Background: In New York State (NYS) invasive group A Streptococcus (iGAS) is a reportable disease. Necrotizing fasciitis (NF) and streptococcal toxic shock syndrome (STSS) are severe presentations of iGAS, associated with significant morbidity and mortality. However, these syndromes are not effectively captured through passive laboratory reliant surveillance systems, making it difficult to obtain accurate estimates.
Methods: Through the Emerging Infections Program collaboration between CDC and ten state health departments and academic partners, NYS Active Bacterial Core surveillance (ABCs) conducts active population-based surveillance for iGAS in 15 counties (pop 2.1 million). iGAS is defined as isolation of GAS from a normally sterile site, or from a wound specimen of a patient with NF or STSS. In contrast to passive surveillance, iGAS cases in ABCs counties receive extensive medical chart review to establish case classification as STSS or NF. To assess completeness of reporting of iGAS cases with NF and/or STSS, we compared incidence between 2007 and 2016 in ABCs counties to counties in the rest of the state (ROS; pop. 9.1 million) excluding NYC.
Results: Between 2007 to 2016, iGAS incidence rates increased by 46% and 53% in ABCs and ROS counties respectively, with consistently higher incidence in the ABCs catchment area (Figure 1). There are substantially lower proportions of iGAS cases with NF and STSS in ROS compared to ABCs counties (Figure 2). Among all iGAS cases, NF and STSS rates in ABCs compared to ROS counties are over four (9.2% and 2.2%) and eight times higher (10.6% and 1.3%) respectively. An estimated additional 376 cases of NF and/or STSS among iGAS cases (418% of reported) would be expected in ROS if rates of NF and/or STSS reported in ABCs counties are applied (Figure 3).
Conclusion: Based on ABCs data, NF and STSS among iGAS cases represent a significant disease burden in contrast to substantially lower rates in the ROS. These data demonstrate the limitations of using passive surveillance systems, particularly when clinical information is essential for case classification in addition to lab-based data. These data show the critical importance of active surveillance, such as the ABCs, which can be used to provide more accurate national estimates.
J. V. Rowlands,
D. S. Blog, None
S. M. Zansky, None