Two figures, one table omitted
Coccidioidomycosis is a systemic infection caused by inhalation of airborne
spores from Coccidioides immitis, a fungus found
in soil in the southwestern United States and in parts of Mexico and Central
and South America.1 Infection occurs usually
following activities or natural events that disrupt the soil, resulting in
aerosolization of the fungal arthrospores.2 Clinical
manifestations occur in 40% of infected persons and range from an influenza-like
illness (ILI) to severe pneumonia and, rarely, extrapulmonary disseminated
disease.3 Persons at higher risk for disseminated
disease include blacks, Filipinos, pregnant women in their third trimester,
and immunocompromised persons.4 During 2001,
the Arizona Department of Health Services (ADHS) reported a coccidioidomycosis
incidence of 43 cases per 100,000 population, representing an increase of
186% since 1995.3 To characterize this increase,
CDC analyzed data from the National Electronic Telecommunications System for
Surveillance (NETSS) and the Arizona Hospital Discharge Database (AHDD), and
environmental and climatic data, and conducted a cohort study of a random
sample of patients with coccidioidomycosis. This report summarizes the findings
of this investigation, which indicate that the recent Arizona coccidioidomycosis
epidemic is attributed to seasonal peaks in incidence that probably are related
to climate. Health-care providers in Arizona should be aware that peak periods
of coccidioidomycosis incidence occur during the winter and should consider
testing patients with ILI.
Coccidioidomycosis became a nationally reportable disease at the southwest
regional level through NETSS in 1995, at which time a case definition was
adopted that required laboratory confirmation.* During 1997, laboratory reporting
of coccidioidomycosis became mandatory in Arizona, after which a marked increase
was noted in the number of reported cases. However, incidence continued to
increase in subsequent years. NETSS data for 1998-2001 were analyzed to calculate
incidence by using U.S. Census 2000 data for denominators.
During 2001, a total of 2,203 cases were reported to ADHS (rate: 43
cases per 100,000 population), compared with 1,551 cases in 1998 (rate: 33).
Persons aged ≥65 years had the highest incidence (79 during 2001), although
incidence in all age groups increased. The youngest age groups experienced
the largest increase in incidence during the surveillance period: during 2001,
incidence of coccidioidomycosis among patients aged <20 years increased
121%, from approximately five in 1998 to 11 in 2001. Analysis by season demonstrated
peak periods of disease incidence during the winter months (November-February).
The baseline rate between peak periods was stable, indicating that the seasonal
periods were responsible for the overall annual increase in reported cases.
AHDD was reviewed to identify patients with a primary or secondary discharge
diagnosis of coccidioidomycosis (International Classification
of Diseases, Ninth Revision codes 114.0-114.3 and 114.5-114.9). Hospitalizations
caused by coccidioidomycosis increased substantially during the study period.
During 2001, a total of 598 persons were discharged with a primary or secondary
diagnosis of coccidioidomycosis, compared with 69 persons during 1998; 154
(26%) of the 598 hospitalized patients had disseminated coccidioidomycosis.
Persons aged ≥65 years comprised 34% of all hospitalized patients during
the study period and had the highest rate of hospitalization (29 per 100,000
population during 2001).
To explain peak periods and to further characterize the epidemic, CDC
conducted a cohort study of patients from NETSS who had coccidioidomycosis
to evaluate host factors, exposures, and outcomes. Patients reported with
coccidioidomycosis were divided into four groups based on inclusion in peak
or nonpeak periods and year of disease. Of 208 randomly selected persons contacted
by telephone, 196 (94%) completed a questionnaire (range per group: 43-56
persons). No statistically significant differences were found between groups
related to host risk factors or exposures that could explain the large peak
Geographic Information Systems (GIS) software was used to identify areas
of high incidence in Maricopa County, the most populous county in Arizona.
Locations of patients identified in NETSS and AHDD were plotted by postal
code by using Arc View v3.2, and incidence was calculated by using U.S. Census
2000 data. The highest incidence of coccidioidomycosis for both NETSS cases
and hospitalizations occurred in areas surrounding metropolitan Phoenix. These
areas have experienced substantial construction activity according to building
permit data provided by the Maricopa County Association of Governments. Seasonal
variations in construction activity approximated by building permits were
not significantly associated with cases.
Arizona has been experiencing dry weather conditions recently. Environmental
and climatic data were analyzed in relation to incidence of disease, and Poisson
regression was performed to construct a model that might predict seasonal
peaks. Many climatic variables were significantly associated with increased
incidence of disease, including drought indices (Palmer Z Index and Palmer
Drought Severity Index), wind velocity, mean temperature, dust (measured by
concentration of suspended particulate matter ≤10 microns), and rain.
Poisson regression analysis indicated a high correlation (R-squared
= 0.75) between incidence of disease and (1) cumulative rain during the preceding
7 months, (2) the average temperature during the preceding 3 months, (3) dust
during the preceding month, and (4) the amount of rain during the preceding
2 months in proportion to the preceding 7 months. The projected cases based
on the model were compared with the actual cases in Maricopa County. The model
accurately mirrored peak seasonal periods during 1998-1999, in particular
the large peak beginning in November 2001. In addition, the model accurately
described the absence of a seasonal peak during winter 2000-01.
K Komatsu, V Vaz, C McRill, T Colman, Arizona Dept of Health Svcs; A
Comrie, Univ of Arizona Dept of Geography, Tucson. K Sigel, T Clark, M Phelan,
R Hajjeh, Div of Bacterial and Mycotic Diseases, National Center for Infectious
Diseases; B Park, MD, EIS Officer, CDC.
Coccidioidomycosis is the fourth most common infectious disease reported
to ADHS; only gonorrhea, chlamydia, and chronic hepatitis C are more frequent
(ADHS, unpublished data, 2002). The findings in this report indicate that
the incidence of coccidioidomycosis in Arizona has increased substantially
since 1998, affecting all age groups. In addition, hospitalizations for coccidioidomycosis
have increased, indicating an increase in the numbers of persons with severe
Although seasonality of coccidioidomycosis in Arizona has been suggested
previously, this study is the first to confirm the pattern.5,6 In
addition, this study documents peak incidence periods during November-February;
improved timeliness and completeness of reporting because of mandatory laboratory
reporting since 1997 might have helped reveal the seasonal pattern. Seasonal
fluctuations could not be explained by differences in the prevalence of the
various host risk factors or exposures but were significantly associated with
climatic and environmental factors. A climate model incorporating some of
these factors recreated the seasonal outbreaks in Maricopa county and predicted
that large outbreak seasons might occur during winter seasons following prolonged
drought periods, especially in conjunction with hot and dusty conditions.
These conditions, which might facilitate aerosolization of arthrospores, have
been described in studies of coccidioidomycosis epidemics in California.7 Dry and dusty conditions continue in Arizona, suggesting
that another large peak season might occur this winter. Preliminary data for
2002 indicate that the number of total cases already exceeds 3,000, considerably
surpassing 2001 levels (ADHS, unpublished data, 2002).
Although coccidioidomycosis is not readily preventable, a better understanding
of its epidemiology can assist in developing more effective prevention and
education strategies and help with earlier diagnosis and appropriate medical
management. Health-care providers should consider testing for coccidioidomycosis
in any patient who has moved or traveled recently to Arizona and who has ILI,
especially during the winter months. Dust reduction measures, such as paving
roads or wetting soil at construction sites, are currently in place and might
be useful in preventing further cases. Persons at risk for severe disease
should avoid activities that might increase their exposure to dust. These
persons might benefit from development of a vaccine that confers long-term
*The laboratory criteria for diagnosis are cultural, histopathologic,
or molecular evidence of the presence of Coccidioides spp; a positive serologic test for coccidioidal antibodies in serum or
cerebrospinal fluid by (1) detection of coccidioidal IgM by immunodiffusion,
enzyme immunoassay (EIA) latex agglutination, or tube precipitin or (2) detection
of rising titer of coccidioidal IgM by immunodiffusion, EIA, or complement
fixation; or a coccidioidal skin test conversion from negative to positive
after the onset of clinical signs and symptoms.
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