Issue 22 - Influenza Surveillance Improved with Syndromic Surveillance

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Influenza Surveillance Improved with Syndromic Surveillance
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Influenza surveillance in the past has focused on a three-pronged approach:
1) Passive systems (expecting health practitioners to report the number of patients seen with flu-like illness),
2) Active systems (sentinel medical practices or clinics are called by health department officials on a regular basis to collect numbers of cases), and
3) Laboratory surveillance (labs report positive tests, and identify viral strains).

Modern syndromic surveillance has the potential to provide these data in a much more timely and efficient fashion. Two recent articles from different parts of the country confirm that syndromic surveillance accomplishes just that.

In the March issue of Government Technology magazine, Ed Carubis (Associate Commissioner of the NYC Department of Health and Mental Hygiene) says regarding syndromic surveillance, “We predicted the flu outbreak two weeks in advance of traditional surveillance methods.”(1) In a recent e-newsletter article, Brian Labus MPH, from the Clark County Health District in Las Vegas confirms the same result: “Syndromic Surveillance identified the start of the (2003-2004) influenza season two weeks before it was identified through sentinel-provider surveillance... early identification was instrumental in providing an effective response.”(2)

The NYC DHMH uses a variety of data sources in their syndromic surveillance system. They include emergency room complaint data from 40 different hospitals, 911 calls, and pharmacy sales. These data are merged into a common format for analysis by a group of epidemiologists. “The epidemiologists form hypotheses about what may be occurring and determine the information needed to confirm their hypothesis. Then they interview patients to determine exactly what they are dealing with”.(1) In the case of influenza, the two week head-start was critical, because it allowed them to notify the medical community and encourage people at risk to get vaccinated.

At the Clark County Health District (CCHD) in Las Vegas, syndromic surveillance is based on “complaint data from one major hospital system, which includes all hospital services, outpatient clinics, emergency rooms and urgent care centers.”(2) Data is transmitted and analyzed daily using a custom-designed system. Epidemiologists review all surveillance reports.

Syndromic surveillance for influenza in Clark County yielded a number of benefits. The medical community was notified and encouraged to test for influenza. Press releases were sent encouraging immunization; daily reports of case counts and deaths were sent (which pre-empted the usual overwhelming individual phone calls). They were able to monitor the community-wide progress of the disease and identify the peak. It also gave them insight into the range of patient symptoms, such as vomiting in children.

While syndromic surveillance systems were intended to detect possible bioterrorism, their most valuable use to date has been to detect naturally occurring outbreaks. Both purposes are achieved by capturing data early enough to “control, mitigate or respond to an event”.(1)

(1) http://www.govtech.net/magazine/story.php?id=89565
(2) http://bt.naccho.org/E-newsletter-archive/SS-Influenza.htm

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