Valley Fever cases on the rise in California
August 11, 2017
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The number of reported cases of Valley Fever is increasing in the Central Valley, according to a report Friday from the federal Centers for Disease Control and Prevention.
Valley Fever is an infectious disease caused by breathing in “Coccidioides” spores that are found in the soils of the southern San Joaquin Valley and elsewhere in the Southwest.
Patients most often experience mild flu-like symptoms, but Valley Fever also can lead to severe pulmonary disease and to rare cases of diseases such as meningitis. Those at increased risk for severe disease include persons of African or Filipino descent, pregnant women, adults in older age groups, and persons with weakened immune systems.
The CDC says that in 2016, a large increase in Valley Fever cases was seen in California compared with previous years.
The reasons for the increased incidence of Valley Fever in California in 2016, particularly in the Central Valley and Central Coast regions, are not known, but climatic and environmental factors favorable to spore proliferation and airborne release might have contributed, including rainfall after several years of drought and soil disturbance resulting from construction, the CDC report says.
From 1995, when Valley Fever became an individually reportable disease in California, to 2009, annual incidence rates ranged from 1.9 to 8.4 cases per 100,000 in population, followed by a substantial increase to 11.9 per 100,000 in 2010 and a peak of 13.8 per 100,000 in 2011.
Annual rates decreased during 2012-2014, but increased in 2016 to 13.7 per 100,000, with 5,372 reported cases, the highest annual number of cases in California recorded to date.
Most cases last year were in residents of the Central Valley and Central Coast regions, with 42 percent (2,238 cases, or 251.7 per 100,000) reported from Kern County and 28 percent (1,515 cases, or 54.5 cases per 100,000) from six other counties -- Fresno, Kings, Madera, San Joaquin, San Luis Obispo, and Tulare.
From 2015 to 2016, the combined incidence from these seven counties increased 109 percent, from 48.9 per 100,000 (2015) to 102.3 (2016), while the rate in the remaining counties in California increased by 18 percent (from 3.8 to 4.5 per 100,000).
Other findings from the CDC report about the 2016 Valley Fever outbreak include:
• Incidence was highest among persons aged 40-59 years (18.8 per 100,000)
• However, the sharpest increases in incidence from 2015 to 2016 occurred in persons aged younger than 20 years of age: 134 percent) and those between 20 and 39 years (90 percent)
• Rates were higher among males (17.3 per 100,000) than among females (10.0).
Incidence rates by race and ethnicity were not calculated because these data were missing for approximately one third (32.7 percent) of reports.
To decrease the risk for infection, the CDC says, persons living, working, or traveling in areas where Valley Fever is endemic, especially those at increased risk for severe disease, should limit exposure to outdoor dust as much as possible, including staying inside and keeping windows and doors closed during windy weather and dusty conditions.
Previous outbreaks have occurred among persons working outdoors in areas where the spores are endemic, including construction workers.
Recommendations for reducing the risk for infection on construction worksites include using personal protective respiratory equipment, dust suppression, and worker education.