Syndromic Surveillance Page

North Dakota Department of Health Syndromic Surveillance Program

In 2004, the North Dakota Department of Health (NDDoH) implemented a syndromic surveillance system to monitor disease trends and detect outbreaks. Chief complaint data is received electronically from eight large hospital emergency departments located in North Dakota’s six largest cities. In addition, data from a nurse advice call center in North Dakota's largest city is received and reviewed daily. One additional hospital emergency department has signed a contract to participate in the program, increasing the data source to include seven of North Dakota’s largest cities and highest populated counties, including over 50 percent of the state’s population (Figure 1).

Figure 1. Map of North Dakota Syndromic Surveillance Sites.

The NDDoH receives daily electronic files and analyzes data using the commercial software RedBatÒ (ICPA, Austin, TX). The chief complaint reported during registration at the emergency room is coded into symptoms, which are then scored into ten syndromes. Table 1 lists the ten syndromes detectable with the RedBatÒ software and possible etiologies commonly associated with each syndrome.

Table 1. RedBat^Ò Disease Syndromes and Possible Etiology.

Gastrointestinal Illness	Cholera, salmonella, shigella; Food poisoning due to: S.aureus, B.cereus, E.coli, ricin toxin, etc.
Hepatitis Illness	Hepatitis A, yellow fever, alflatoxin, many chemical poisonings
Influenza-like Illness	Influenza, RSV, rhinoviruses. Early stages of pulmonary anthrax, plague and tularemia.
Encephalitis	Eastern equine, Venezuelan equine, western equine, West Nile virus
Neuro-Toxic	Botulism, shellfish toxin, chlorinated hydrocarbons, organophosphates, organic mercury, sarin, VX nerve agent, BZ, cyanide
Pulmonary Disease	Pulmonary forms of anthrax, plague, tularemia, glanders, hantavirus and chlorine gas
Rash Illness	Cutaneous anthrax, smallpox, T2 mycotoxins and mustard agents
Sepsis	Crimean-congo, ebola, lass and marburg hemorrhagic fevers
Systemic Disease	Brucellosis, typhoid, bubonic plague, Q fever, rift valley fever, tularemia
Radiation	Exposure to radioactive chemicals, x-rays or other radiation source.

The statistical methods provided by the software include CUSUM and low, medium and high sensitivity moving average calculations. Signals that exceed set thresholds trigger alarms, which can be reported verbally or notified automatically via email. Participating facilities have access to a secure website to view daily reports of the data in their county, region or facility.

Figure 2. How Flags are Determined

	Both CuSum and Moving Average (MA) flags include blue, yellow, orange, and red flags. The probability of an outbreak increases from blue to red. MA thresholds are based on various combinations of the population mean and moving averages of the mean (or median) plus 2 standard deviations. The flags for the MA and user-defined thresholds are determined as follows:

				No significant values reached on Observation Date (Obs. Date)
				Single value reached High Threshold (on Obs.Date)
				Two consecutive values reached High Threshold (on Obs.Date); Single value reached 2 x Threshold (on Obs.Date)
				Three consecutive values reached High Threshold (on Obs.Date); Two consecutive values reached 2 x Threshold (on Obs.Date)
				Three consecutive values reached 2 x Threshold (on Obs.Date); Single value reached 3 x Threshold (on Obs.Date)

	The flags for the CuSum charts are determined as follow:

				All values below 3-sigma line on Observation Date (Obs. Date)
				CuSum #1 crossed the 3-sigma line (on Obs.Date)
				CuSum #2 crossed the 4-sigma line (on Obs.Date)
				CuSum #3 crossed the 5-sigma line (on Obs.Date)
				CuSum #4 crossed the 6-sigma line (on Obs.Date)

Evaluation of the RedBat^Ò syndromic surveillance system has revealed detectable outbreaks by retrospective study as well as evidence for use in year-round influenza surveillance, as a tool in bioterrorism preparedness and SARS planning and analysis of injury data and asthma trends. The RedBat^Ò system will be most effective when augmented with other surveillance activities being implemented by the NDDoH. These include electronic laboratory reporting, geographical information systems (GIS), the health alert network, animal health, ambulance run, poison control data and over-the-counter drug surveillance systems.