Page 105 - Timeliness of Infectious Disease Notification & Response Systems - Corien Swaan

Quantifying reporting timeliness to improve outbreak control 103
ses would be worthwhile because doing so would increase the effectiveness of interventions applied to secondary cases. However, using resources to reduce reporting delays for hepatitis B, pertussis and shigellosis would not be worthw- hile for outbreak control purposes because a substantial increase of prevented infections could be achieved only with extreme reporting delay reductions (per- tussis and shigellosis) or not at all (hepatitis B).
In the context of transmission of infection, calculations of PIR1 and PIR2 provide an objective measure for the timeliness of reporting and interventions. We focused on outbreak control as a goal (reducing reproduction number to <1), but the method we described can also be used to assess reporting delays with another goal in mind. For example, for an extremely serious disease, the goal might be to reduce PIR1 and PIR2 to the smallest acceptable limit.
Maximum limits of underreporting that would allow for any possibility of outbreak control are rather small (Table 2). Therefore, in addition to being time- ly, reporting must also be very complete.
The median is a robust characteristic of a dataset because it is not influen- ced largely by outliers. Therefore, medians have been used in many studies to compare data on factors such as latent periods, serial intervals and notification delays but without taking into account the shape of the distributions (1–3). It is reassuring that we found that calculations of PIR1 and PIR2 mainly depend on medians and not on the standard deviations of reporting delay distributions.
We have quantitatively assessed the outbreak control potential of res- ponses of PHAs on the basis of the timeliness of the current reporting delays of hepatitis A, hepatitis B, measles, mumps, pertussis and shigellosis in the Netherlands. We used the expected proportion of infections caused by index and secondary cases until reported to the local PHA (PIR1 and PIR2). These di- sease-specific quantities provide a powerful tool for setting goals for reporting speeds not only for outbreak control, but also for evaluation of individual-based interventions with other aims, such as partially reducing infections or complete- ly stopping transmission.
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