Hospital admissions syndromic surveillance--Connecticut, October 2001-June 2004

The Connecticut Department of Public Health (CDPH) has continuously monitored daily nonelective hospital admissions through a syndromic surveillance reporting system (HASS) since September 2001. Admission diagnoses are categorized into 11 syndromes including one possible indicator of smallpox, fever with rash, and one possible indicator of influenza and pneumonia.

The objectives are to describe findings from systematic investigation of individual admissions attributed to fever and rash and to determine the utility of monitoring pneumonia admissions as an indicator of severe influenza activity during the 2003-04 influenza season.

The incidence of admissions for fever and rash illness was determined for a 12-month period, and results of clinical discharge diagnoses were tabulated. Excess admissions for pneumonia by week during the influenza seasons beginning 2001-03 were determined and compared. Trends in admissions from the 2003-04 season were compared with trends from laboratory and sentinel physician surveillance.

A total of 57 admissions for fever and rash illness were reported from 32 acute-care hospitals and verified for an incidence of 1.7 per 100,000 population. Specific clinical diagnoses were made for 29. Many were compatible with the initial clinical presentation of smallpox. Excess admissions for pneumonia during the 2003-04 season occurred concurrently with sharp increases in positive laboratory reports and percentages of visits to physician's offices attributed to influenza-like illness. The 2003-04 influenza season had many more excess admissions than the 2001-02 and 2002-03 seasons.

HASS is a useful surveillance tool for rapid detection of sentinel cases of smallpox. Monitoring excess pneumonia admissions during the influenza season appears to be an effective and specific method for determining levels of influenza activity and for quantification of influenza-related morbidity and impact on the hospital system.