One hundred years after its discovery, the tomb of Tutankhamun remains one of the most famous archaeological finds of all time. Surrounding this fame is a mystery that has gripped the public imagination for decades and transformed the boy king into a pop culture icon: The curse of the mummy.

On November 4, 1922, in Egypt’s Valley of the Kings, British Egyptologist Howard Carter stumbled across a crumbling step, half hidden beneath the debris from the tomb of Ramesses IV. Digging further, he discovered more steps, leading to a sealed stone door.

Carter called on his sponsor, Lord Carnarvon, to join him at the site, and together they uncovered one of the most impressive finds in the history of Egyptology.

The tomb contained over 5,000 artifacts: gold, jewelry, food offerings and ornate statues. But treasure wasn’t the only thing that the archaeologists unearthed.

Five months after the excavation, Lord Carnarvon died, supposedly due to pneumonia and blood poisoning brought on by an infected mosquito bite. A month later, George Jay Gould, a wealthy American financier who had visited the tomb, died from the same affliction.

In 1924, British archaeologist Hugh Evelyn-White hanged himself, allegedly leaving a note that read: “I have succumbed to the mummy’s curse.” Later that year, the radiologist who x-rayed the mummy before it was given to museum authorities, died of an unidentifiable illness.

Within a decade, at least nine people with connections to the excavation had died. Many were convinced that this was evidence for the rumors of the mummy’s curse. But could there be another explanation?

In the 1970s, the 500-year-old tomb of a Polish King, Casimir IV Jagiellon, was opened for the first time at Wawel cathedral in Krakow. Within a few days of the excavation, four of the 12 researchers had died, and several others died in the months that followed.

Despite rumors of an ancient curse, scientists were quick to find an alternative explanation. Samples taken from the dead king’s corpse revealed that he had been riddled with the fungal spores of Aspergillus flavus.

“Most people breathe in Aspergillus spores every day without getting sick,” Tom Chiller, chief of the Mycotic Diseases Branch of the CDC, told Newsweek. “However, for people who have weakened immune systems, breathing in Aspergillus spores can cause an infection in the lungs or sinuses which can spread to other parts of the body.”

The resulting condition is called aspergillosis. “There are different types of aspergillosis,” Chiller said. “Some types are mild, but some of them are very serious and may be deadly.”

While Aspergillus fumigatus is the most common species of Aspergillus fungi in the U.S., Aspergillus flavus is more commonly found in Asia. As well as causing aspergillosis, this species has another nasty trick up its sleeve.

“A. flavus produces a toxin, flavitoxin, on stored grain,” Chiller said. “This toxin can be harmful or fatal to humans and animals and is a major source of crop spoilage.”

Among the treasures in Tutankhamun’s tomb were bags of bread and raw grain, which may have supported the growth of this fungus. But, if Aspergillus flavus was really responsible for the mummy’s curse, it would have had to lie waiting inside the boy king’s tomb for a very long time.

“Aspergillus are spore formers and, while preferring carbon rich substrates, [like] rotting logs, and damp conditions…they can survive in nutrient poor conditions with minimal water,” Michael Wise, a computer scientist from the University of Western Australia who studies microbial informatics, told Newsweek.

For most disease-causing organisms, killing their host is not beneficial as it prevents their transmission. However, if an organism was able to survive for long periods of time outside of their host, they could potentially evolve to be more lethal. This theory has become known as the sit-and-wait hypothesis.

In 2017, Wise and his team found genetic evidence that microbes with the potential to use this tactic tend to be more durable and more virulent than other species, providing support for the theory. The study was conducted in bacteria, but it’s likely that similar principles apply to fungi, like Aspergillus.

“The sit-and-wait tactic is beneficial any time a microbe is likely to be exposed to the environment, where it needs to persist until the next host encounter,” Wise said. “This is in contrast to obligate pathogens, like SARS-CoV2, which must be passed from host to host, and will perish if exposed to the environment.”

To survive through these long periods of waiting, the microbes must enter a vegetative state that persists until they are in contact with their hosts once more. For Aspergillus, this would be in the form of spores.

Aspergillus fungi are known to live on dead bodies and decaying matter and have been detected on other Ancient Egyptian mummies. Aspergillus poisoning also fits as a contributing factor to the deaths of at least three of the victims of the so-called mummy’s curse. Therefore, while it is impossible to know for sure, Aspergillus infection may be science’s answer to the curse of Tutankhamun.

“It is plausible,” Wise said. “[And] modern environmental metagenomics is getting to the point of being able to resolve the question.”