The number of valley fever cases in Arizona surged in November, putting the state at a year-end total above 2016, the Arizona Department of Health Services said.
There were 926 cases reported in November, the highest monthly total since September 2015, The Arizona Republic reported Wednesday.
Officials aren't sure how to explain the November surge, said Cara Christ, the state's health care director.
The high volume of reports in November will likely put 2017's total over the 6,101 cases reported in 2016.
Officials believe 2017's total will remain under the 2015 total of 7,622.
Valley fever is a sometimes deadly respiratory illness caused by spores found in soil. It can cause flu-like symptoms such as fever, cough, fatigue, shortness of breath and rash.
Most cases occur in California and Arizona. Experts believe the disease is under-reported.
Part of the problem is that many doctors in Arizona's Maricopa County were trained in areas where the disease is rare, said Dr. John Galgiani, director of the University of Arizona's Valley Fever Center for Excellence.
A state health department study found that only a small percentage of people diagnosed with pneumonia are tested for valley fever, Galgiani said.
Doctors should always orders tests for valley fever for patients experiencing pneumonia, he said.
A new test for the disease by a Utah company promises to deliver results quicker.
While it can take a lab up to three weeks to complete the existing test, DxNA LLC can have the results within an hour, said David Taus, the company's CEO.
Michael Saubolle, a clinical microbiologist with Sonora Quest, expects the medical laboratory to begin offering the DxNA test in early to mid-2018.