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Arbovirus Surveillance in the United StatesTable 1. States conducting selected West Nile virus surveillance activities, United States, 2004 and 2012*No. responding states (% with activity) % Difference fromSurveillance activity2012 20042004 to 2012Human surveillanceFormal surveillance system 50 (98) 49 (100) 2Active surveillance component 49 (29) 49 (47) 18Use official case definition 50 (88) 49 (88) 0Require reporting of encephalitis of unknown etiology 50 (48) 49 (63) 15To encourage reporting and to suggest a high index of suspicion, did you contactNeurologists 48 (50) 48 (60) 10Critical care specialists 48 (48) 49 (57) 9Infectious disease specialists 48 (58) 49 (82) 24Equine surveillanceFormal surveillance system 49 (90) 49 (94) 4Active surveillance component 44 (5) 46 (24) 19Designated public health veterinarian within the agency?Yes 50 (76) 49 (82) 6Avian surveillanceFormal avian death surveillance 49 (39) 49 (98) 59Active component 19 (10) 48 (44) 34Sentinel chicken surveillance 50 (10) – NAAdequate access to wildlife expertise within agency 50 (76) 49 (92) 16Mosquito surveillanceFormal surveillance system 49 (80) 49 (96) 16Collect information about mosquito surveillance from LHDs in state? (states only)Yes 49 (90) 49 (94) 4By species? 43 (86) 45 (80) +6Do most LHDs in your state conduct surveillance for (states only)Adult mosquitoes 44 (34) 44 (48) 14Larval mosquitoes 44 (18) 44 (30) 11Adequate access to entomologist in agency or by contract 50 (64) 49 (71) 7*–, not asked; NA, not applicable; asked; LHDs, local health departments.In 2012, 92% of states had some public health laboratorycapacity for WNV testing to support human surveillanceand 84% to support mosquito surveillance (Table 2). Most(93%) states tested human specimens for IgM and mosquitospecimens by using PCR (72%) or culture (13%). Relativelyfew states tested human specimens by using PCR(13%) or culture (2%). When compared with 2004, manyfewer laboratories conducted IgG, PCR and culture tests onhuman specimens in 2012. Testing methods for mosquitoesdid not change greatly.We also assessed state public health laboratory capacityto test for 10 arboviruses, in addition to WNV, in humanserum or CSF specimens. St. Louis encephalitis (SLE)virus testing capacity was most common (34 laboratories),followed by testing for eastern equine encephalitis (EEE)(24), western equine encephalitis (WEE) (16), LaCrosse(16), dengue (9), Powassan (4), chikungunya (2), Coloradotick fever (2), yellow fever (2), and Japanese encephalitis(1) viruses. These laboratories reported performing 41,159tests for arboviruses in 2012, of which 19,180 (46.6%)were for WNV. Of these tests, the highest percentage ofpositive test results was for dengue virus (137/328, 41.8%),followed by WNV (2,953/19,178, 15.4%), Powassan virus(62/1,257, 4.9%), LaCrosse virus (121/3,372, 3.6%), SLEvirus (164/8,216, 2.0%), Colorado tick fever virus (2/139,1.4%), and WEE virus (12/3,888, 0.03%).Although many laboratories had the capability to test forarboviruses other than WNV, not all routinely did so. Overall,26 (60%) of 43 responding laboratories reported routinelytesting human CSF specimens submitted for WNV for atleast 1 other arbovirus. Of these 26 laboratories, 24 routinelytested for SLE virus, 12 for EEE virus, 6 for WEE virus, 5 forLaCrosse virus, and 2 for Powassan viruse. Among laboratoriesserving the 45 states that either test mosquitoes or useanother laboratory, 24 reported routinely testing mosquitopools for SLE virus, 22 for EEE virus, and 13 for the Californiaserogroup. To manage federal WNV surveillance fundingreductions over the past 5 years, 57% of states reportedeliminating avian death surveillance, 58% decreased mosquitotrapping, 68% decreased mosquito testing, and 46%decreased the number of human specimens tested for WNV.The responses from the 6 LHDs with ELC WNV surveillancesupport to each surveillance capacity were similarto those from the 50 states in 2004 and 2012, exceptfor laboratory capacity. Currently, only 4 ELC-supportedLHDs do some of their own WNV testing.Arboviral Surveillance in LHDs withoutFederal WNV Surveillance SupportThe 15 LHDs without ELC grants included 13 with highWNV burden and 2 with recent dengue transmission. TheseLHDs were generally less likely to take an active role inEmerging Infectious Diseases • www.cdc.gov/eid • Vol. 21, No. 7, July 2015 1161