Syndromic Surveillance as a Tool for Case-Based Varicella Reporting in Georgia, 2016-2019

Abstract

Objectives: Syndromic surveillance can be used to enhance notifiable disease case-based surveillance. We analyzed features of varicella reported in Georgia to evaluate case detection through syndromic surveillance and to compare varicella reported through syndromic surveillance with varicella reported from all other sources.

Methods: Syndromic surveillance was incorporated into case-based varicella surveillance by the Georgia Department of Public Health (GDPH) in May 2016. A cross-sectional study design evaluated syndromic and nonsyndromic varicella reported to GDPH from May 1, 2016, through December 31, 2019. Varicella was reported by nonsyndromic sources including health care providers, schools, and laboratories. We identified syndromic varicella cases from urgent care and emergency department visit data with discharge diagnoses containing the terms "varicella" or "chickenpox."

Results: Syndromic notifications accounted for 589 of 2665 (22.1%) suspected varicella reports investigated by GDPH. The positive predictive value was 33.1% for syndromic notifications and 31.3% for nonsyndromic notifications. Mean days from rash onset to GDPH notification was 3.2 days fewer (P < .001) among patients identified through syndromic notification than among patients identified through nonsyndromic notification. The odds of varicella identified by syndromic notification being outbreak-associated were 0.18 (95% CI, 0.09-0.36) times those of varicella identified through nonsyndromic notification.

Practice implications: Syndromic notifications were an effective, timely means for varicella case detection. Syndromic patients were significantly less likely than nonsyndromic patients to be outbreak-associated, possibly because of early detection. Syndromic surveillance enhanced case-based reporting for varicella in Georgia and was a useful tool to improve notifiable disease surveillance.

Keywords: epidemiology; infectious disease surveillance; syndromic surveillance; vaccine-preventable diseases; varicella.

Figure 1

Evaluation of varicella reporting sources in Georgia, May 1, 2016, through December 31, 2019. Electronic laboratory reporting was implemented for varicella in January 2016. Suspected varicella reports designated as “not a case” might include reports of patients with addresses outside Georgia. The health department category includes state or local health departments; these reports might include cases reported by external partners through faxed laboratory reports or telephone calls, in addition to cases diagnosed at health departments. The correctional facility category includes federal prisons, federal detention centers, US Immigration and Customs Enforcement processing centers, and state and county jails.

Figure 2

Varicella case detection through syndromic surveillance notifications, Georgia, May 1, 2016, through December 31, 2019. Epidemiologically linked cases are cases in which patients with a known exposure occur within 1 incubation period (21 days) of one another. A household cluster is defined as ≥3 epidemiologically linked patients with varicella in the same household (not including residential settings, such as prisons and dormitories). An outbreak is defined as ≥3 epidemiologically linked patients with varicella in the same setting, with transmission outside a household. Abbreviation: GDPH, Georgia Department of Public Health.