Still, the disease seems ideally suited to take advantage of Arizona's climate of the future. The Southwest is already the hottest, driest region in the country, and it is getting worse: The average temperature has increased about 1.5º Fahrenheit over the last century, compared to 1.3ºF for the rest of the mainland United States. The average annual Southwest temperature is projected to rise an additional 2.5ºF to 8ºF by the end of this century, according to federal estimates. The fungi's heat and drought tolerance allow it to live through conditions that kill other plants, Comrie said.
'Grow and blow'
The fungus also relies on moist winter, and that season is getting slightly wetter – ideal "grow and blow" conditions that researchers believe will make matters worse. Rain prompts fungal growth; heat lets it blow around months later.
The Valley Fever Center says most infections go unreported and estimates that the truer number of annual infections in the Southwest is closer to 150,000 cases. The United States has a "lion's share" of the total number of infections worldwide, Galgiani said, and 97 percent of all U.S. cases are in California and Arizona.
After a truncated 2009 season, Jackson bounced around for the next few years, splitting his time between major league and minor league teams. Jackson, 31, retired from baseball on April 14 after spending a few weeks in the minors this spring after the Baltimore Orioles cut him from their major league roster.
Jackson did not return several calls left with the team and on his cell phone, and his decline can't be directly blamed on Valley Fever.
Galgiani – who did not treat Jackson but followed his case – said Jackson had a mild form of the disease. But even the mild form can put the healthiest of people out of commission, he said. "I had one patient who couldn't get out of bed for months."
The Met's Davis, who lives off-season in Arizona, has bounced back well from his 2012 battle with Valley Fever and is starting at first base this year.
This article originally appeared at The Daily Climate, the climate change news source published by Environmental Health Sciences, a nonprofit media company.