Comparison of nasal and nasopharyngeal swabs for influenza detection in adults.

OBJECTIVE: Examine differences in the detection of influenza by specimen and test type using paired nasal and nasopharyngeal swabs. DESIGN: Prospective study SETTING: Enrollment took place between January and March 2007 in a central Wisconsin population. PARTICIPANTS: Adult patients were screened and enrolled by trained research coordinators following medical encounters for acute respiratory illnesses of <10 days duration. METHODS: Paired nasal and nasopharyngeal swabs were collected from consenting patients and tested by both real-time reverse transcriptase polymerase chain reaction (rRT-PCR) and viral culture. A composite measure of positivity was used as the gold standard; cases included any positive result by rRT-PCR or viral culture from either specimen type. RESULTS: Paired samples were collected from 240 adults; 33 (14%) individuals tested positive for influenza by rRT-PCR. Using rRT-PCR, the sensitivity of the nasal swab was 89% (95% CI, 78%-99%) and the sensitivity of the nasopharyngeal swab was 94% (95% CI, 87%-100%), compared to a composite gold standard. CONCLUSION: Test sensitivity did not vary significantly by swab type when using a highly sensitive molecular diagnostic test, but power was limited to detect modest differences.

Evolution of northeastern and midwestern Borrelia burgdorferi, United States.

The per capita incidence of human Lyme disease in the northeastern United States is more than twice that in the Midwest. However, the prevalence of Borrelia burgdorferi, the bacterium that causes Lyme disease, in the tick vector is nearly identical in the 2 regions. The disparity in human Lyme disease incidence may result from a disparity in the human invasiveness of the bacteria in the Northeast and Midwest caused by fundamentally different evolutionary histories. B. burgdorferi populations in the Northeast and Midwest are geographically isolated, enabling evolutionary divergence in human invasiveness. However, we found that B. burgdorferi populations in the Northeast and Midwest shared a recent common ancestor, which suggests that substantial evolutionary divergence in human invasiveness has not occurred. We propose that differences in either animal ecology or human behavior are the root cause of the differences in human incidence between the 2 regions.

Performance of Binax NOW Flu A and B and direct fluorescent assay in comparison with a composite of viral culture or reverse transcription polymerase chain reaction for detection of influenza infection during the 2006 to 2007 season.

The Binax NOW Flu A and Flu B (Binax NOW), direct fluorescent assay (DFA), and viral culture were evaluated and compared with a composite of viral culture or reverse transcription polymerase chain reaction (RT-PCR). Participants with medically attended acute respiratory illness were identified through active surveillance during the 2006 to 2007 season, and consenting individuals (n=932) were tested for influenza by culture and RT-PCR. Physicians ordered a rapid antigen test (Binax NOW [n=73] or DFA [n=70]) according to their clinical judgment. The Binax NOW detected 11 of 18 influenza infections (sensitivity, 61%; 95% confidence interval [CI], 36-83%), whereas DFA detected 17 of 21 influenza infections (sensitivity 81%, 95% CI, 58-95%). Compared with culture/RT-PCR, specificity of both Binax NOW and DFA was 100%. During the 2006 to 2007 influenza season, DFA and Binax NOW demonstrated high specificity but failed to identify a substantial proportion of influenza infections.

Performance of Directigen flu A+B enzyme immunoassay and direct fluorescent assay for detection of influenza infection during the 2004-2005 season.

Early diagnosis of influenza infection is needed to optimize the benefit of prescribing antiviral drugs. However, the accuracy of rapid tests is highly variable. This study evaluated the performance of Directigen flu A+B enzyme immunoassay (EIA) and direct fluorescent assay (DFA) during the 2004-2005 influenza season. Participants with medically attended acute respiratory illness were identified through an active surveillance. Consenting patients (n=818) were enrolled and cultured for influenza. Physicians ordered a rapid antigen test (EIA or DFA) according to their clinical judgment. Physicians ordered rapid tests with EIA (n=109), DFA (n=86), or both (n=9) in 204 patients with acute respiratory illness who were also cultured for influenza. The EIA detected 18 of 43 influenza infections (sensitivity, 42%; 95% confidence interval [CI], 28-57%), whereas DFA detected 26 of 38 influenza infections (sensitivity, 68%; 95% CI, 53-81%). Compared with culture, specificity of both EIA and DFA was 96%. During the 2004-2005 influenza season, both the EIA and DFA had low sensitivity and failed to detect influenza in many patients.

Multilocus sequence typing of Borrelia burgdorferi suggests existence of lineages with differential pathogenic properties in humans.

The clinical manifestations of Lyme disease, caused by Borrelia burgdorferi, vary considerably in different patients, possibly due to infection by strains with varying pathogenicity. Both rRNA intergenic spacer and ospC typing methods have proven to be useful tools for categorizing B. burgdorferi strains that vary in their tendency to disseminate in humans. Neither method, however, is suitable for inferring intraspecific relationships among strains that are important for understanding the evolution of pathogenicity and the geographic spread of disease. In this study, multilocus sequence typing (MLST) was employed to investigate the population structure of B. burgdorferi recovered from human Lyme disease patients. A total of 146 clinical isolates from patients in New York and Wisconsin were divided into 53 sequence types (STs). A goeBURST analysis, that also included previously published STs from the northeastern and upper Midwestern US and adjoining areas of Canada, identified 11 major and 3 minor clonal complexes, as well as 14 singletons. The data revealed that patients from New York and Wisconsin were infected with two distinct, but genetically and phylogenetically closely related, populations of B. burgdorferi. Importantly, the data suggest the existence of B. burgdorferi lineages with differential capabilities for dissemination in humans. Interestingly, the data also indicate that MLST is better able to predict the outcome of localized or disseminated infection than is ospC typing.

Comparison of clinical features and outcomes of medically attended influenza A and influenza B in a defined population over four seasons: 2004-2005 through 2007-2008.

BACKGROUND: There are few prospectively collected data comparing illnesses caused by different subtypes of influenza. We compared the clinical presentation and outcomes of subjects with primarily outpatient-attended influenza A and B infections during four consecutive influenza seasons (2004-2005 through 2007-2008). METHODS: Patients were prospectively enrolled and tested for influenza following an encounter for acute respiratory illness. Influenza infections were confirmed by culture or reverse transcription polymerase chain reaction; subtype was determined for a sample of influenza A isolates each season. Clinical characteristics of influenza A and B infections were compared across and within individual seasons. RESULTS: We identified 901 cases of influenza A and 284 cases of influenza B; 98% of cases were identified through an outpatient medical encounter. Thirty-six percent of patients with each strain had received seasonal influenza vaccine prior to illness onset. There were no consistent differences in symptoms associated with influenza A and B. Influenza A infection was associated with earlier care seeking compared with influenza B during the 2005-2006 and 2007-2008 seasons, when H3N2 was the dominant type A virus, and in a combined analysis that included all seasons. Twenty-six (2·2%) of 1185 cases were diagnosed with radiographically confirmed pneumonia, and 59 (5%) of 1185 patients were hospitalized within 30 days of illness onset. CONCLUSIONS: Over four influenza seasons, aside from shorter intervals from illness onset to clinical encounter for infections with the A(H3N2) subtype, clinical symptoms and outcomes were similar for patients with predominantly outpatient-attended influenza A and B infections.

Prospective study of avian influenza infection in backyard poultry flocks and flock handlers in Wisconsin.

BACKGROUND: The continuing epizootic of H5N1 avian influenza (AI) in Asia and subsequent zoonotic transmission has led to heightened concerns about a pandemic and the demand for improved surveillance of poultry in all sectors, including backyard poultry. We conducted a 15-month prospective study to determine the prevalence of AI in backyard poultry and extent of transmission to flock handlers. METHODS: Starting July 2007, registered poultry owners in six counties in central Wisconsin were mailed invitations to participate; household members with poultry exposure were also invited. Premises with < 1000 birds were eligible. Participants completed a baseline interview to characterize poultry exposures. Illness in flocks and flock handlers was monitored using semimonthly telephone interviews and self-report of acute influenza-like symptoms by flock handlers. Participants provided blood at baseline and at the end of the surveillance period for serology and, if ill, nasopharyngeal, eye, and throat swabs for viral testing. Blood was also collected at baseline from a convenience sample of adult poultry. RESULTS: We enrolled 87 flocks and 128 persons who had regular contact with poultry. Influenza-like symptoms were reported by 77 (65%) persons. Swabs were collected from 53 persons at 88 illness episodes. AI was not isolated, but five persons were positive for human influenza. Twenty-one participants (20%) seroconverted to at least one human influenza strain, but there were no seroconversions to AI. Blood samples from all 717 birds tested were seronegative for influenza. CONCLUSION: Despite limited biosecurity there was no evidence of AI infection in participating backyard flocks or flock handlers.

West Nile virus infection in commercial waterfowl operation, Wisconsin.

A West Nile virus (WNV) outbreak occurred at a commercial waterfowl operation in Wisconsin in 2005. Retrospective analysis of dead and live birds was conducted. WNV was detected by PCR in 84.1% of 88 dead birds; neutralizing antibodies were found in 14 of 30 randomly sampled asymptomatic or recovered birds.

Use of streptogramin growth promoters in poultry and isolation of streptogramin-resistant Enterococcus faecium from humans.

BACKGROUND: Virginiamycin use in poultry selects for Enterococcus faecium with cross-resistance to quinupristin-dalfopristin, a drug for vancomycin-resistant E. faecium in humans. We conducted an epidemiologic study of poultry exposures as risk factors for human carriage of quinupristin-dalfopristin-resistant E. faecium. METHODS: Rectal or fecal samples for E. faecium testing were obtained from 567 newly admitted hospital patients and 100 healthy vegetarians. Participants were interviewed regarding poultry exposure. Retail poultry washes (160 conventional and 26 antibiotic free) were also tested for the presence of E. faecium. Constitutive and inducible quinupristin-dalfopristin resistance were assessed in E. faecium isolates, and resistance genes were identified by polymerase chain reaction. RESULTS: E. faecium was isolated from 105 patients, 65 vegetarians, and 77 conventional and 23 antibiotic-free poultry washes. Constitutive quinupristin-dalfopristin resistance was absent in human E. faecium, but 56% of conventional poultry isolates were quinupristin-dalfopristin resistant. Inducible quinupristin-dalfopristin resistance was more common in samples from patients than in those from vegetarians and in washes of conventional than antibiotic-free poultry. Higher poultry consumption was associated with inducible quinupristin-dalfopristin resistance. vatE was present in 38% of E. faecium isolates from patients and none from vegetarians. Touching raw poultry was associated with the presence of vatE. CONCLUSIONS: Poultry exposure is associated with a quinupristin-dalfopristin resistance gene and inducible quinupristin-dalfopristin resistance in human fecal E. faecium. The continued use of virginiamycin may increase the potential for streptogramin-resistant E. faecium infection in humans.