Estimating the Burden of Pandemic Infectious Disease: The Case of the Second Wave of Pandemic Influenza H1N1 in Forsyth County, North Carolina.

BACKGROUND: Understanding the burden of influenza A(H1N1)pdm09 virus during the second wave of 2009-2010 is important for future pandemic planning. METHODS: Persons who presented to the emergency department (ED) or were hospitalized with fever and/or acute respiratory symptoms at the academic medical center in Forsyth County, North Carolina were prospectively enrolled and underwent nasal/throat swab testing for influenza A(H1N1)pdm09. Laboratory-confirmed cases of influenza A(H1N1)pdm09 virus identified through active surveillance were compared by capture-recapture analysis to those identified through independent, passive surveillance (physician-ordered influenza testing). This approach estimated the number of total cases, including those not captured by either surveillance method. A second analysis estimated the total number of influenza A(H1N1)pdm09 cases by multiplying weekly influenza percentages determined via active surveillance by weekly counts of influenza-associated discharge diagnoses from administrative data. Market share adjustments were used to estimate influenza A(H1N1)pdm09 virus ED visits or hospitalizations per 1,000 residents. RESULTS: Capture-recapture analysis estimated that 753 residents (95% confidence interval [CI], 424-2,735) with influenza A(H1N1)pdm09 virus were seen in the academic medical center from September 2009 through mid-April 2010; this result yielded an estimated 4.7 (95% CI, 2.6-16.9) influenza A(H1N1)pdm09 virus ED visits or hospitalizations per 1,000 residents. Similarly, 708 visits were estimated using weekly influenza percentages and influenza-associated discharge diagnoses, yielding an estimated 4.4 influenza A(H1N1)pdm09 virus ED visits or hospitalizations per 1,000 residents. CONCLUSION: This study demonstrates that the burden of influenza A(H1N1)pdm09 virus in ED and inpatient settings by capture-recapture analysis was 4-5 per 1,000 residents; this rate was approximately 8-fold higher than that detected by physician-ordered influenza testing.

Verifying influenza and pneumococcal immunization status of children in 2009-2010 from primary care practice records and from the North Carolina Immunization Registry.

BACKGROUND: The North Carolina Immunization Registry (NCIR) has been available since 2004. We sought to measure its utilization among practices that provide primary care for children who are enrolled in a prospective influenza surveillance study. METHODS: This study included children aged 0.5-17 years who presented with fever or acute respiratory symptoms to an emergency department or inpatient setting in Winston-Salem, North Carolina, from September 1, 2009, through May 19, 2010. Study team members verified influenza and pneumococcal immunization status by requesting records from each child's primary care practice and by independently reviewing the NCIR. We assessed agreement of nonregistry immunization medical records with NCIR data using the kappa statistic. RESULTS: Fifty-six practices confirmed the immunization status of 292 study-enrolled children. For most children (238/292, 82%), practices verified the child's immunizations by providing a copy of the NCIR record. For 54 children whose practices verified their immunizations by providing practice records alone, agreement with the NCIR by the kappa statistic was 0.6-0.7 for seasonal and monovalent H1N1 influenza vaccines and 0.8-0.9 for pneumococcal conjugate and polysaccharide vaccines. A total of 221 (98%) of 226 enrolled children younger than 6 years of age had 2 or more immunizations documented in the NCIR. LIMITATIONS: NCIR usage may vary in other regions of North Carolina. CONCLUSION: More than 95% of children younger than 6 years of age had 2 or more immunizations documented in the NCIR; thus, the Centers for Disease Control and Prevention 2010 goal for immunization information systems was met in this population. We found substantial agreement between practice records and the NCIR for influenza and pneumococcal immunizations in children.

Relative timing of influenza disease by age group.

A detailed understanding of influenza movement in communities during yearly epidemics is needed to inform improved influenza control programs. We sought to determine the relative timing of influenza presentation and symptom onset by age group and influenza strain. Prospective, laboratory-confirmed surveillance was performed over three moderate influenza seasons in emergency departments and inpatient settings of both medical centers in Winston-Salem, NC. Influenza disease presented first in school age children through community epidemics of influenza A(H1N1)pdm09 and influenza B, and first in persons 5-49 years old for influenza A(H3N2). This finding indicates that influenza prevention in persons 5-49 years of age may be particularly important in influenza epidemic control.

Evaluation of the limit of detection of the BD Veritor™ system flu A+B test and two rapid influenza detection tests for influenza virus.

We evaluated the limits of detection of 3 rapid influenza diagnostic tests-BD Veritor™ System for Flu A+B, Binax NOW® Influenza A+B, and QuickVue® Influenza-for influenza strains circulating in 2010-2012. Limits of detection varied by influenza strain, with Veritor™ Flu A+B test showing the lowest limit of detection for all strains.

Assessment of parental report for 2009-2010 seasonal and monovalent H1N1 influenza vaccines among children in the emergency department or hospital.

OBJECTIVE: To assess the validity of parental report for seasonal and monovalent H1N1 influenza vaccinations among children 6 months to <18 years who were recommended to receive both vaccines in 2009-2010. METHODS: Children with fever or respiratory symptoms were prospectively enrolled in both emergency departments in Forsyth County, North Carolina, and the only pediatric hospital in the region. Enrollment occurred from September 1, 2009, through April 12, 2010, during the H1N1 influenza pandemic. A parental questionnaire was administered by trained interviewers to ascertain the status of seasonal and monovalent H1N1 influenza vaccines. Parental report was compared with that documented in the medical record and/or the North Carolina immunization registry. RESULTS: Among 297 enrolled children 6 months to <18 years of age, 174 (59%) were 6 months to 4 years, 67 (23%) were 5-8 years, and 56 (19%) were 9 to <18 years. Parents reported that 140 (47%) children had received ≥1 dose of 2009-2010 influenza vaccine-128 (43%) for seasonal vaccine and 63 (21%) for H1N1 vaccine. Confirmed vaccination data indicated that 156 (53%) children had received ≥1 dose of any 2009-2010 vaccine-120 (40%) for seasonal vaccine and 53 (18%) for H1N1 vaccine. Parental report of any seasonal influenza vaccination was 92% sensitive and 86% specific and had a kappa of 0.76. Parental report for any H1N1 influenza vaccination was 88% sensitive and 92% specific with a kappa of 0.71. CONCLUSIONS: Parental report of 2009-2010 seasonal and monovalent H1N1 influenza vaccinations was sensitive and specific and had reasonable agreement with the medical record and/or immunization registry.