Updated June 4, 2024
NCCID Disease Debriefs provide Canadian public health practitioners and clinicians with up-to-date reviews of essential information on prominent infectious diseases for Canadian public health practice. While not a formal literature review, information is gathered from key sources including the Public Health Agency of Canada (PHAC), the USA Centers for Disease Control and Prevention (CDC), the World Health Organization (WHO) and peer-reviewed literature.
This disease debrief was prepared by Robert Sager. Questions, comments, and suggestions regarding this disease brief are most welcome and can be sent to nccid@manitoba.ca
What are Disease Debriefs? To find out more about how information is collected, see our page dedicated to the Disease Debriefs.
Questions Addressed in this debrief:
- What are important characteristics of Valley fever?
- What is the current risk for Canadians from Valley fever?
- What is the prevalence of Valley fever in Canada?
- What measures should be taken for a suspected Valley fever case or contact?
What are important characteristics of Valley fever?
Characteristics and Causes
Valley fever (also known as coccidioidomycosis) is a lung infection caused by two species of the fungus Coccidioides. The fungus is found in soils in certain hot, dry climates. When the soil is disrupted by wind or outdoor activities (farming, construction, landscaping, etc.), the fungus releases spores into the air that are too small to be visible by the human eye. If a person inhales these spores, they are at risk of contracting Valley fever. In extremely rare occasions, the fungal spores can enter the body through broken skin (cuts, scrapes, wounds, splinters, etc.).
The Coccidioides fungus can be found in semiarid soils of the Pacific Northwest and Southwestern United States, Mexico, Central America, and South America. Although the C. immitis speciesis found typically in California and the C. posadasii species is found in other regions, climate change is expanding the geographic range of Valley fever as temperatures warm and precipitation patterns change. The majority of infections are asymptomatic; symptomatic individuals may develop acute pneumonia or Valley fever. In rare cases, Valley fever can cause severe, long-term infections in people who have a weakened immune system, are pregnant, are diabetic, or are aged 60 and older. Hosts of Valley fever include humans, most mammals, and some reptiles.
Pathogen Safety Data Sheets – Coccidioides – Government of Canada
Coccidioidomycosis – Causes of Coccidioidomycosis – Government of Canada
Symptoms
The time between exposure to the fungus and when symptoms develop ranges from 1 to 3 weeks and symptoms of Valley fever can last weeks to months. 60% of people infected with Valley fever are asymptomatic, while most others will experience mild symptoms. If an infected person has a normal immune response, and apart from complications, Valley fever will generally resolve without treatment. Symptoms of Valley fever can include:
- Fatigue or tiredness
- Fever
- Cough
- Shortness of breath
- Night sweats
- Headache
- Muscle aches or joint pain
- Red, spotty rash on upper body or legs
Coccidioidomycosis – Symptoms of Coccidioidomycosis – Government of Canada
Pathogen Safety Data Sheets – Coccidioides – Government of Canada
Valley Fever – Symptoms of Valley Fever – Centers for Disease Control and Prevention
Health Information and Tools – Valley Fever – Government of Alberta and Alberta Health Services
Severity and Complications
Between 5-10% of people who contract Valley fever will develop a severe, chronic form called pulmonary coccidioidomycosis. This can occur months to years after first being exposed to the fungus. It is characterized by pneumonia, pleural effusion, and hilar lymphadenopathy; cavities can also develop in the infected lungs. Less than 1% of Valley fever infections spread to other parts of the body. When they do, infections can include the skin, bones, joints, and nervous system (brain and spinal cord). The latter can lead to meningitis, a serious complication, which occurs in 30-50% of disseminated infections.People who have a weakened immune system, are pregnant, or are diabetic are at highest risk of developing pulmonary coccidioidomycosis.
Coccidioidomycosis – Symptoms of Coccidioidomycosis – Government of Canada
Pathogen Safety Data Sheets – Coccidioides – Government of Canada
Health Information and Tools – Valley Fever – Government of Alberta and Alberta Health Services
Epidemiology
General:
The fungus, Coccidioides, is primarily found in hot, dry climates in the dust and soil of:
- Pacific Northwest and Southwestern United States (Arizona, California, Nevada, New Mexico, Texas Utah, and south-central Washington State)
- Mexico
- Central America
- South America
Anyone who lives in or travels to these locations can get Valley fever. However, the geographic range of the fungus may expand to other areas because of climate change. While most cases of Valley fever are not associated with outbreaks, cases can be linked to a common source: among military trainees, archeological workers, farm workers, or during earthquakes and dust storms. The CDC reported 20,003 cases of Valley fever in 2019, with the majority in California and Arizona. From 1999 to 2019, there were on average approximately 200 coccidioidomycosis-associated deaths each year. While Valley fever can affect people of all ages, race, and sex, at-risk populations for severe infections include adults aged 60 and older, pregnant women, people with weakened immune systems, and people with diabetes.
Estimated Rates and Trends – Coccidioidomycosis – Centers for Disease Control and Prevention
Reducing Risk for Valley Fever – Coccidioidomycosis – Centers for Disease Control and Prevention
Clinical and Laboratory Diagnosis:
If symptoms, patient activity history, and patient travel history suggest possible infection, diagnosis can be made with a blood test to check for Coccidioides antibodies or antigens. A doctor may also order a sputum smear or culture to check a sample of discharged saliva or mucus for the presence of Coccidioides. Finally, a biopsy may be performed by removing a small amount of tissue from the body to test for signs of Coccidioides. Imaging tests such as chest x-rays or CT scans of a person’s lungs can check for pneumonia; however, due to correlated symptoms, it is difficult to make a specific diagnosis of Valley fever as opposed to other lung infections.
Testing for Valley Fever – Coccidioidomycosis – Centers for Disease Control and Prevention
Diagnosis – Valley fever – Mayo Clinic
Transmission
Valley fever cannot be spread between person to person or between people and animals.
Pathogen Safety Data Sheets – Coccidioides – Government of Canada
Prevention and Control
It may not be possible to completely avoid exposure to the fungus that causes coccidioidomycosis in environments where it is common. People who have weakened immune systems should consider avoiding dusty places, and activities that involve disrupting soil in these areas. Recommended prevention strategies include:
- wearing a protective face mask
- avoiding areas with a lot of dust, such as construction or excavation sites
- avoiding activities that involve exposure to dirt or dust, including yard work, gardening, and landscaping.
- applying air filtration measures indoors.
- covering and cleaning exposed skin injuries
Reducing Risk for Valley Fever – Coccidioidomycosis – Centers for Disease Control and Prevention
Vaccines
There is no vaccine to prevent Valley fever.
Reducing Risk for Valley Fever – Coccidioidomycosis – Centers for Disease Control and Prevention
Treatment
Illness caused by coccidioidomycosis can be minimized by early recognition and appropriate treatment of the disease. Awareness of the disease by both the public and health care providers is key to early diagnosis. Most Valley fever infections will resolve without treatment. For severe cases where the infection has or may spread to other parts of the body or the patient experiences excessive morbidity, doctors may prescribe antifungal medicines. Oral antifungal medicine includes fluconazole or itraconazole, and intravenous antifungal medicine include amphotericin. The type of drug and length of treatment depends on the sites of infection and clinical response. To ensure an effective recovery, it is important for people with Valley fever to follow-up with their doctor. Chest x-rays and blood tests after several months can be used to monitor treatment progress. Prior to infection, people that have been exposed to Coccidioides can be given 400 mg itraconazole or fluconazole daily for 6 weeks as a precaution. For most infections, a single bout of Valley fever results in lifelong immunity. Rarely, the disease can be reactivated, or a person can be reinfected if their immune system is significantly weakened.
Pathogen Safety Data Sheets – Coccidioides – Government of Canada
Treatment – Valley fever – Mayo Clinic
What is happening with current outbreaks?
Valley fever is not endemic to Canada. Cases are very rare; all cases diagnosed in Canada have been acquired during travel to coccidioidomycosis-endemic areas such as the Pacific Northwest and Southwestern United States, Mexico, Central America, and South America.
Coccidioidomycosis – Causes of Coccidioidomycosis – Government of Canada
What is the current risk for Canadians?
Overall risk to Canadians is extremely low, but risk is higher for individuals living or travelling in areas where the Coccidioides fungi are endemic. Incidence ofValleyfever in western Canadians is higher, as they are more likely to travel to the southwestern United States.
Coccidioidomycosis – Risks of Coccidioidomycosis – Government of Canada
What measures should be taken for a suspected case or contact?
Valley fever (coccidioidomycosis) is not a reportable disease in any Canadian province or territory. There is no protocol for suspected cases in Canada.