If any, it has mostly been through contact with contamination in the water or on the turtle itself. The causative agent is usually Salmonella or E. coli.
Very recently, an Australian veterinary student reported the country’s first known case of a captive turtle acquiring a highly infectious disease caused by a mycobacteria which could potentially spread to humans. The turtle ultimately died. Such cases have also been documented in the US.
People who keep turtles as pets should be careful and learn how to recognise the symptoms and treat them before they start to spread.
How do people deal with dead turtles?
Scientists will perform a post-mortem on dead turtles to find out the cause of death. They will keep samples of tissues for further analysis. A layman should try to inform the authorities if they ever encounter dead turtles stranded on the beach. Documentation of such cases will help elucidate patterns of mortality, etc. We have encountered dead turtles stranded on beaches in Terengganu several times and most of them were probably killed in fishing gear. A picture of Azimi and Fong helping with a dead green turtle is posted above.