“We made projections out to the end of the 21st century, and our model predicts that Valley fever will travel farther north throughout the western United States, especially in the rain shadow of the Rocky Mountains and throughout the Great Plains, and by that time, much of the western U.S. will be considered endemic,” says the study’s lead author, Morgan Gorris, who earned a Ph.D. in Earth system science at UCI last month.
Recent reporting about climate change data and the projected increase of Valley Fever has people wondering how much worse the epidemic can get. I went directly to the source article published by the American Geophysical Union. The study tested to see how the endemic areas of Valley Fever might expand near the end of the century.
“The range of Valley fever is going to increase substantially,” said lead author Morgan Gorris, a former UCI Ph.D. student in Earth system science who was awarded her doctorate in August. “We made projections out to the end of the 21st century, and our model predicts that Valley fever will travel farther north throughout the western United States, especially in the rain shadow of the Rocky Mountains and throughout the Great Plains, and by that time, much of the western U.S. will be considered endemic.”
By matching temperature and rainfall from known Valley Fever endemic areas with temperature and rainfall projected to change elsewhere, this study examined previously published climate change models. The following graphic uses this data and projects how researchers believe Valley Fever’s endemic areas might expand by 2095, reaching out to Idaho, Montana, Nebraska, South Dakota, North Dakota and Wyoming.
Should these projections be accurate, Valley Fever research will be even more vital to national security and public health.
As always, a good article will leave us with more questions to investigate in the future.
How is the spread of Valley Fever expected to happen?
The study does not go into depth on exactly how the spores would spread. Instead it focused on finding areas with annual rainfall and temperature data that is now known to support the growth of Valley Fever and then finding places with climates that are expected to match those characteristics as time goes on.
There was a brief mention that spores could be blown for miles and that the possibility of animal migration to bring the spores to new areas (as first suggested in David Filip’s interview with the CDC’s Dr. Tom Chiller) but these were not the article’s focus. However, given the discovery of endemic areas in Oregon and Washington, it is perfectly reasonable to suspect that if a place can support the growth of Valley Fever, it ultimately will.
Lighter and darker colors indicate places of less or more severe Valley Fever risk, so if wind and atmospheric conditions can blow the spores for miles at a time, why are some of the areas uneven in risk on the chart?
Since temperature, rainfall, elevation, soil composition, and other factors may change how hospitable an area can be to Valley Fever, it is reasonable to expect some jagged changes on the projected map and not a perfectly smooth gradient.
Why won’t Valley Fever spread across the entire country by 2095?
The model found that projected rainfall would still be too strong in many areas for Valley Fever’s spores to take hold in some places. This included the Pacific Northwest’s coasts and the Eastern half of the continent.
Are the climate models accurate?
Several different models were used. Had this projection been done a decade earlier, it could have independently predicted the endemic areas that had been discovered in Washington state. With that in mind this data should be taken seriously for other predictions. However, the models’ predictive power in the future can only be known in time.
Bell B. UCI scientists project northward expansion of Valley fever by end of 21st century. UCI News. September 16, 2019. https://news.uci.edu/2019/09/16/uci-scientists-project-northward-expansion-of-valley-fever-by-end-of-21st-century/
Gorris ME, Treseder KK, Zender CS, Randerson JT. Expansion of coccidioidomycosis endemic regions in the United States in response to climate change. GeoHealth. 30 Aug 2019.