Coccidioidomycosis (Valley Fever)

Coccidioidomycosis is an infection caused by breathing in the spores of a fungus Coccidioides immitis found in soil in desert regions of the southwestern U.S., Mexico, and Central and South America. Sometimes called Valley Fever or Desert Fever because of its prevalence in farming valleys, these fungi resist drying and easily become airborne. It usually affects the lungs but can spread and affect many organs.

The disease can have an acute, chronic, or disseminated form. Acute pulmonary coccidioidomycosis is almost always mild, with few or no symptoms, and resolves without treatment. The incubation period is 10 to 30 days and the incidence about 1 out of 100,000 people.

Chronic pulmonary coccidioidomycosis can develop 20 or more years after initial infection which may not have been recognized, diagnosed, or treated. Infections (lung abscesses) can form and rupture releasing pus (empyema) between the lungs and ribs (pleural space). The incidence of chronic disease is also about 1 out of 100,000 people.

In disseminated disease, extension of infection to the bones, lungs, liver, meninges, brain, skin, heart, and pericardium (sac around the heart) may take place. Meningitis occurs in 30 to 50% of cases of disseminated disease. The course of the disease may be rapid for immunosuppressed patients.

When inhaled, as few as 10 surviving spores can cause infection and mature as quickly as 48-72 hours into an active fungal state. Although coccidioidomycosis is not contagious, lab personnel who handle specimens must take precautions to avoid contracting the illness.

Following inhalation and maturation of the cocci, humoral immunity predictably begins with immunoglobulin M (IgM), then IgG. Cellular immunity, particularly T-cells, becomes a key factor in determining recovery from coccidioidomycosis. A respiratory infection ensues.

The majority of patients recover from the respiratory infection with no or minimal consequences. Some develop complications in the lungs, such as tissue death or abscesses. Persistent pulmonary disease may manifest as persistent bronchitis and pneumonia. A subset of patients will develop infection outside the lungs: the infection spreads through blood either during the primary infection or as a reactivation from a chronic pulmonary site.

Areas affected outside of the lungs may include blood cell generating tissues, skin, kidneys, bones, the central nervous system and heart muscle. Disseminated disease can involve nearly every organ and can be especially dangerous in the immune compromised host. More often, in chronic cases, the disease progresses slowly.

Incidence and Prevalence

Coccidioidomycosis affects an estimated 100,000 people each year in the US. Coccidioidomycosis is endemic in the western hemisphere from California to Argentina. Coccidioidomycosis is also being recognized outside these areas as travelers pass through. Former residents of endemic areas suffer reactivation, and natural disasters such as earthquakes and dust storms create new epidemics.

Risk of infection is greatest on windy days when the soil is dry or when the soil is disturbed by activity. An example of such infectivity was noted following a large California dust storm after which 15 counties reported a tenfold or more increase in cases of coccidioidomycosis.

Areas outside of the US with a higher risk are characterized by semiarid climates with hot summers and alkaline soil include northern Mexico and Central and South America.

About 40% of those infected develop symptomatic disease, usually pulmonary. About 90% will resolve their pulmonary maladies without lasting consequences. Some 10% of patients will go on to harbor pulmonary lesions and nodules and about 1% develop disseminated disease.

Diseases and conditions that alter immune responses also predispose those affected to dissemination and serious disease. Pregnant women are at special risk for disseminated coccidioidomycosis.

Filipinos have the highest risk of dissemination, about 10-170 times the risk of whites. Blacks and Hispanics also have a higher risk of dissemination than whites. Blacks have a 5 times higher risk of developing meningitis than whites; Filipinos have a 10 times higher risk of developing meningitis than whites. Mortality rate is 5 times greater for blacks than for whites. The incidence is equal in males and females and persons of any age may be affected. In disseminated disease, the mortality rates in newborns and infants are much higher than those in children, adolescents and adults.

Coccidioidomycosis usually develops 1-4 weeks following exposure. About 60% of infections cause no symptoms and are only recognized by a positive coccidioidin skin test. In the remaining 40% symptoms range from mild to severe. Although the symptoms are very nonspecific, a level of suspicion should be maintained for those who live in or have traveled to endemic areas or have persistent symptoms. Skin tests, blood tests, and sputum cultures can be used for the diagnosis.

The results of medical therapies for coccidioidomycosis are unpredictable. Antifungal therapy for coccidioidomycosis often is less certain than for other fungal diseases. Fortunately, only about 5% of patients require therapy. Common drugs used include Amphotericin B, Diflucan, and Nizoral.


Signs, symptoms & indicators of Coccidioidomycosis (Valley Fever)

Lab Values - Common  

Rapid pulse rate

Symptoms - Cardiovascular  

(Possibly) enlarged spleen

Symptoms - Food - General  

Weak appetite

Symptoms - General  

Fatigue on light exertion

Symptoms - Glandular  

Swollen inguinal nodes


(Frequent) cervical node swelling


(Frequent) painful cervical nodes


(History of) swollen axillary nodes


(History of) painful axillary nodes


(Often) painful inguinal nodes

Symptoms - Metabolic  

Having a high/having a slight/having a moderate fever


Occassional/frequent 'chills' or having chills from an illness


Unexplained high/mild unexplained/moderate unexplained fevers or unexplained fevers that hit hard

Symptoms - Mind - General  

Periods of confusion/disorientation

Symptoms - Muscular  

Tender muscles

One third of patients with disseminated coccidioidomycosis have musculoskeletal involvement.

Symptoms - Respiratory  

Breathing pain


Chronic/recent nonproductive cough


Chest pain when breathing


Air hunger


(Frequent) sore throats

Symptoms - Skeletal  

Joint pain/swelling/stiffness

Symptoms - Skin - Conditions  


Conditions that suggest Coccidioidomycosis (Valley Fever)



Symptoms - Immune System  

(Disseminated) coccidioidomycosis

Counter Indicators
Symptoms - Immune System  

Absence of coccidioidomycosis

Risk factors for Coccidioidomycosis (Valley Fever)

The Immune System  

AIDS / Risk

The depressed cellular immunity seen in HIV infection increases the risk of coccidioidomycosis. Individuals with AIDS are at high risk not only for pulmonary coccidioidomycosis but for the disseminated form and cutaneous form of the disease.

Personal Background  

African ethnicity

Dark-skinned people and people with a compromised immune system tend to have more serious infections.

Symptoms - Immune System  

History of coccidioidomycosis

Symptoms - Metabolic  

Recent unexplained weight loss

Symptoms - Muscular  

History of tender muscles

One third of patients with disseminated coccidioidomycosis have musculoskeletal involvement.

Symptoms - Respiratory  

History of breathing pain

Coccidioidomycosis (Valley Fever) can lead to




Weak or unproven link
Strong or generally accepted link
Proven definite or direct link
Very strongly or absolutely counter-indicative



An illness or symptom of sudden onset, which generally has a short duration.


Usually Chronic illness: Illness extending over a long period of time.


Pertaining to the lungs.


Pus located in a body cavity.

Humoral Immunity

This refers to immunity to infection created by proteins termed antibodies, often referred to as "B" cells.

Cellular immunity

A branch of the immune system which involves direct attack by immune cells often called "T" cells. Antibodies play less of a role.


T cells are lymphocytes that are produced in the bone marrow and mature in the thymus. T cells are responsible for mediating the second branch of the immune system called "cellular immune response." T cells can live for months to years. This lymphocyte population is defined by the presence of a rearranged T-cell receptor.


Inflammation of the mucous membrane of the bronchial tubes, frequently accompanied by cough, hypersecretion of mucus, and expectoration of sputum. Acute bronchitis is usually caused by an infectious agent and of short duration. Chronic bronchitis, generally the result of smoking, may also be known as Chronic Obstructive Pulmonary Disease (COPD) or Emphysema.

Nervous System

A system in the body that is comprised of the brain, spinal cord, nerves, ganglia and parts of the receptor organs that receive and interpret stimuli and transmit impulses to effector organs.


Used to refer to a disease that constantly occurs in any particular geographical region.




Abbreviation for human immunodeficiency virus, a retrovirus associated with onset of advanced immunodeficiency syndrome (AIDS).

Immune System

A complex that protects the body from disease organisms and other foreign bodies. The system includes the humoral immune response and the cell-mediated response. The immune system also protects the body from invasion by making local barriers and inflammation.

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