Final answer:
The change in Enrique's behavior is most likely due to a serious illness, such as HIV/AIDS, which is supported by symptoms like diarrhea and weight loss and his own concerns about the disease. The evidence presented does not strongly suggest that the change is due to mental health issues, sleep deprivation, or dietary problems.
Step-by-step explanation:
The strange behavior and change in Enrique could be attributed to several health-related causes. However, given the symptoms of diarrhea and weight loss mentioned in the extracts provided, and considering that Enrique had brought up concerns about AIDS, the most likely cause of his strange behavior and health decline seems to be related to serious illness, possibly an infection like HIV/AIDS.
There is also a mention of Enrique thinking he had a bad flu before being hospitalized, which adds to the suspicion that his change in behavior could be due to an immunocompromising disease rather than mental health issues, sleep deprivation, or dietary problems.
However, without further medical information, it is impossible to diagnose Enrique's condition definitively. The provided information suggests that Enrique was dealing with a health issue that had significant physical manifestations and was severe enough to lead to hospitalization.