A process evaluation of an active surveillance system for hospitalized 2009-2010 H1N1 influenza cases

A process evaluation was conducted to evaluate a newly established active influenza surveillance program that utilized 6 sentinel hospitals to collect epidemiologic information for influenza-like illness admissions. Objectives were to determine whether the new system was implemented successfully and met surveillance objectives, including determination of the proportion of patients with 2009 H1N1 influenza, extent of disease severity, and identifying high-risk groups.

Timeliness and data quality were assessed through analysis of electronic case report form completion and timing of specimen collection and submission to public health laboratories for influenza testing. Simplicity and accessibility of the surveillance system were assessed through a survey of hospital-based surveillance staff.

The median number of days from admission to initial reporting was 5 days. The completeness of core variables was more than 98%, 96.2% for complications, and 92.6% for underlying medical conditions. Among influenza-like illness admissions, 77.8% had a specimen submitted for confirmatory testing. Eighty-nine percent of survey respondents found guidance provided by New York State Department of Health to be helpful and case report forms easy to use.

This project was implemented within a context of limited time and resources. Certain aspects of planning, such as securing necessary staffing at some hospitals, could not be carried out prior to implementation. Resource limitations necessitated controls on the numbers of specimens submitted each week. Some reporting lags were noted because of delays in data entry. Reporting timeframes allowed for timely data summarization for internal decision making. Maintaining frequent contact with sentinel sites promoted report completeness, timeliness, and consistency across sites. These results highlight the value of sentinel surveillance methodology and challenges of rapidly deploying a new active surveillance system for an emergent disease.