Chapter 12 Infectious Disease Surveillance
12.1 Overview and Learning Objectives
In this module, we will take a look at surveillance of different infectious diseases.
The learning objectives for this chapter are:
- Understand surveillance
12.2 Introduction
To be able to implement successful interventions, we first need to know what is actually happening. Once we implemented a control strategy, we also want to know how it works. For both of those goals, good surveillance is key.
12.3 Goals of Surveillance
- Identify new emerging diseases as quickly as possible
12.4 Types of Surveillance
Active and passive
Medical/clinical and sequence
Ongoing or ad-hoc
12.5 Problems with surveillance
Knowing numerator and denominator. Bias due to getting more severe cases. Behavior change during an outbreak.
12.5.0.1 Biased Surveillance - an example
During the early days of the 2009 H1N1 influenza pandemic, the numbers on cases and deaths suggested that this strain of influenza might have a higher than normal case fatality ratio (the often used term case fatality rate is a bad label as this is not a rate). Once more and better data became available. It was realized that many infections initially did not get reported, and adjusting for those it became clear that the ratio of deaths to infected was thankfully not much different from seasonal influenza.
12.6 Summary and Cartoon
A comprehensive, ‘always on’ surveillance for infectious diseases would be ideal.