Page 208 - Timeliness of Infectious Disease Notification & Response Systems - Corien Swaan

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outbreaks up to 2 years earlier, and consequently, earlier source investigation and control measures (50). These findings demonstrate the relevance of timely disease identification in the notification chain, which is incorporated in the out- break control timeframe.
Lastly, this thesis focuses on timeliness as measurable indicator for evalu- ating a surveillance system. However, another important measurable attribute determining the quality of a surveillance system is completeness of case re- porting, i.e. the rate of underreporting of diseases (51). The extent, and there- fore the influence of underreporting in an early warning, varies substantially between diseases. In a review of studies from the United States, Doye et al. demonstrated considerably reduced reporting completeness, ranging from 9-99% (52). Yoo et al. determined a completeness varying between 40% (hem- orrhagic fever with renal syndrome, HFRS) and 80% (shigellosis) in South Korea (10). More recently, van der Maas et al. estimated completeness of reporting rates of notifications of hospitalized cases with pertussis between 17.5% - 62% (53). Nowadays, Electronic Laboratory Reporting systems contribute to more completeness of reporting (54, 55). Besides underreporting, also under-ascer- tainment of infections contributes to the underestimation of all infections in a population, which is the result of not all patients seeking medical consultation and physicians’ omission to recognize the disease and initiate laboratory investi- gation (56). Underestimation rates are related to specific diseases, surveillance systems, reporting procedures and specific demographic groups, which makes it complex to measure. Underreporting has larger consequences in outbreak con- trol than delayed notification or reporting. However, very delayed notification can be considered as under-reporting when secondary cases already have been notified and notification of the index case does not lead to additional control measures.
9.4 Timeframes in a comprehensive and international perspective
Timeframe for timeliness in surveillance and response systems
A timeframe is a period (days, weeks, months) in which an activity is intended to happen. The existing timeframes for surveillance involve legal timeframes for notification and reporting in the Netherlands. These are commonly used inter- nationally, but only refer to the administrative part of the notification and re- porting chain (Figure 1, this thesis). As the aim of notification is threat detection,