Surveillance & Epidemiologic Investigation Flashcards

An Infection Preventionist (IP) is reviewing the facility's Central Line-Associated Bloodstream Infection (CLABSI) data. The report shows a Standardized Infection Ratio (SIR) of 1.5 for the last quarter. How should the IP interpret this finding?

Answer: The facility had 50% more infections than predicted.

A Standardized Infection Ratio (SIR) greater than 1.0 indicates that more healthcare-associated infections (HAIs) were observed than were predicted based on a national baseline. An SIR of 1.5 means the facility observed 50% more infections than predicted. An SIR less than 1.0 would indicate fewer infections than predicted, and an SIR of 1.0 means the observed number matched the predicted number. [5, 8, 10]

During an investigation of a gastroenteritis outbreak in a long-term care facility, the epidemiologic curve shows a sharp increase in cases over a two-day period, followed by a rapid decline. This pattern is most characteristic of which type of outbreak?

Answer: Point source

A point source outbreak occurs when people are exposed to the same source over a brief period, such as a single meal. The resulting epidemic curve has a rapid rise in cases, a distinct peak, and a gradual decline, with most cases falling within one incubation period. Propagated source outbreaks show progressively taller peaks, continuous source outbreaks have a plateau, and intermittent source outbreaks have irregular peaks. [2, 26, 28]

Which of the following is the primary advantage of active surveillance over passive surveillance for healthcare-associated infections?

Answer: It is more likely to identify all cases and provide more accurate data.

Active surveillance, where trained personnel proactively search for cases using various data sources, is more comprehensive and tends to yield more accurate and complete data than passive surveillance, which relies on others to report cases. While more resource-intensive, active surveillance is less likely to miss cases. [16, 20, 29]

An Infection Preventionist is investigating a potential foodborne illness outbreak following a staff potluck. Of the 75 employees who ate the potato salad, 15 developed symptoms of gastroenteritis. What is the attack rate for the potato salad?

Answer: 20%

The attack rate is calculated by dividing the number of new cases of a disease by the number of people at risk for the disease, then multiplying by 100 to express it as a percentage. In this scenario, the calculation is (15 ill people / 75 people who ate the food) * 100 = 20%. [1, 3, 14]

An IP is called to a nursing unit where three patients have developed C. difficile infection within the last 48 hours. What is the most critical first step in this epidemiologic investigation?

Answer: Establish a case definition to identify all potential cases systematically.

A crucial early step in any outbreak investigation is to establish a clear and consistent case definition. This set of criteria for person, place, time, and clinical features ensures that all potential cases are identified systematically, which is essential before implementing widespread control measures or forming a specific hypothesis. [4, 6, 18]

When designing a surveillance plan for a healthcare facility, which of the following is the most important initial step?

Answer: Conducting a risk assessment of the patient population and services provided.

The design of a surveillance system should begin with a comprehensive risk assessment. This process involves evaluating the population served, the types of care and services provided, and analyzing existing data to identify the facility's specific risks for infection. The goals and objectives of the surveillance plan are then based on the findings of this assessment. [19, 21, 25]