Preliminary results of 2009 pandemic influenza surveillance in the United States using the Aggregate Hospitalization and Death Reporting Activity

System for rapid assessment of pneumonia and influenza-related mortality-Ohio, 2009-2010

Rapid mortality surveillance is critical for state emergency preparedness. To enhance timeliness during the 2009-2010 influenza A H1N1 pandemic, the Ohio Department of Health activated a drop-down menu within Ohio's Electronic Death Registration System for reporting of pneumonia- or influenza-related deaths approximately 5 days postmortem. We used International Classification of Diseases-Tenth Revision (ICD-10) codes, available 2-3 months postmortem as the standard, and assessed their agreement with drop-down-menu codes for pneumonia- or influenza-related deaths. Among 56 660 Ohio deaths during September 2009-March 2010, agreement was 97.9% for pneumonia (κ = 0.85) and 99.9% for influenza (κ = 0.79). Sensitivity was 80.2% for pneumonia and 73.9% for influenza. Drop-down menu coding enhanced timeliness while maintaining high agreement with ICD-10 codes.

Mortality burden of the 2009-10 influenza pandemic in the United States: improving the timeliness of influenza severity estimates using inpatient mortality records

BACKGROUND

Delays in the release of national vital statistics hinder timely assessment of influenza severity, especially during pandemics. Inpatient mortality records could provide timelier estimates of influenza-associated mortality.

METHODS

We compiled weekly age-specific deaths for various causes from US State Inpatient Databases (1990-2010) and national vital statistics (1990-2009). We calculated influenza-attributable excess deaths by season based on Poisson regression models driven by indicators of respiratory virus activity, seasonality, and temporal trends.

RESULTS

Extrapolations of excess mortality from inpatient data fell within 11% and 17% of vital statistics estimates for pandemic and seasonal influenza, respectively, with high year-to-year correlation (Spearman's rho = 0.87-0.90, P < 0.001, n = 19). We attribute 14,800 excess respiratory and cardiac deaths (95% CI: 10,000-19,650) to pandemic influenza activity during April 2009-April 2010, 79% of which occurred in people under 65 years.

CONCLUSIONS

Modeling inpatient mortality records provides useful estimates of influenza severity in advance of national vital statistics release, capturing both the magnitude and the age distribution of pandemic and epidemic deaths. We provide the first age- and cause-specific estimates of the 2009 pandemic mortality burden using traditional 'excess mortality' methods, confirming the unusual burden of this virus in young populations. Our inpatient-based approach could help monitor mortality trends in other infectious diseases.

Age- and sex-specific mortality associated with the 1918-1919 influenza pandemic in Kentucky

Background. The reasons for the unusual age-specific mortality patterns of the 1918–1919 influenza pandemic remain unknown. Here we characterize pandemic-related mortality by single year of age in a unique statewide Kentucky data set and explore breakpoints in the age curves.

Methods. Individual death certificates from Kentucky during 1911–1919 were abstracted by medically trained personnel. Pandemic-associated excess mortality rates were calculated by subtracting observed rates during pandemic months from rates in previous years, separately for each single year of age and by sex.

Results. The age profile of excess mortality risk in fall 1918 was characterized by a maximum among infants, a minimum at ages 9–10 years, a maximum at ages 24–26 years, and a second minimum at ages 56–59 years. The excess mortality risk in young adults had been greatly attenuated by winter 1919. The age breakpoints of mortality risk did not differ between males and females.

Conclusions. The observed mortality breakpoints in male and female cohorts born during 1859–1862, 1892–1894, and 1908–1909 did not coincide with known dates of historical pandemics. The atypical age mortality patterns of the 1918–1919 pandemic cannot be explained by military crowding, war-related factors, or prior immunity alone and likely result from a combination of unknown factors.

Epidemiology of influenza A (H1N1)pdm09-associated deaths in the United States, September-October 2009

BACKGROUND

From April to July 2009, the United States experienced a wave of influenza A (H1N1)pdm09 virus (H1N1pdm09) infection. The majority of the deaths during that period occurred in persons <65 years of age with underlying medical conditions.

OBJECTIVE

To describe the epidemiology of H1N1pdm09-associated deaths in the US during the fall of 2009.

METHODS

We collected demographic, medical history, and cause of death information on a nationally representative, stratified random sample of 323 H1N1pdm09-associated deaths that occurred during September 1-October 31, 2009.

RESULTS

Data were available for 302/323 (93%) deaths. Most cases (74%) were 18-64 years of age and had ≥ 1 underlying medical condition (72%). Among cases aged <18 years, 16/43 (37%) had a chronic lung disease, and 15/43 (35%) a neurological disorder; among cases aged ≥ 18 years, 94/254 (37%) had a chronic lung disease and 84/254 (33%) had a metabolic disorder. The median number of days between symptom onset and death was six among children (range, 1-48) and 12 among adults (range, 0-109). Influenza antiviral agents were prescribed for 187/268 (70%) of cases, but only 48/153 (31%) received treatment within 2 days of illness onset.

CONCLUSIONS

The characteristics of H1N1pdm09 deaths identified during the fall of 2009 were similar to those occurring April-July 2009. While most cases had conditions that were known to increase the risk for severe outcomes and were recommended to receive antiviral therapy, a minority of cases received antivirals early in the course of illness.

H5N1 avian influenza in children

BACKGROUND

Avian influenza continues to pose a threat to humans and maintains the potential for greater transmissibility. Understanding the clinical presentation and prognosis in children will help guide effective diagnosis and treatment.

METHODS

A global patient registry was created to enable systematic collection of clinical, exposure, treatment, and outcomes data on confirmed cases of H5N1. Bivariate and multivariate statistical tools were used to describe clinical presentation and evaluate factors prognostic of survival.

RESULTS

Data were available from 13 countries on 193 children <18 years who were confirmed as having been infected with H5N1; 35.2% of cases were from Egypt. The case fatality rate (CFR) for children was 48.7%, with Egypt having a very low pediatric CFR. Overall, children aged ≤5 years had the lowest CFR and were brought to hospitals more quickly and treated sooner than older children. Children who presented for medical care with a complaint of rhinorrhea had a 76% reduction in the likelihood of death compared with those who presented without rhinorrhea, even after statistical adjustment for age, having been infected in Egypt, and oseltamivir treatment (P = .02). Delayed initiation of treatment with oseltamivir increases the likelihood of death, with an overall 75% increase in the adjusted odds ratio for death for each day of delay.

CONCLUSIONS

The presence of rhinorrhea appears to indicate a better prognosis for children with H5N1, with most patients surviving regardless of age, country, or treatment. For individuals treated with oseltamivir, early initiation of treatment substantially enhances the chance of survival.