What is the ancient Egyptian 'mummy's curse'?

Within months of the discovery of King Tutankhamun's tomb in 1922, the man who financed its excavation — George Herbert, the fifth Earl of Carnarvon in England — became ill and dropped dead. It didn't take long for people to question whether a "mummy's curse" had doomed the earl.

"Pharaoh's 3,000 year-old Curse is Seen in Illness of Carnarvons" read the headline on the front page of the March 21, 1923, edition of "The Courier Journal," a newspaper published in Louisville, Kentucky. 

Similar headlines appeared in newspapers around the world as news broke of Carnarvon's illness and death. He suffered an infection that reportedly resulted from a shaving accident when he cut a bite mark made by a mosquito. Reports claimed that his wife, Almina Herbert, was also ill, but she recovered and would live until 1969, dying at the age of 93. 

Despite Almina's longevity, her husband's death raises a question: Is there any evidence supporting the concept of a mummy's curse? 

Related: How do we decipher Egyptian hieroglyphics and other ancient languages?

Carnarvon had been financing the search for and excavation of Tutankhamun's tomb. When Howard Carter found the tomb in November 1922, he delayed exploring inside until Herbert could arrive from Britain. After Carnarvon's arrival, they ventured into the tomb, seeing the "wonderful" artifacts buried with Tutankhamun. No writing from ancient Egyptians mentioning a curse was found in the tomb. 

While the notion of a "curse" may sound ridiculous, it has actually been studied seriously by scientists, with several papers published on the topic. In an effort to determine whether a long-lived pathogen could have caused the "curse," scientists used mathematical modeling to determine how long a pathogen could survive inside a tomb, according to papers published on the subject in 1996 and 1998 in the journal Proceedings of the Royal Society B: Biological Sciences.