent than subsequently.