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Background While increasing age is a known risk factor for neuroinvasive West Nile virus (WNV) disease, little is known about risk factors for West Nile fever (WNF). In 2003, United States blood centers identified WN (West Nile) viremic donors using nucleic acid-amplification tests (NATs), making it possible to prospectively determine risk factors for WNF. We report the characteristics of WN viremia among donors at Colorado's largest blood center and risk factors for WNF in viremic donors.Methods Prospective public health surveillance was conducted in WN viremic donors. NAT-reactive donors who developed WNV-specific IgM antibody were considered viremic donors. Demographic data were abstracted from blood center records for all viremic donors aged ≥18 years. Standardized telephone questionnaires were administered a median of 39 days following donation. Donors reporting fever and headache within seven days following donation were considered West Nile fever (WNF) cases.Results Of 66,771 donations screened from July 1–October 31, 146 (0.22) were from viremic donors (1457 donations). Of 135 surveyed donors, 81 (60) were male. The median age was 49 years (range 18–78). Forty-one (30) donors developed WNF; of these, 12 (29) visited a physician. Other reported symptoms included body aches (98), eye pain (63), and skin rash (61). The risk of WNF was inversely correlated with age (odds ratio 0.95 for every 1-year increase in age; 95 CI 0.91, 0.99; p 0.008).Conclusions WN viremia was frequently identified in Colorado blood donors during the 2003 WNV epidemic. The high frequency of WNF and subsequent physician visits among healthy blood donors suggest substantial morbidity from WNF in the general population. The inverse correlation between age and WNF is a new finding and its pathophysiology is unknown. [ABSTRACT FROM AUTHOR]

Coxiella burnetiiis a bacterium located worldwide that can cause Q fever when inhaled. We describe an outbreak of Q fever associated with a horse-boarding ranch that had acquired two herds of goats. We conducted case finding and cohort studies among persons who boarded horses on the ranch and ranchers and among residents in the surrounding community, and conducted sampling of the goats and environment, to determine risk factors for infection and guide public health interventions. Sixty-six ranchers and persons who boarded horses on the ranch were interviewed; 62 (94) were not professional ranchers. Twenty persons (53) of 38 persons tested had evidence of infection with C. burnetii. Contact with goats was associated with seropositivity, including having helped birth goats (relative risk [RR] 2.4, 95 confidence interval [CI] 1.6–3.6), having had contact with newborn goats (RR 2.3, CI 1.2–4.3), having vaccinated goats (RR 2.1, CI 1.3–3.5), having had contact with stillbirths or newborns that died (RR 2.1, CI 1.2–3.7), and having fed goats (RR 2.1, CI 1.0–4.3). Among 138 tested persons living within 1 mile of the ranch, 11 (8) demonstrated evidence of C. burnetiiinfection; eight seropositive persons (73) had no direct contact with the ranch. Testing of the soil and goats with an IS1111 polymerase chain reaction (PCR) assay confirmed the presence of C. burnetiiamong the herd and in the environment. This outbreak of Q fever was caused by exposure to infected goats, but exposure to the environment likely played a secondary role. Laypersons should not participate in the birthing process of goats; professionals who come into contact with birthing goats should be educated on reducing their infection risk. This is the first time an IS1111 PCR assay has been used in an outbreak investigation in the United States. [ABSTRACT FROM AUTHOR]