Paul Ettestad

Climatic and environmental patterns associated with hantavirus pulmonary syndrome, Four Corners region, United States.

To investigate climatic, spatial, temporal, and environmental patterns associated with hantavirus pulmonary syndrome (HPS) cases in the Four Corners region, we collected exposure site data for HPS cases that occurred in 1993 to 1995. Cases clustered seasonally and temporally by biome type and geographic location, and exposure sites were most often found in pinyon-juniper woodlands, grasslands, and Great Basin desert scrub lands, at elevations of 1,800 m to 2,500 m. Environmental factors (e.g., the dramatic increase in precipitation associated with the 1992 to 1993 El Niño) may indirectly increase the risk for Sin Nombre virus exposure and therefore may be of value in designing disease prevention campaigns.

Multistate outbreak of listeriosis associated with cantaloupe.

BACKGROUND Although new pathogen-vehicle combinations are increasingly being identified in produce-related disease outbreaks, fresh produce is a rarely recognized vehicle for listeriosis. We investigated a nationwide listeriosis outbreak that occurred in the United States during 2011. METHODS We defined an outbreak-related case as a laboratory-confirmed infection with any of five outbreak-related subtypes of Listeria monocytogenes isolated during the period from August 1 through October 31, 2011. Multistate epidemiologic, trace-back, and environmental investigations were conducted, and outbreak-related cases were compared with sporadic cases reported previously to the Listeria Initiative, an enhanced surveillance system that routinely collects detailed information about U.S. cases of listeriosis. RESULTS We identified 147 outbreak-related cases in 28 states. The majority of patients (127 of 147, 86%) were 60 years of age or older. Seven infections among pregnant women and newborns and one related miscarriage were reported. Of 145 patients for whom information about hospitalization was available, 143 (99%) were hospitalized. Thirty-three of the 147 patients (22%) died. Patients with outbreak-related illness were significantly more likely to have eaten cantaloupe than were patients 60 years of age or older with sporadic illness (odds ratio, 8.5; 95% confidence interval, 1.3 to ∞). Cantaloupe and environmental samples collected during the investigation yielded isolates matching all five outbreak-related subtypes, confirming that whole cantaloupe produced by a single Colorado farm was the outbreak source. Unsanitary conditions identified in the processing facility operated by the farm probably resulted in contamination of cantaloupes with L. monocytogenes. CONCLUSIONS Raw produce, including cantaloupe, can serve as a vehicle for listeriosis. This outbreak highlights the importance of preventing produce contamination within farm and processing environments.

Human Plague in the Southwestern United States, 1957–2004: Spatial Models of Elevated Risk of Human Exposure to Yersinia pestis

Abstract Plague is a rare but highly virulent flea-borne zoonotic disease caused by the Gram-negative bacterium Yersinia pestis Yersin. Identifying areas at high risk of human exposure to the etiological agent of plague could provide a useful tool for targeting limited public health resources and reduce the likelihood of misdiagnosis by raising awareness of the disease. We created logistic regression models to identify landscape features associated with areas where humans have acquired plague from 1957 to 2004 in the four-corners region of the United States (Arizona, Colorado, New Mexico, and Utah), and we extrapolated those models within a geographical information system to predict where plague cases are likely to occur within the southwestern United States disease focus. The probability of an area being classified as high-risk plague habitat increased with elevation up to ≈2,300 m and declined as elevation increased thereafter, and declined with distance from key habitat types (e.g., southern Rocky Mountain piñon—juniper [Pinus edulis Engelm. and Juniperus spp.], Colorado plateau piñon-juniper woodland, Rocky Mountain ponderosa pine (Pinus ponderosa P.& C. Lawson var. scopulorum), and southern Rocky Mountain juniper woodland and savanna). The overall accuracy of the model was >82%. Our most conservative model predicted that 14.4% of the four-corners region represented a high risk of peridomestic exposure to Y. pestis.

Gentamicin and Tetracyclines for the Treatment of Human Plague: Review of 75 Cases in New Mexico, 1985–1999

Streptomycin, an antimicrobial with limited availability, is the treatment of choice for plague, a fulminating and potentially epidemic disease that poses a bioterrorism concern. We evaluated the efficacy of gentamicin and tetracyclines for treating human plague. A medical record review was conducted on all 75 patients with plague who were reported in New Mexico during 1985-1999. Fifty patients were included in an analysis that compared streptomycin-treated patients (n=14) with those treated with gentamicin and/or a tetracycline (n=36). The mean numbers of fever days, hospital days, and complications and the number of deaths did not differ between patients treated with streptomycin and those treated with gentamicin. One patient who received tetracycline alone experienced a serious complication. Gentamicin alone or in combination with a tetracycline was as efficacious as streptomycin for treating human plague. The efficacy of a tetracycline alone could not be determined from the study.

Outbreak of Salmonellosis Linked to Live Poultry from a Mail-Order Hatchery

BACKGROUND Outbreaks of human salmonella infections are increasingly associated with contact with live poultry, but effective control measures are elusive. In 2005, a cluster of human salmonella Montevideo infections with a rare pattern on pulsed-field gel electrophoresis (the outbreak strain) was identified by PulseNet, a national subtyping network. METHODS In cooperation with public health and animal health agencies, we conducted multistate investigations involving patient interviews, trace-back investigations, and environmental testing at a mail-order hatchery linked to the outbreak in order to identify the source of infections and prevent additional illnesses. A case was defined as an infection with the outbreak strain between 2004 and 2011. RESULTS From 2004 through 2011, we identified 316 cases in 43 states. The median age of the patient was 4 years. Interviews were completed with 156 patients (or their caretakers) (49%), and 36 of these patients (23%) were hospitalized. Among the 145 patients for whom information was available, 80 (55%) had bloody diarrhea. Information on contact with live young poultry was available for 159 patients, and 122 of these patients (77%) reported having such contact. A mail-order hatchery in the western United States was identified in 81% of the trace-back investigations, and the outbreak strain was isolated from samples collected at the hatchery. After interventions at the hatchery, the number of human infections declined, but transmission continued. CONCLUSIONS We identified a prolonged multistate outbreak of salmonellosis, predominantly affecting young children and associated with contact with live young poultry from a mail-order hatchery. Interventions performed at the hatchery reduced, but did not eliminate, associated human infections, demonstrating the difficulty of eliminating salmonella transmission from live poultry.

Human plague in the USA: the importance of regional and local climate.

A 56-year time series of human plague cases (Yersinia pestis) in the western United States was used to explore the effects of climatic patterns on plague levels. We found that the Pacific Decadal Oscillation (PDO), together with previous plague levels and above-normal temperatures, explained much of the plague variability. We propose that the PDOs impact on plague is conveyed via its effect on precipitation and temperature and the effect of precipitation and temperature on plague hosts and vectors: warmer and wetter climate leading to increased plague activity and thus an increased number of human cases. Our analysis furthermore provides insights into the consistency of plague mechanisms at larger scales.

Persistent neuropsychological impairment associated with West Nile virus infection

West Nile virus infection can result in prolonged subjective complaints of cognitive and functional decline even in the absence of a neuroinvasive form of infection. Persistent cognitive and functional complaints could be a result of general somatic symptoms, emotional distress, or residual central nervous system damage or dysfunction. Most studies of cognition in postacute West Nile virus infection rely on self-report. This descriptive study aimed to document cognitive deficits in a sample of the 2003 infected population reported in New Mexico. Patients with clinically defined neuroinvasive disease or who were impaired on brief mental status screening were seen for comprehensive neuropsychological assessment. We found that one year after symptom onset, more than half of the sample had objectively measurable neuropsychological impairment in at least two cognitive domains. Impairment was not related to subjective complaints of physical or emotional distress, or premorbid intellectual abilities. Persistent cognitive impairment in West Nile virus infection may be due to prolonged or permanent damage to the central nervous system.

Fine-scale Identification of the Most Likely Source of a Human Plague Infection

We describe an analytic approach to provide fine-scale discrimination among multiple infection source hypotheses. This approach uses mutation-rate data for rapidly evolving multiple locus variable-number tandem repeat loci in probabilistic models to identify the most likely source. We illustrate the utility of this approach using data from a North American human plague investigation.

Climatic Predictors of the Intra- and Inter-Annual Distributions of Plague Cases in New Mexico Based on 29 Years of Animal-Based Surveillance Data

Within the United States, the majority of human plague cases are reported from New Mexico. We describe climatic factors involved in intra- and inter-annual plague dynamics using animal-based surveillance data from that state. Unlike the clear seasonal pattern observed at lower elevations, cases occur randomly throughout the year at higher elevations. Increasing elevation corresponded with delayed mean time in case presentation. Using local meteorological data (previous year mean annual precipitation, total degrees over 27 degrees C 3 years before and maximum winter temperatures 4 years before) we built a time-series model predicting annual case load that explained 75% of the variance in pet cases between years. Moreover, we found a significant correlation with observed annual human cases and predicted pet cases. Because covariates were time-lagged by at least 1 year, intensity of case loads can be predicted in advance of a plague season. Understanding associations between environmental and meteorological factors can be useful for anticipating future disease trends.

Misidentification of Yersinia pestis by Automated Systems, Resulting in Delayed Diagnoses of Human Plague Infections—Oregon and New Mexico, 2010–2011

One human plague case was reported in Oregon in September 2010 and another in New Mexico in May 2011. Misidentification of Yersinia pestis by automated identification systems contributed to delayed diagnoses for both cases.