(CN) – Scientists who have taken on the role of detectives to determine the origin of a deadly fungal disease affecting people and wildlife in the Pacific Northwest announced Tuesday they may have finally found the answer.
In a paper published in the journal mBio, researchers revealed that the mysterious outbreak of the fungus Cryptococcus gattii that resulted in several hundred cases of infection in North America was likely due to the Great Alaskan Earthquake of 1964 and the subsequent tsunamis it caused.
The outbreak, which has been ongoing since 1999, baffled scientists how it arrived at the Pacific Northwest as the C. gattii fungus was normally only found in parts of Brazil, South America and around Australia. The study authors suggest that as shipping increased after the opening of the Panama Canal in 1914, ships from South America brought the fungus with them to the north.
Following the Great Alaskan Earthquake of 1964, the researchers believe the resulting tsunamis washed the fungus ashore where it began to spread among the coastal forest area. Scientists said they believe the fungus evolved to the point where it could infect humans to survive.
"The big new idea here is that tsunamis may be a significant mechanism by which pathogens spread from oceans and estuarial rivers onto land and then eventually to wildlife and humans," said Arturo Casadevall, microbiologist and co-author of the study. "If this hypothesis is correct, then we may eventually see similar outbreaks of C. gattii, or similar fungi, in areas inundated by the 2004 Indonesian tsunami and 2011 Japanese tsunami."
Since 1999, the U.S. Centers for Disease Control and Prevention reported over 300 infections in the Pacific Northwest and Canada. Before then, infections had only been reported in Papua New Guinea, South America and Australia.
The fungal disease primarily infects the central nervous system or lungs and can create a number of symptoms depending on the infection site. An infection in the lungs can bring about pneumonia-like symptoms, including chest pain, fever and coughing. If the infection spreads to the brain, it can also cause headaches, neck pain, nausea and behavioral changes. The fungus has a mortality rate of 13%-33%, depending on patient care.
Evidence of the fungus has been found in trees and the soil of coastal areas of Washington state, Oregon and British Columbia. Using scientific detective work, the scientists in the study analyzed the DNA structure of the fungus found in the Pacific Northwest and determined it matched fungus DNA found in Brazil 60 to 100 years ago, aligned with the opening of the Panama Canal.
While researchers were certain that the fungus was carried by South American ships, it still didn’t explain how so much of it was colonizing the Pacific Northwest coastline. That’s when the scientists hit upon the idea of the earthquake.
The Great Alaskan Earthquake of 1964, a 9.2 magnitude quake that remains the largest one recorded in the northern hemisphere, was responsible for spawning several tsunamis throughout the North Pacific Ocean. Even with this conjecture, scientists still had to question why infections only began appearing in North America after more than three decades.
Casadevall said it’s likely the fungus began to evolve as it moved into its new environment, creating defenses that allows it survive attacks from amoebas and subsequently allow it to infect humans as well.
"We propose that C. gattii may have lost much of its human-infecting capacity when it was living in seawater, but then when it got to land, amoebas and other soil organisms worked on it for three decades or so until new C. gattii variants arose that were more pathogenic to animals and people," Casadevall said.
The scientists said they will continue to test their hypothesis by comparing samples of the fungus in the Pacific Northwest to samples found in other parts of the world to determine if the same subtypes have made their way around the globe.
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