Craig Levy

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.

Modifiable Risk Factors for West Nile Virus Infection during an Outbreak—Arizona, 2010

West Nile virus (WNV) is the leading cause of mosquito-borne disease in the United States; however, risk factors for infection are poorly defined. We performed a case-control study to identify modifiable risk factors for WNV infection. Case-patients (N = 49) had laboratory evidence of recent WNV infection, whereas control-subjects (N = 74) had negative WNV serology. We interviewed participants, surveyed households, and assessed environmental data. WNV infection was associated with living in or near Water District X within Gilbert Township (adjusted odds ratio [aOR] 5.2; 95% confidence interval [95% CI] = 1.5-18.1), having water-holding containers in their yard (aOR 5.0; 95% CI = 1.5-17.3), and not working or attending school outside the home (aOR 2.4; 95% CI = 1.1-5.5). During this outbreak, WNV infection was likely primarily acquired peri-domestically with increased risk associated with potential mosquito larval habitats around the home and neighborhood.

Entomologic Investigations during an Outbreak of West Nile Virus Disease in Maricopa County, Arizona, 2010

Entomologic investigations were conducted during an intense outbreak of West Nile virus (WNV) disease in Maricopa County, Arizona during July 31-August 9, 2010. The investigations compared the East Valley outbreak area, and a demographically similar control area in northwestern metropolitan Phoenix where no human cases were reported. Five mosquito species were identified in each area, and species composition was similar in both areas. Significantly more Culex quinquefasciatus females were collected by gravid traps at Outbreak sites (22.2 per trap night) than at control sites (8.9 per trap night), indicating higher Cx. quinquefasciatus abundance in the outbreak area. Twenty-eight WNV TaqMan reverse transcription-polymerase chain reaction-positive mosquito pools were identified, including 24 of Cx. quinquefasciatus, 3 of Psorophora columbiae, and 1 of Culex sp. However, Cx. quinquefasciatus WNV infection rates did not differ between outbreak and control sites. At outbreak sites, 30 of 39 engorged Cx. quinquefasciatus had fed on birds, 8 of 39 on humans, and 1 of 39 on a lizard. At control sites, 20 of 20 identified blood meals were from birds. Data suggest that Cx. quinquefasciatus was the primary enzootic and epidemic vector of this outbreak. The most important parameters in the outbreak were vector abundance and blood meal analysis, which suggested more frequent contact between Cx. quinquefasciatus and human hosts in the outbreak area compared with the control area.

Annual Seroprevalence of Yersinia pestis in Coyotes as Predictors of Interannual Variation in Reports of Human Plague Cases in Arizona, United States

Although several health departments collect coyote blood samples for plague surveillance, the association between reported human cases and coyote seroprevalence rates remains anecdotal. Using data from an endemic region of the United States, we sought to quantify this association. From 1974 to 1998, about 2,276 coyote blood samples from four Arizona counties were tested for serological evidence of exposure to Yersinia pestis, the causative agent of plague. Using a titer threshold presumed to be indicative of recent infection (serum titers of ≥1:256), we found a statistically significant relationship between years with >17% sero-positive coyotes and years with two or more human cases reported. Moreover, when the annual coyote seroprevalence rates were dichotomized at 17%, 84% of the years were correctly classified using four biologically relevant meteorological variables in a linear regression. This is the first time a statistically significant temporal association between human plague cases and coyote seroprevalence rates has been shown. However, issues with data resolution and surveillance effort that potentially limit the public health utility of using coyote seroprevalence rates are discussed.

Co-Infection of Rickettsia rickettsii and Streptococcus pyogenes: Is Fatal Rocky Mountain Spotted Fever Underdiagnosed?

Rocky Mountain spotted fever, a tick-borne disease caused by Rickettsia rickettsii, is challenging to diagnose and rapidly fatal if not treated. We describe a decedent who was co-infected with group A β-hemolytic streptococcus and R. rickettsii. Fatal cases of Rocky Mountain spotted fever may be underreported because they present as difficult to diagnose co-infections.

Avian Hosts of West Nile Virus in Arizona

West Nile virus (WNV) causes sporadic outbreaks of human encephalitis in Phoenix, Arizona. To identify amplifying hosts of WNV in the Phoenix area, we blood-sampled resident birds and measured antibody prevalence following an outbreak in the East Valley of metropolitan Phoenix during summer, 2010. House sparrow (Passer domesticus), house finch (Haemorhous mexicanus), great-tailed grackle (Quiscalus mexicanus), and mourning dove (Zenaida macroura) accounted for most WNV infections among locally resident birds. These species roost communally after early summer breeding. In September 2010, Culex vector-avian host contact was 3-fold greater at communal bird roosts compared with control sites, as determined by densities of resting mosquitoes with previous vertebrate contact (i.e., blood-engorged or gravid mosquitoes). Because of the low competence of mourning doves, these were considered weak amplifiers but potentially effective free-ranging sentinels. Highly competent sparrows, finches, and grackles were predicted to be key amplifying hosts for WNV in suburban Phoenix.

Community Survey after Rabies Outbreaks, Flagstaff, Arizona, USA

Educational outreach should inform the public about dangers of translocation of wild animals and general aspects of rabies.

St. Louis encephalitis virus possibly transmitted through blood transfusion—Arizona, 2015

St. Louis encephalitis virus is a mosquito‐borne flavivirus that infrequently causes epidemic central nervous system infections. In the United States, blood donors are not screened for St. Louis encephalitis virus infection, and transmission through blood transfusion has not been reported. During September 2015, St. Louis encephalitis virus infection was confirmed in an Arizona kidney transplant recipient. An investigation was initiated to determine the infection source.

Human Rabies Postexposure Prophylaxis Knowledge and Retention Among Health Professionals by Using an Online Continuing Education Module: Arizona, 2012 to 2015

Rabies postexposure prophylaxis (PEP) is administered for rabies prevention after a human exposure to a potentially rabid animal, such as a bite. Previous studies have reported that rabies PEP is often inappropriately administered. Health professional education was proposed as one potential solution to address inappropriate PEP use. We assessed baseline knowledge, knowledge gain, and knowledge retention among health professionals in Arizona of rabies epidemiology and appropriate PEP administration. Maricopa County Department of Public Health created an online rabies PEP continuing education module and measured knowledge before and after module completion using a 10-question test. The same test was administered three times (pretest, posttest, and retention test at ≥3 months). To assess knowledge gain and retention, we compared median scores using nonparametric methods. A total of 302 respondents completed the pretest (median score, 60%) and posttest (median score, 90%; p < .001); 98 respondents completed all three tests with median scores 60% (pretest), 90% (posttest, p < .01), and 80% (retention test and compared with pretest, p < .01). Sixty-nine (70%) respondents improved their pretest to retention test score by a mean of 2.4 points out of a total 10 points (median: 2 points; range: −5 to 7 points). Only 48% of pretest respondents correctly answered that PEP should not be administered immediately to anyone bitten by a healthy dog. However, 81% and 70% answered correctly on the posttest (p < .0001) and retention test (p = .002), respectively. Respondents demonstrated rabies epidemiology and PEP knowledge gain and ≥3-month knowledge retention after completing the online continuing education module.