title: Entomologic investigations during an outbreak of West Nile virus disease in Maricopa County, Arizona, 2010.
abstract: 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.
authors.affiliation: Division of Vector-Borne Diseases, Arboviral Diseases Branch, Centers for Disease Control and Prevention, Fort Collins, CO 80521, USA. mgodsey@cdc.gov
authors.forename: Marvin S
authors.initials: MS
authors.lastname: Godsey
authors.forename: Kristen
authors.initials: K
authors.lastname: Burkhalter
authors.forename: Ginger
authors.initials: G
authors.lastname: Young
authors.forename: Mark
authors.initials: M
authors.lastname: Delorey
authors.forename: Kirk
authors.initials: K
authors.lastname: Smith
authors.forename: John
authors.initials: J
authors.lastname: Townsend
authors.forename: Craig
authors.initials: C
authors.lastname: Levy
authors.forename: John-Paul
authors.initials: JP
authors.lastname: Mutebi
mesh_terms: D000818:Animals; D001130:Arizona / Q000453:epidemiology; D009033:Culicidae / Q000145:classification* / Q000821:virology; D004196:Disease Outbreaks; D005260:Female; D006801:Humans; D008875:Middle Aged; D011157:Population Dynamics; D012621:Seasons; D013045:Species Specificity; D013997:Time Factors; D014901:West Nile Fever / Q000453:epidemiology*; D055815:Young Adult