California is seeing a spike in cases of Valley Fever and health officials are flummoxed as to the cause of the increase.

The California Department of Public Health reported Tuesday that there has been an overall increase in the number of cases of the virus being reported at local health departments, when compared to the same time period as last year.

Valley Fever, also known as coccidioidomycosis, is caused by the spore of a fungus that grows in soil in parts of California, Arizona and other areas of the southwestern United States. People get infected by breathing in spores present in dust that gets into the air when it is windy or when soil is disturbed, such as through digging during construction.

Most infected people will not show signs of illness. Those who do become ill with Valley Fever may have symptoms similar to other illnesses, including influenza or bacterial or viral pneumonia, so Valley Fever is not always recognized.

The flu-like symptoms can last for two weeks or more. While most people recover fully, some people are at risk for more severe disease or complications of Valley Fever such as pneumonia, infection of the brain, joints, bone, skin or other organs.

People with an increased risk for severe disease include those 60 years or older, pregnant women and people with diabetes or conditions that weaken their immune system. Additionally, African-Americans and Filipinos are at increased risk for severe disease, but the reason is unknown.

From Jan. 1 through Oct. 31, there were 5,121 provisional cases of Valley Fever reported in California. This is an increase of 1,294 provisional cases from the provisional 3,827 cases reported during that same time period in 2016.

In Stanislaus County, there has been 85 provisional reported cases, which is up from the 57 reported in 2016 and the 41 in 2015. Merced County has seen 84 provisional cases this year, up from 63 in 2016 and 67 in 2015.

Kern County has the highest rate of incidences in the state, with 1,855 provisional cases reported this year.

“With an increase in reported Valley Fever cases, it is important that people living, working, and travelling in California are aware of its symptoms, especially in the southern San Joaquin Valley and the Central Coast, where it is most common,” said CDPH Director and State Public Health Officer Dr. Karen Smith. “In these areas, anyone who develops flu-like symptoms, such as cough, fever, or difficulty breathing, lasting two weeks or more, should ask their health care provider about Valley Fever.”

The number of provisional cases provides a timely indicator of overall current activity, but the number of cases eventually confirmed is usually a lower number. Provisional cases include suspect, probable, and confirmed cases: suspect and probable cases may be confirmed later or excluded as official Valley Fever cases upon further investigation.

The number of Valley Fever cases varies from year to year, and by season. Cases can be more common in the late summer and fall. 

Anyone can get Valley Fever, even young and healthy people. People who live, work, or travel in areas with high rates of Valley Fever may be a higher risk of getting infected than others, especially if they: Participate in recreational activities where dirt and soil are disturbed; or work in jobs where dirt and soil are disturbed, including construction, farming, military work, and archaeology.

If you think you might have Valley Fever, visit your healthcare provider. Since Valley Fever symptoms are similar to those of other illnesses, your provider may order a blood test or other tests, such as a chest x-ray, to help diagnose Valley Fever. Treatment is usually not necessary for mild infections, which often get better on their own. All persons with symptoms, however, should see a healthcare provider who can determine if treatment is needed. If you are diagnosed with Valley Fever it is very important to follow instructions given by your healthcare provider about treatment, follow-up appointments, and testing.