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- A pulmonary fungal infection caused by the dimorphic fungus, Coccidioides immitis, which is endemic to the southwestern deserts of the United States:
- Inhalation of air-borne fungal spores in the form of arthroconidia is the route of transmission.
- Rarely progresses to involve extrapulmonary sites (<1%): bone, CNS, endocrine/metabolic, musculoskeletal, nervous, pulmonary, skin, and exocrine systems
- Incubation period is 1 to 4 weeks after exposure.
- Pulmonary infection is the most common clinical manifestation; most commonly subacute; more than half of infections are subclinical (1).
- Synonym(s): desert rheumatism; cocci; valley fever
Affects patients of all ages, with no gender predilection
- In the United States: 150,000 cases estimated per year (0.5% extrapulmonary). Overall incidence is rising; 73% increase in African Americans, who also have a higher rate of invasive disease than Caucasians (2)
- Endemic in
- Southern Arizona
- Southern and Central California
- Southwestern New Mexico, West Texas
- Parts of Mexico, Central and South America
- Increased construction activities, such as home-building, especially in the southwestern United States, has likely resulted in increased aerosolization of fungal spores from soil, leading to increased exposure to and infection with C. immitis.
Can account for 17–29% of all community-acquired pneumonias in endemic areas (1)
Etiology and Pathophysiology
- C. immitis is a soil-dwelling fungus well-adapted to arid conditions. The organism can remain dormant in the soil for years.
- Liberated spores (arthroconidia) are inhaled when soil is disturbed. Upon inhalation, spores convert to spherules in the lung to cause clinical disease.
- Less commonly, spores are introduced through a wound.
- Certain groups are more prone to dissemination:
- Immunosuppressed patients: chemotherapy and/or immunosuppressive drugs for cancer or transplant patients, diabetes mellitus, HIV/AIDS, long-term steroid use, transplant patients, pregnancy
- Blacks and Filipinos
- Previously infected patients can experience relapse years later through cell-mediated immune deficiency.
- CNS involvement is more common in young white men.
- No person-to-person spread
- Lab cultures are highly contagious (inhalation); use caution when handling specimens.
- High-risk patients should avoid archaeologic digs, spelunking, or exposure to dust in endemic areas (this can be difficult to achieve due to construction, dust storms, etc.).