What caused a Spanish tourist to pass out in the Great Pyramid? Could it be the Curse of the Pharaohs?

People first started believing in the Curse of the Pharaohs when British Egyptologists found Tutankhamen's tomb in the 1920s and Lord Carnarvon died mysteriously shortly thereafter. What's the scientific explanation for his untimely demise?

The Curse of the Pharaohs has apparently even struck people who have never entered the Egyptian tombs and was cited as the reason for the sinking of the Titanic.

None of the explanations behind the Curse of the Pharaohs have been definitively proven as not everyone who has entered the tomb has succumbed to its fate. What are we to believe?