The tools available to vector control districts (VCDs) to collect mosquito surveillance data are constantly evolving. As more VCDs obtain real-time polymerase chain reaction (PCR) instruments and the costs associated with computing power and next-generation sequencing continue to decrease, the option of generating useful molecular data in-house becomes more viable. Measures such as arbovirus testing and genotyping for insecticide resistance mutations using RT-qPCR, and identifying species used for mosquito bloodmeals with next-generation sequencing or Sanger sequencing are examples. In this study we identify mosquito host bloodmeal species using Nanopore sequencing from Oxford Nanopore Technologies. We used MinION and Flongle flow cells and a Mk1C device to sequence 96 barcoded amplicon samples in a single sequencing run, and share details of data analysis using the free-to-use Galaxy bioinformatics platform. After sequencing the same samples with Sanger sequencing, we conclude that Nanopore sequencing is better at identifying species in mixed bloodmeals. This work demonstrates a potential use of nanopore sequencing by VCDs with basic biology laboratory and computing equipment.

The 2014 chikungunya outbreak in the Dominican Republic resulted in intense local transmission, with high postoutbreak seroprevalence. The resulting population immunity will likely minimize risk for another large outbreak through 2035, but changes in population behavior or environmental conditions or emergence of different virus strains could lead to increased transmission.

Cache Valley virus (CVV), a mosquito-borne orthobunyavirus, causes epizootics in ruminants characterized by congenital malformations and fetal death in North America. Only seven human infections have been identified; limited information exists on its potential as a human teratogen. Diagnosis of CVV infections relies on the plaque reduction neutralization test (PRNT), which requires live virus, is time-consuming, and cannot differentiate between recent and past infections. To improve diagnostics for CVV, we developed an IgM antibody capture ELISA (MAC-ELISA) for detection of anti-CVV human IgM in diagnostic specimens that can be performed faster than PRNT and is specific to IgM, which is essential to determine the timing of infection. Conjointly, a cell line constitutively expressing human-murine chimeric antibody with the variable regions of monoclonal antibody CVV-17 and constant regions of human IgM was developed to provide positive control material. The new cell line produced antibody with reactivity in the assay equivalent to that of a human serum sample positive for anti-CVV IgM. Five of seven archived human specimens diagnostically confirmed as CVV positive tested positive in the MAC-ELISA, whereas 44 specimens confirmed positive for another arboviral infection tested negative, showing good initial correlation of the CVV MAC-ELISA. Two of 27 previously collected serum samples from febrile patients in Yucatán, Mexico, who tested negative for a recent flaviviral or alphaviral infection were positive in both the MAC-ELISA and PRNT, indicating a possible recent infection with CVV or related orthobunyavirus. The MAC-ELISA described here will aid in making diagnostics more widely available for CVV in public health laboratories.

West Nile virus (WNV) is the most common cause of human arboviral disease in the contiguous United States, where only lineage 1 (L1) WNV had been found. In 2023, an immunocompetent patient was hospitalized in Nebraska with West Nile neuroinvasive disease and multisystem organ failure. Testing at the Centers for Disease Control and Prevention indicated an unusually high viral load and acute antibody response. Upon sequencing of serum and cerebrospinal fluid, we detected lineage 3 (L3) and L1 WNV genomes. L3 WNV had previously only been found in Central Europe in mosquitoes. The identification of L3 WNV in the United States and the observed clinical and laboratory features raise questions about the potential effect of L3 WNV on the transmission dynamics and pathogenicity of WNV infections. Determining the distribution and prevalence of L3 WNV in the United States and any public health and clinical implications is critical.

The recovery of a Haemaphysalis longicornis Neumann (Acari: Ixodidae) tick from a dog in Benton County, Arkansas, in 2018 triggered a significant environmental sampling effort in Hobbs State Park Conservation Area. The objective of the investigation was to assess the tick population density and diversity, as well as identify potential tick-borne pathogens that could pose a risk to public health. During a week-long sampling period in August of 2018, a total of 6,154 ticks were collected, with the majority identified as Amblyomma americanum (L), (Acari: Ixodidae) commonly known as the lone star tick. No H. longicornis ticks were found despite the initial detection of this species in the area. This discrepancy highlights the importance of continued monitoring efforts to understand the dynamics of tick populations and their movements. The investigation also focused on pathogen detection, with ticks being pooled by species, age, and sex before being processed with various bioassays. The results revealed the presence of several tick-borne pathogens, including agents associated with ehrlichiosis (n = 12), tularemia (n = 2), and Bourbon virus (BRBV) disease (n = 1), as well as nonpathogenic rickettsial and anaplasmosis organisms. These findings emphasize the importance of public health messaging to raise awareness of the risks associated with exposure to tick-borne pathogens. Prevention measures, such as wearing protective clothing, using insect repellent, and conducting regular tick checks, should be emphasized to reduce the risk of tick-borne diseases. Continued surveillance efforts and research are also essential to improve our understanding of tick-borne disease epidemiology and develop effective control strategies.

BACKGROUND: In 2021, four patients who had received solid organ transplants in the USA developed encephalitis beginning 2-6 weeks after transplantation from a common organ donor. We describe an investigation into the cause of encephalitis in these patients. METHODS: From Nov 7, 2021, to Feb 24, 2022, we conducted a public health investigation involving 15 agencies and medical centres in the USA. We tested various specimens (blood, cerebrospinal fluid, intraocular fluid, serum, and tissues) from the organ donor and recipients by serology, RT-PCR, immunohistochemistry, metagenomic next-generation sequencing, and host gene expression, and conducted a traceback of blood transfusions received by the organ donor. FINDINGS: We identified one read from yellow fever virus in cerebrospinal fluid from the recipient of a kidney using metagenomic next-generation sequencing. Recent infection with yellow fever virus was confirmed in all four organ recipients by identification of yellow fever virus RNA consistent with the 17D vaccine strain in brain tissue from one recipient and seroconversion after transplantation in three recipients. Two patients recovered and two patients had no neurological recovery and died. 3 days before organ procurement, the organ donor received a blood transfusion from a donor who had received a yellow fever vaccine 6 days before blood donation. INTERPRETATION: This investigation substantiates the use of metagenomic next-generation sequencing for the broad-based detection of rare or unexpected pathogens. Health-care workers providing vaccinations should inform patients of the need to defer blood donation for at least 2 weeks after receiving a yellow fever vaccine. Despite mitigation strategies and safety interventions, a low risk of transfusion-transmitted infections remains. FUNDING: US Centers for Disease Control and Prevention (CDC), the Biomedical Advanced Research and Development Authority, and the CDC Epidemiology and Laboratory Capacity Cooperative Agreement for Infectious Diseases.

Ivermectin (IVM)-treated birds provide the potential for targeted control of Culex mosquitoes to reduce West Nile virus (WNV) transmission. Ingestion of IVM increases mosquito mortality, which could reduce WNV transmission from birds to humans and in enzootic maintenance cycles affecting predominantly bird-feeding mosquitoes and from birds to humans. This strategy might also provide an alternative method for WNV control that is less hampered by insecticide resistance and the logistics of large-scale pesticide applications. Through a combination of field studies and modeling, we assessed the feasibility and impact of deploying IVM-treated birdfeed in residential neighborhoods to reduce WNV transmission. We first tracked 105 birds using radio telemetry and radio frequency identification to monitor their feeder usage and locations of nocturnal roosts in relation to five feeder sites in a neighborhood in Fort Collins, Colorado. Using these results, we then modified a compartmental model of WNV transmission to account for the impact of IVM on mosquito mortality and spatial movement of birds and mosquitoes on the neighborhood level. We found that, while the number of treated lots in a neighborhood strongly influenced the total transmission potential, the arrangement of treated lots in a neighborhood had little effect. Increasing the proportion of treated birds, regardless of the WNV competency status, resulted in a larger reduction in infection dynamics than only treating competent birds. Taken together, model results indicate that deployment of IVM-treated feeders could reduce local transmission throughout the WNV season, including reducing the enzootic transmission prior to the onset of human infections, with high spatial coverage and rates of IVM-induced mortality in mosquitoes. To improve predictions, more work is needed to refine estimates of daily mosquito movement in urban areas and rates of IVM-induced mortality. Our results can guide future field trials of this control strategy.

In 2020, Montana, USA, reported a large increase in Colorado tick fever (CTF) cases. To investigate potential causes of the increase, we conducted a case-control study of Montana residents who tested positive or negative for CTF during 2020, assessed healthcare providers' CTF awareness and testing practices, and reviewed CTF testing methods. Case-patients reported more time recreating outdoors on weekends, and all reported finding a tick on themselves before illness. No consistent changes were identified in provider practices. Previously, only CTF serologic testing was used in Montana. In 2020, because of SARS-CoV-2 testing needs, the state laboratory sent specimens for CTF testing to the Centers for Disease Control and Prevention, where more sensitive molecular methods are used. This change in testing probably increased the number of CTF cases detected. Molecular testing is optimal for CTF diagnosis during acute illness. Tick bite prevention measures should continue to be advised for persons doing outdoor activities.

The reservoir for zoonotic o'nyong-nyong virus (ONNV) has remained unknown since this virus was first recognized in Uganda in 1959. Building on existing evidence for mosquito blood-feeding on various frugivorous bat species in Uganda, and seroprevalence for arboviruses among bats in Uganda, we sought to assess if serum samples collected from bats in Uganda demonstrated evidence of exposure to ONNV or the closely related zoonotic chikungunya virus (CHIKV). In total, 652 serum samples collected from six bat species were tested by plaque reduction neutralization test (PRNT) for neutralizing antibodies against ONNV and CHIKV. Forty out of 303 (13.2%) Egyptian rousettes from Maramagambo Forest and 1/13 (8%) little free-tailed bats from Banga Nakiwogo, Entebbe contained neutralizing antibodies against ONNV. In addition, 2/303 (0.7%) of these Egyptian rousettes contained neutralizing antibodies to CHIKV, and 8/303 (2.6%) contained neutralizing antibodies that were nonspecifically reactive to alphaviruses. These data support the interepidemic circulation of ONNV and CHIKV in Uganda, although Egyptian rousette bats are unlikely to serve as reservoirs for these viruses given the inconsistent occurrence of antibody-positive bats.

With increasing use of rituximab and other B-cell depleting monoclonal antibodies for multiple indications, infectious complications are being recognized. We summarize clinical findings of patients on rituximab with arboviral diseases identified through literature review or consultation with the Centers for Disease Control and Prevention. We identified 21 patients on recent rituximab therapy who were diagnosed with an arboviral disease caused by West Nile, tick-borne encephalitis, eastern equine encephalitis, Cache Valley, Jamestown Canyon, and Powassan viruses. All reported patients had neuroinvasive disease. The diagnosis of arboviral infection required molecular testing in 20 (95%) patients. Median illness duration was 36 days (range, 12 days-1 year) and 15/19 (79%) patients died from their illness. Patients on rituximab with arboviral disease can have a severe or prolonged course with an absence of serologic response. Patients should be counseled about mosquito and tick bite prevention when receiving rituximab and other B-cell depleting therapies.

BACKGROUND: Cache Valley virus (CVV) is a mosquito-borne virus that is a rare cause of disease in humans. In the Fall of 2020, a patient developed encephalitis six weeks following kidney transplantation and receipt of multiple blood transfusions. METHODS: After ruling out more common etiologies, metagenomic next-generation sequencing (mNGS) of cerebrospinal fluid (CSF) was performed. We reviewed the medical histories of the index kidney recipient, organ donor, and recipients of other organs from the same donor and conducted a blood traceback investigation to evaluate blood transfusion as a possible source of infection in the kidney recipient. We tested patient specimens by reverse transcription-polymerase chain reaction (RT-PCR), plaque reduction neutralization test (PRNT), cell culture, and whole genome sequencing. RESULTS: CVV was detected in CSF from the index patient by mNGS, and this result was confirmed by RT-PCR, viral culture, and additional whole genome sequencing. The organ donor and other organ recipients had no evidence of infection with CVV by molecular or serologic testing. Neutralizing antibodies against CVV were detected in serum from a donor of red blood cells received by the index patient immediately prior to transplant. CVV neutralizing antibodies were also detected in serum from a patient who received the co-component plasma from the same blood donation. CONCLUSION: Our investigation demonstrates probable CVV transmission through blood transfusion. Clinicians should consider arboviral infections in unexplained meningoencephalitis after blood transfusion or organ transplantation. The use of mNGS testing might facilitate detection of rare, unexpected infections, particularly in immunocompromised patients.

In the past few decades, reported human cases of Colorado tick fever in the western United States have decreased dramatically. The goal of this study was to conduct surveillance for Colorado tick fever virus (CTFV) in Dermacentor ticks in recreational sites in Colorado, Wyoming, and California to determine whether the virus is still present in Dermacentor ticks from these states. Surveillance focused on regions where surveys had been conducted in the 1950s, 1960s, and 1970s. Adult Rocky Mountain wood ticks (Dermacentor andersoni), Pacific Coast ticks (Dermacentor occidentalis), and winter ticks (Dermacentor albipictus) were tested by PCR. A subset of PCR-positive D. andersoni ticks (n=7) were cultured in Vero cells. CTFV-positive Rocky Mountain wood ticks were found in all states: Colorado (58% prevalence), Wyoming (21%), and California (4%). Although no winter ticks tested positive, Pacific Coast ticks tested positive in one county (Siskiyou County, 15% prevalence) and were positive only in a location that also maintained Rocky Mountain wood ticks and golden mantled ground squirrels, a known CTFV host. In summary, CTFV is prevalent in D. andersoni and D. occidentalis in regions where they are sympatric in California and in D. andersoni in Colorado and Wyoming. Although the number of human CTFV cases has declined dramatically, this decrease in reported disease does not appear to be due to the disappearance or even the decline in prevalence of this virus in ticks in historically endemic regions of the country.

West Nile virus (WNV) IgM antibodies typically indicate a recent infection. However, WNV IgM antibodies can remain detectable for months to years following illness onset. We found that 23% (11/47) of samples tested with a WNV ELISA and 43% (20/47) of samples tested with WNV microsphere immunoassay (MIA) at 16-19 months following WNV illness onset were positive for IgM antibodies. The proportion of samples testing positive for WNV IgM by ELISA decreased over time, but 5% (2/44) of individuals remained positive at 60-63 months after their acute illness and 4% (2/50) were WNV IgM equivocal at 72-81 months. Testing by MIA showed the same general trend of decreased proportion positive over time though the rates of positivity were higher at most time points compared with the ELISA, including 6% (3/50) of participant's samples identified as IgM positive by MIA at 72-81 months post their acute illness. With the MIA, there also was a high proportion of samples with nonspecific results at each time point; average of 23% across all time points. Clinicians and public health officials should consider these findings along with clinical and epidemiologic data when interpreting WNV IgM antibody test results.

West Nile virus (WNV) is the most common domestic arbovirus in the United States. During 2018, WNV was transmitted through solid organ transplantation to 2 recipients who had neuroinvasive disease develop. Because of increased illness and death in transplant recipients, organ procurement organizations should consider screening during region-specific WNV transmission months.

West Nile virus activity was evaluated within an island waterbird nesting colony with > 1,250 birds at Riverside Reservoir, Weld County, Colorado, USA. To avoid disturbance of nesting birds, blood-engorged mosquitoes (Culex tarsalis) were used to sample blood indirectly from birds rather than capturing, sampling, and releasing live birds. Local virus activity was confirmed by West Nile virus-positive feather samples from 26% of 46 carcasses collected during monthly visits to the colony from June to September 2009, including American White Pelican (Pelecanus erythrorhynchos; n = 7), California Gull (Larus californicus; n = 1), Snowy Egret (Egretta thula; n = 2), and Cattle Egret (Bubulcus ibis; n = 2). Of 22 blood-engorged mosquitoes collected and the blood meal host identified to species, one West Nile virus infection was detected (putatively from a Snowy Egret), and West Nile virus-specific antibodies were detected in eight samples: Snowy Egret (n = 5), Great Blue Heron (Ardea herodias; n = 2), and American White Pelican (n = 1). The engorgement rate of female Culex tarsalis at the nesting colony was 34%, sixfold higher than that at a nearby mainland site of 5.3%. The utilization of mosquitoes for sampling blood from wild animals may have broader application, and potentially reduce human disturbance of sensitive nesting bird species. © 2021 The Waterbird Society. All rights reserved.

West Nile virus (WNV) and Zika virus (ZIKV) are mosquito-borne viruses in the family Flaviviridae. Residents in, and travelers to, areas where the viruses are circulating are at risk for infection, and both viruses can cause an acute febrile illness. Given known cross-reactivity in flavivirus serologic assays, it is possible a patient with acute WNV infection could be misdiagnosed as having ZIKV infection if appropriate testing is not conducted. To understand how frequently persons with WNV infection have detectable cross-reactive ZIKV immunoglobulin M (IgM) antibody, we used archived serum samples from patients in the United States with recent WNV infection confirmed by a microsphere-based immunoassay test for IgM antibody and neutralizing antibody testing. Samples were tested for ZIKV IgM antibody with the Centers for Disease Control and Prevention (CDC) ZIKV IgM antibody capture enzyme-linked immunosorbent assay. Among 153 sera from patients with acute WNV infection, the ZIKV IgM antibody result was positive in 56 (37%; 95% confidence interval [CI] 29-44%) and equivocal in 28 (18%; 95% CI 13-25%). With 55% of samples having cross-reactive antibodies, it is important for health care providers to request appropriate testing based on the most likely cause of a patient's possible arboviral infection considering their clinical symptoms and signs, travel history, and place of residence. For cases where the epidemiology does not support the preliminary IgM findings, confirmatory neutralizing antibody testing should be performed. These measures will avoid an incorrect diagnosis of ZIKV infection, based on cross-reactive antibodies, in a person truly infected with WNV.

Eastern equine encephalitis virus (EEEV) is an arbovirus in the family Togaviridae, genus Alphavirus, found in North America and associated with freshwater/hardwood swamps in the Atlantic, Gulf Coast, and Great Lakes regions. EEEV disease in humans is rare but causes substantial illness and death. To investigate the molecular epidemiology and microevolution of EEEV from a fatal case in Alabama, USA, in 2019, we used next-generation sequencing of serum and cerebrospinal fluid (CSF). Phylogenetic inference indicated that the infecting strain may be closely related to isolates from Florida detected during 2010-2014, suggesting potential seeding from Florida. EEEV detected in serum displayed a higher degree of variability with more single-nucleotide variants than that detected in the CSF. These data refine our knowledge of EEEV molecular epidemiologic dynamics in the Gulf Coast region and demonstrate potential quasispecies bottlenecking within the central nervous system of a human host.

BACKGROUND: Heartland virus (HRTV), a recently reclassified member of the genus Bandavirus, family Phenuiviridae, was first isolated in 2009 from a Missouri farmer exhibiting leukopenia and thrombocytopenia with suspected ehrlichiosis. Since then, more HRTV cases have been diagnosed, and firstline laboratory diagnostic assays are needed to identify future infections Objectives. We sought to develop rapid and reliable IgM and IgG microsphere immunoassays (MIAs) to test sera of patients suspected of having HRTV infection, and to distinguish between recent and past infections. STUDY DESIGN: Heartland virus antigen was captured by an anti-HRTV monoclonal antibody covalently bound to microspheres. Antibodies in human sera from confirmed HRTV-positive and negative cases were reacted with the microsphere complexes and detected using a BioPlex® 200 instrument. Assay cutoffs were determined by receiver operator characteristic analysis of the normalized test output values, equivocal zones for each assay were defined, and sensitivities, specificities, accuracies, and imprecision values were calculated. RESULTS: Sensitivities, specificities and accuracies of the IgM and IgG MIAs were all >95 %. Both tests were precise within and between assay plates, and cross-reactivity with other arboviruses was not observed. CONCLUSIONS: HRTV IgM and IgG MIAs are accurate and rapid first-line methods to serologically identify recent and past HRTV infections.

Japanese encephalitis (JE) is a vaccine-preventable, mosquito-borne disease. Substantial progress with JE control in Asia has been made during the past decade, with most endemic countries now having JE vaccination programs, commonly using live attenuated SA14-14-2 JE vaccine (CD-JEV). If a child develops encephalitis during the weeks to months following CD-JEV vaccination and anti-JE virus IgM (JE IgM) antibody is detected in serum, the question arises if this is JE virus infection indicating vaccine failure, or persistent JE IgM antibody postvaccination. To better understand JE IgM seropositivity following vaccination, sera from 268 children from a previous CD-JEV study were tested by two different JE IgM assays to determine JE IgM antibody frequency on days 28, 180, and 365 postvaccination. With the CDC JE IgM antibody capture ELISA (MAC-ELISA), 110 children (41%) had JE IgM positive or equivocal results on their day 28 sample, and eight (3%) and two (1%) had positive or equivocal results on day 180 and day 365 samples, respectively. With the Inbios JE Detect™ MAC-ELISA, 118 (44%) children had positive or equivocal results on day 28 sample, and three (1%) and one (0.4%) had positive or equivocal results on day 180 and day 365 samples, respectively. Our results indicate that more than 40% children vaccinated with CD-JEV can have JE IgM antibodies in their serum at 1 month postvaccination but JE IgM antibody is rare by 6 months. These data will help healthcare workers assess the likelihood that JE IgM antibodies in the serum of a child with encephalitis after vaccination are vaccine related.

BACKGROUND: In fall 2017, 3 solid organ transplant (SOT) recipients from a common donor developed encephalitis within 1 week of transplantation, prompting suspicion of transplant-transmitted infection. Eastern equine encephalitis virus (EEEV) infection was identified during testing of endomyocardial tissue from the heart recipient. METHODS: We reviewed medical records of the organ donor and transplant recipients and tested serum, whole blood, cerebrospinal fluid, and tissue from the donor and recipients for evidence of EEEV infection by multiple assays. We investigated blood transfusion as a possible source of organ donor infection by testing remaining components and serum specimens from blood donors. We reviewed data from the pretransplant organ donor evaluation and local EEEV surveillance. RESULTS: We found laboratory evidence of recent EEEV infection in all organ recipients and the common donor. Serum collected from the organ donor upon hospital admission tested negative, but subsequent samples obtained prior to organ recovery were positive for EEEV RNA. There was no evidence of EEEV infection among donors of the 8 blood products transfused into the organ donor or in products derived from these donations. Veterinary and mosquito surveillance showed recent EEEV activity in counties nearby the organ donor's county of residence. Neuroinvasive EEEV infection directly contributed to the death of 1 organ recipient and likely contributed to death in another. CONCLUSIONS: Our investigation demonstrated EEEV transmission through SOT. Mosquito-borne transmission of EEEV to the organ donor was the likely source of infection. Clinicians should be aware of EEEV as a cause of transplant-associated encephalitis.

Among 39 children hospitalized in Colorado with aseptic meningitis or encephalitis, 16 (41%) had an etiology identified, including 2 (5%) with West Nile virus infection. Despite extensive testing, no other arboviral infections were identified. Arboviral infection should be considered in children with neuroinvasive disease during arboviral season with testing directed toward viruses endemic to the region and type of exposure.

Background: Heartland virus (HRTV) was first described as a human pathogen in 2012. From 2013 to 2017, the Centers for Disease Control and Prevention (CDC) implemented a national protocol to evaluate patients for HRTV disease, better define its geographic distribution, epidemiology, and clinical characteristics, and develop diagnostic assays for this novel virus. Methods: Individuals aged >/=12 years whose clinicians contacted state health departments or the CDC about testing for HRTV infections were screened for recent onset of fever with leukopenia and thrombocytopenia. A questionnaire was administered to collect data on demographics, risk factors, and signs and symptoms; blood samples were tested for the presence of HRTV RNA and neutralizing antibodies. Results: Of 85 individuals enrolled and tested, 16 (19%) had evidence of acute HRTV infection, 1 (1%) had past infection, and 68 (80%) had no infection. Patients with acute HRTV disease were residents of 7 states, 12 (75%) were male, and the median age (range) was 71 (43-80) years. Illness onset occurred from April to September. The majority reported fatigue, anorexia, nausea, headache, confusion, arthralgia, or myalgia. Fourteen (88%) cases were hospitalized; 2 (13%) died. Fourteen (88%) participants reported finding a tick on themselves in the 2 weeks before illness onset. HRTV-infected individuals were significantly older (P < .001) and more likely to report an attached tick (P = .03) than uninfected individuals. Conclusions: Health care providers should consider HRTV disease testing in patients with an acute febrile illness with either leukopenia or thrombocytopenia not explained by another condition or who were suspected to have a tickborne disease but did not improve following appropriate treatment.

In 2016, four clusters of local mosquitoborne Zika virus transmission were identified in Miami-Dade County, Florida, USA, generating "red zones" (areas into which pregnant women were advised against traveling). The Miami-Dade County Mosquito Control Division initiated intensive control activities, including property inspections, community education, and handheld sprayer applications of larvicides and adulticides. For the first time, the Mosquito Control Division used a combination of areawide ultralow-volume adulticide and low-volume larvicide spraying to effectively control Aedes aegypti mosquitoes, the primary Zika virus vector within the county. The number of mosquitoes rapidly decreased, and Zika virus transmission was interrupted within the red zones immediately after the combination of adulticide and larvicide spraying.

Zika virus (ZIKV) was first discovered in 1947 in Uganda but was not considered a public health threat until 2007 when it found to be the source of epidemic activity in Asia. Epidemic activity spread to Brazil in 2014 and continued to spread throughout the tropical and subtropical regions of the Americas. Despite ZIKV being zoonotic in origin, information about transmission, or even exposure of non-human vertebrates and mosquitoes to ZIKV in the Americas, is lacking. Accordingly, from February 2017 to March 2018, we sought evidence of sylvatic ZIKV transmission by sampling whole blood from approximately 2000 domestic and wild vertebrates of over 100 species in West-Central Brazil within the active human ZIKV transmission area. In addition, we collected over 24,300 mosquitoes of at least 17 genera and 62 species. We screened whole blood samples and mosquito pools for ZIKV RNA using pan-flavivirus primers in a real-time reverse-transcription polymerase chain reaction (RT-PCR) in a SYBR Green platform. Positives were confirmed using ZIKV-specific envelope gene real-time RT-PCR and nucleotide sequencing. Of the 2068 vertebrates tested, none were ZIKV positive. Of the 23,315 non-engorged mosquitoes consolidated into 1503 pools tested, 22 (1.5%) with full data available showed some degree of homology to insect-specific flaviviruses. To identify previous exposure to ZIKV, 1498 plasma samples representing 62 species of domestic and sylvatic vertebrates were tested for ZIKV-neutralizing antibodies by plaque reduction neutralization test (PRNT90). From these, 23 (1.5%) of seven species were seropositive for ZIKV and negative for dengue virus serotype 2, yellow fever virus, and West Nile virus, suggesting potential monotypic reaction for ZIKV. Results presented here suggest no active transmission of ZIKV in non-human vertebrate populations or in alternative vector candidates, but suggest that vertebrates around human populations have indeed been exposed to ZIKV in West-Central Brazil.

Since its recent discovery, Bourbon virus has been isolated from a human and ticks. To assess exposure of potential vertebrate reservoirs, we assayed banked serum and plasma samples from wildlife and domestic animals in Missouri, USA, for Bourbon virus-neutralizing antibodies. We detected high seroprevalence in raccoons (50%) and white-tailed deer (86%).

Tick-borne infections represent a significant health risk each year in the United States. Immunocompromised patients are typically at risk of more severe disease manifestations than their immunocompetent counterparts. Here we report a case of a newly emerging phlebovirus, Heartland virus, in a heart transplant recipient. This article is protected by copyright. All rights reserved.

To explain the patchy distribution of West Nile virus (WNV), we propose that avian immunity encountered by Culex vectors regulates WNV transmission, particularly at communal bird roosts. To test this hypothesis, we selected two test sites with communally roosting American robins (Turdus migratorius) and two control sites that lacked communal roosts. The density of vector-vertebrate contacts, represented by engorged Culex pipiens, was 23-fold greater at test sites compared to control sites, and the density of blood-engorged Cx. pipiens measured in resting mosquito traps correlated positively with the presence of robins and negatively with the presence of other birds, confirming an attraction to robins for blood feeding. WNV transmission was alternately up-regulated (amplification) and down-regulated (suppression) at both test sites. At one test site, infection in resting Cx. pipiens surged from zero to 37.2 per thousand within four weeks, and robin immunity rose from 8.4% to 64% before reducing to 33%. At this site, ten potentially infectious contacts between vector and vertebrates (including nine robins and a mourning dove [Zenaida macroura]) were documented. Infectious vector-vertebrate contacts were absent from control sites. The use of infectious vector-vertebrate contacts, rather than infected mosquitoes, to evaluate a transmission focus is novel.

Background: Few studies have assessed the duration of humoral immunity following yellow fever (YF) vaccination in a non-endemic population. We evaluated seropositivity among U.S. resident travelers based on time post-vaccination. Methods: We identified serum samples from U.S. travelers with YF virus-specific plaque reduction neutralization testing (PRNT) performed at CDC from 1988-2016. Analyses were conducted to assess the effect of time since vaccination on neutralizing antibody titer counts. Results: Among 234 travelers who had neutralizing antibody testing performed on a specimen obtained >/=1 month after vaccination, 13 received multiple YF vaccinations and 221 had one dose of YF vaccine reported. All 13 who received more than one dose of YF vaccine had a positive PRNT regardless of the amount time since most recent vaccination. Among the 221 travelers with one reported dose of YF vaccine, 155 (70%) were vaccinated within 10 years (range 1 month-9 years) and 66 (30%) were vaccinated >/=10 years (range 10-53 years) prior to serum collection. Among the 155 individuals vaccinated <10 years prior to serum collection, 146 (94%) had a positive PRNT compared to 82% (54/66) of individuals vaccinated >/=10 years prior to serum collection (p = 0.01). Post-vaccination PRNT titers showed a time-dependent decrease. Individuals with immunocompromising conditions were less likely to have a positive PRNT (77%) compared to those who were not immunocompromised (92%; p = 0.04). Conclusion: Although the percentage of vaccinees with a positive PRNT and antibody titers decreased over time, a single dose of YF vaccine provided long-lasting protection in the majority of U.S. travelers. A booster dose could be considered for certain travelers who are planning travel to a high risk area based on immune competence and time since vaccination.

When introduced into a naive population, chikungunya virus generally spreads rapidly, causing large outbreaks of fever and severe polyarthralgia. We randomly selected households in the U.S. Virgin Islands (USVI) to estimate seroprevalence and symptomatic attack rate for chikungunya virus infection at approximately 1 year following the introduction of the virus. Eligible household members were administered a questionnaire and tested for chikungunya virus antibodies. Estimated proportions were calibrated to age and gender of the population. We enrolled 509 participants. The weighted infection rate was 31% (95% confidence interval [CI]: 26-36%). Among those with evidence of chikungunya virus infection, 72% (95% CI: 65-80%) reported symptomatic illness and 31% (95% CI: 23-38%) reported joint pain at least once per week approximately 1 year following the introduction of the virus to USVI. Comparing rates from infected and noninfected study participants, 70% (95% CI: 62-79%) of fever and polyarthralgia and 23% (95% CI: 9-37%) of continuing joint pain in patients infected with chikungunya virus were due to their infection. Overall, an estimated 43% (95% CI: 33-52%) of the febrile illness and polyarthralgia in the USVI population during the outbreak was attributable to chikungunya virus and only 12% (95% CI: 7-17%) of longer term joint pains were attributed to chikungunya virus. Although the rates of infection, symptomatic disease, and longer term joint symptoms identified in USVI are similar to other outbreaks of the disease, a lower proportion of acute fever and joint pain was found to be attributable to chikungunya virus.

Flanders virus (FLAV; family Rhabdoviridae) is a mosquito-borne hapavirus with no known pathology that is frequently isolated during arbovirus surveillance programs. Here, we document the presence of FLAV in Culex tarsalis mosquitoes and a Canada goose (Branta canadensis) collected in western North America, outside of the currently recognized range of FLAV. Until now, FLAV-like viruses detected in the western United States were assumed to be Hart Park virus (HPV, family Rhabdoviridae), a closely related congener. A re-examination of archived viral isolates revealed that FLAV was circulating in California as early as 1963. FLAV also was isolated in Nebraska, Colorado, South Dakota, North Dakota, and Saskatchewan, Canada. Phylogenetic analysis of the U1 pseudogene for 117 taxa and eight nuclear genes for 15 taxa demonstrated no distinct clustering between western FLAV isolates. Assuming the range of FLAV has been expanding west, these results indicate that FLAV likely spread west following multiple invasion events. However, it remains to be determined if the detection of FLAV in western North America is due to expansion or is a result of enhanced arbovirus surveillance or diagnostic techniques. Currently, the impact of FLAV infection remains unknown.