El Nino, Valley Fever, and Arizona

Feb 26, 2016 | Tessa Runels, Cheryl Lang, Colleen Nguyen | Outbreak News

Valley Fever is a disease that is becoming all too common in parts of the Southwest United States such as Arizona and California. This disease, which is gaining notoriety among residents and visitors to these states, is spread through the dust that is a hallmark of this region. The disease-causing spores that are spread via dust are highly sensitive to slight changes in the weather (1,2). It is predicted that this year’s unique weather patterns caused by El Niño will greatly influence the number of Valley Fever cases diagnosed in the area.


What is Valley Fever?

Valley Fever is also sometimes known as coccidioidal granuloma, desert fever, desert rheumatism and San Joaquin Valley Fever (1). Valley Fever is a caused by the spores of fungus Coccidioides, which can be found in the soil and dust of desert regions across North, Central, and South America (1,2). Within the United States, this fungus has been found in southwestern states such as Arizona, California, Nevada, New Mexico, Texas, and Utah (3,4). Recently, the species of Coccidioides that causes Valley Fever have even been found as far north as Washington State (5,6).


Symptoms and Treatment

The most common way for someone to contract Valley Fever is through the inhalation of airborne Coccidioides spores (3). Although it is possible for people to become infected in other ways, these routes of exposure are extremely rare. Some examples of alternative routes of transmission include: infection following transplant of an infected organ, inhalation of spores from an infected wound, and direct contact with objects that have been contaminated with Coccidioides spores (3). Valley Fever often manifests itself with mild symptoms such as general malaise, often resembling those of the flu (7). However, approximately 40 percent of people who are infected do not show any symptoms (8). In rare cases, if the initial infection fails to resolve on its own or is not treated, it can progress to chronic or disseminated Valley Fever (7,8).


Because severity of infection varies widely among individuals, treatment is not always indicated. Patients who exhibit early signs of infection often do not need any antifungal therapy since the infection tends to resolve on its own (4). Conversely, patients who show signs of severe pneumonia soon after infection tend to require antifungal therapy (4). Those who develop chronic pulmonary or disseminated disease, especially those who are immunocompromised, can require prolonged and potentially lifelong antifungal therapy (4).


Who is at Risk?

The CDC notes that the following risk factors put an individual at potentially increased risk of Valley Fever: over the age of 60, immunocompromised, pregnant, diabetic or of Black or Filipino ethnicity may be at higher risk of contracting the more severe forms of Valley Fever (7). Those who live in, or are traveling to, the areas where the fungus is commonly found are also at increased risk of infection. Since 1998, there has been a steady increase in the number of cases reported, but this may be a result of environmental factors, an increase in the number of susceptible people exposed or an artifactual change in the reporting mechanisms (6).


Valley Fever with Respect to El Niño?

El Niño Southern Oscillation is a cyclical climate anomaly that occurs when there are above-average surface temperatures in certain parts of the Pacific Ocean (9). This increase in sea surface water temperatures then can influence worldwide rainfall totals, wind strength, and wind direction. During an El Niño season, the winds that normally blow from east to west along the equator weaken and can sometimes even change direction (9). This change in weather patterns can affect the rates of certain diseases, such as Valley Fever. It has been suggested that an increase in rainfall in the wintertime or in the off-season is directly proportional to an increased number of spores in the environment during the dry season—the period at which most people become infected due to the dustier and drier conditions (10, 11). Given the spores sensitivity to climate change, both weather and health experts have expressed heightened interest in documenting rates of Valley Fever with regards to this year’s particularly strong El Niño. In states such as Arizona, there is increasing concern surrounding the potential spike in cases since 65% of nationally reported Valley Fever cases have occurred within the state (12,11).

As of right now, there is no telling how El Niño will affect the incidence of Valley Fever and the dispersion of the disease-causing spores. The number of cases of Valley Fever could very well change as a result of these disturbances in atmospheric circulation. It is unclear whether heightened clinical awareness, changes in reporting, or a true increase in the number of cases will be observed. However, it is apparent that additional research on this topic is necessary to understand just how Valley Fever is affected by seasonal weather changes (12).




1. Ohio Department of Public Health. (2015). Coccidioidomycosis. Retrieved from http://www.odh.ohio.gov/pdf/idcm/coccid.pdf

2. Sharpton TJ et al., Comparative genomic analyses of the human fungal pathogens Coccidioides and their relatives. Genome Res, 2009 Aug 28;19(10):1722-31.

3. Centers for Disease Control and Prevention. (2016). Sources of valley fever (Coccidioidomycosis). Retrieved from http://www.cdc.gov/fungal/diseases/coccidioidomycosis/causes.html#one

4.  Galgiani, J. N., Ampel, N. M., Blair, J. E., Catanzaro, A., Johnson, R. H., Stevens, D. A., & Williams, P. L. (2005). Https://cid.oxfordjournals.org/content/41/9/1217.full#cited-by. Oxford Journal, 41(9), 1217-1223. Retrieved from https://cid.oxfordjournals.org/content/41/9/1217.full#cited-by.

5. Marsden-Haug N, Goldoft M, Ralston C, Limaye AP, Chua J, Hill H, et al. Coccidioidomycosis acquired in Washington State. Clin Infect Dis. 2013 Mar;56(6):847-50.)

6. Centers for Disease Control and Prevention. (n.d.) Valley fever and the expanding geographical range of Coccidioides. Retrieved from http://www.cdc.gov/fungal/pdf/valley-fever-expanding-cocci-508c.pdf

7.  Centers for Disease Control and Prevention. (2014). Ten things to know about valley fever. Retrieved from http://www.cdc.gov/features/valley-fever-10-things/

8.  Valley fever. (n.d.). Retrieved from http://www.mayoclinic.org/diseases-conditions/valley-fever/basics/sympto...

9. L'Heuruex, M. (n.d.). What is the El Niño–southern oscillation (ENSO) in a nutshell? NOAA Climate.gov. Retrieved from https://www.climate.gov/news-features/blogs/enso/what-el-niño–souther...

10.  Hauser, A. (n.d.). Is It Valley Fever? 8 symptoms you should know. Retrieved February 18, 2016, from https://weather.com/health/news/valley-fever-symptoms

11. Tamerius, J. D., & Comrie, A. C. (2011). Coccidioidomycosis incidence in Arizona predicted by seasonal precipitation. PLoS ONE, 6(6). Retrieved from http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0021009

12. Marroquin, A. (n.d.). El Niño could cause spike in Arizona valley fever cases. Retrieved February 18, 2016, from http://www.azcentral.com/story/news/local/arizona/2016/01/29/httpcronkit...

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