A creature who, because of ability damage from a disease, reaches Constitution 0 is killed by the disease. If a creature has -10 hp before that happens, the creature has, instead, died from having -10 hp (usually via injury).

In your example, the wounds from battle killed him, not the ghoul fever.

Corner Case
Constitution (PH 9) says the ability modifier is added to "[e]ach roll of a Hit Die (though a penalty can never drop a result below 1--that is, a character always gains at least 1 hit point each time he or she advances in level), but later says, "If a character’s Constitution score changes enough to alter his or her Constitution modifier, the character’s hit points also increase or decrease accordingly."

Emphasis mine.

Thus, oddly--and, perhaps, luckily for those peasant villages beset by ghouls--, a creature with only a maximum of 1 to 4 hp can be at negative hp and subsequently die (were he not stabilized) despite still having a positive Constitution after contracting ghoul fever. Were that the case, I'd argue hp loss is still the killer (critical existence failure on the creature's part, perhaps?), not the disease proper.

A creature who, because of ability damage from a disease, reaches Constitution 0 is killed by the disease. If a creature has -10 hp before that happens, the creature has, instead, died from having -10 hp (usually via injury).

In your example, the wounds from battle killed him, not the ghoul fever.

A creature who, because of ability damage from a disease, reaches Constitution 0 is killed by the disease. If a creature has -10 hp before that happens, the creature has, instead, died from having -10 hp (usually via injury).

In your example, the wounds from battle killed him, not the ghoul fever.

Corner Case
A creature with only 1 to 4 hp could end up at negative hp and subsequently die despite still having a positive Constitution. Even then, I'd argue, hp loss is still the killer (critical existence failure on the creature's part, perhaps?), not the disease proper.

A creature who, because of ability damage from a disease, reaches Constitution 0 is killed by the disease. If a creature has -10 hp before that happens, the creature has, instead, died from having -10 hp (usually via injury).

In your example, the wounds from battle killed him, not the ghoul fever.

Corner Case
Constitution (PH 9) says the ability modifier is added to "[e]ach roll of a Hit Die (though a penalty can never drop a result below 1--that is, a character always gains at least 1 hit point each time he or she advances in level), but later says, "If a character’s Constitution score changes enough to alter his or her Constitution modifier, the character’s hit points also increase or decrease accordingly."

Emphasis mine.

Thus, oddly--and, perhaps, luckily for those peasant villages beset by ghouls--, a creature with only a maximum of 1 to 4 hp can be at negative hp and subsequently die (were he not stabilized) despite still having a positive Constitution after contracting ghoul fever. Were that the case, I'd argue hp loss is still the killer (critical existence failure on the creature's part, perhaps?), not the disease proper.