Coccidioidomycosis (Valley Fever)
Coccidioidomycosis caused by the dimorphic pathogenic fungi Coccidioides immitis and Coccidioides posadasii.
Epidemiology and distribution
Coccidioides immitis and Coccidioides posadasii are endemic to the Western Hemisphere’s arid regions, especially in Southwestern United States and Central and South America. (1) The disease was first identified in Argentina and then in California, where from 1992 to 1995 there was a significant surge in cases in the southern San Joaquin Valley; hence, the commonly used name of San Joaquin Valley fever (also called Valley Fever). Currently, it is estimated that there are more than 150,000 yearly infections in the USA, and the numbers are significantly increasing each year. (2)
Risk factors
Coccidioidomycosis can occur in persons of any age, however it is most frequent in people over 60. Certain categories may be at a higher risk of developing the disease’s severe version, such as immunocompromised individuals, including pregnant women, people who have HIV, have had an organ transplant or are taking large doses of medications such as corticosteroids or TNF-inhibitors.
Symptoms
Clinical manifestations of coccidioidomycosis range from asymptomatic infection to lethal disease. The majority of Coccidioides encounters result in an asymptomatic (about 60%) or undetected (roughly 40%) respiratory illness. Around 1% of total infections spread, resulting in the most severe type of Coccidioidomycosis. By convention, Coccidioidomycosis that is not limited to pleural or pulmonary infection is considered disseminated. (3) Symptoms arise seven to twenty-one days after exposure.
The most common symptoms are cough, fever, shortness of breath, and chest discomfort. Classic signs include a headache, weight loss, and a rash. (3)
Diagnosis and treatment
Coccidioidomycosis is diagnosed using a mix of epidemiological, clinical, general laboratory, specific microbiological, serological, histological, and radiographic methods. Typical symptoms are similar to pneumonia or bronchitis and are overlapping with community-acquired pneumonia, making a definite diagnosis of Coccidioidomycosis difficult. Serologic tests, performed in conjunction with clinical symptoms and other laboratory tests, are the most commonly utilized diagnostic technique. Coccidioides spp. diagnostics include enzyme immunoassays
(EIA), immunodiffusion, and complement fixation (CF). (4) Although serology is the most commonly used method, a positive culture or cytopathological/histopathological identification of the organism in clinical specimens remains the gold standard for Coccidioidomycosis diagnosis. (4) In large reference laboratories, ultimate validation using in situ hybridization or PCR is frequent. (5) There are presently no antifungal medications with a specific indication for Coccidioidomycosis. The majority of treatments are based on observational research, anecdotes, and expert opinion. Fluconazole is commonly utilized as a first-line treatment for mild to moderate pneumonic disease and non-life-threatening disseminated disease (soft tissues, skin and small bones). (2)
References
1. Bays, D.J. and Thompson, G.R. (2021). Coccidioidomycosis. Infectious Disease Clinics of North America, 35(2), pp.453–469. doi:10.1016/j.idc.2021.03.010.
2. Johnson RH, Sharma R, Kuran R, Fong I, Heidari A. Coccidioidomycosis: a review. J Investig Med. 2021 Feb;69(2):316-323. doi: 10.1136/jim-2020-001655.
Erratum in: J Investig Med. 2021 Dec;69(8):1486. PMID: 33495302; PMCID: PMC7848065.
3. Akram SM, Koirala J. Coccidioidomycosis. [Updated 2022 May 2]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK448161/
4. Malo, J., Luraschi-Monjagatta, C., Wolk, D.M., Thompson, R., Hage, C.A. and Knox, K.S. (2014). Update on the Diagnosis of Pulmonary Coccidioidomycosis. Annals of the American Thoracic Society, 11(2), pp.243–253. doi:10.1513/annalsats.201308-286fr.
5. Binnicker MJ, Buckwalter SP, Eisberner JJ, Stewart RA, McCullough AE, Wohlfiel SL, Wengenack NL. Detection of Coccidioides species in clinical specimens by real-time PCR. J Clin Microbiol. 2007 Jan;45(1):173-8. doi: 10.1128/JCM.01776-06. Epub 2006 Nov 15. PMID: 17108077; PMCID: PMC1828991.