Page 103 - Timeliness of Infectious Disease Notification & Response Systems - Corien Swaan

Quantifying reporting timeliness to improve outbreak control 101
PIR2<1). Thin dashed lines show reporting delay medians bringing diseases under the lower outbreak control condition (R2 x PIR2<1). Symbols indicate PIR2 evaluated with current reporting delay data. HepA, hepatitis A; hepB, hepatitis B; PIR2, expected pro- portion of new infections caused by seondary cases before index case is notified; R, reproduction number.
Room for Improving Reporting Timeliness
Interventions applied only to index cases are rather inefficient, even with the swiftest reporting. Figure 6 shows that even when a case is (unrealistically) re- ported on the same day of symptom onset (median = 0), PIR2 values are abo- ve their respective outbreak control limit for 5 of the 6 studied diseases. This finding is because of the proportion of expected secondary infections an index case produces while asymptomatic (6). The exception is shigellosis, but for this diseases already a median reporting delay of 1 day would be too late for imple- menting outbreak control. In general, only short reporting delays of ⁓3 days would enable substantial reduction of PIR1 for the 6 diseases. Moreover, with current reporting delays the largest PIR1 reduction ratio achieved by reducing current delays by 1 day is 2.6%, for hepatitis A (Table 2). However, for some diseases, the efficiency of applying interventions also to traced contacts can be substantially increased by reducing reporting delays. Relevant results are sum- marised in Table 2.
Figure 7 shows that for sufficiently short reporting delay medians, the up- per outbreak control condition could eventually be satisfied for all 6 diseases. If the median reporting delay for hepatitis A were 8 days, the lower, more restric- tive, outbreak control condition could be satisfied. Outbreak control for measles and mumps would need reporting delay medians of 2 and 3 days, respectively. For hepatitis B and shigellosis, reporting would need to be almost instantane- ous (1-day delay); for pertussis, the lower outbreak control condition could not be satisfied even if reported the same day as symptom onset. The PIR2 reduc- tion ratio is high for hepatitis A, measles and mumps, indicating that significant improvement can be achieved with reporting delay reductions of 1(or a few) days. However, little improvement is expected with a small reduction of repor- ting delays for hepatitis B, pertussis and shigellosis. Table 2 shows that with underreporting >30%, outbreak control for all 6 diseases is not possible. Table 2 also shows that only for hepatitis A and for hepatitis B would the immunisation coverage needed to achieve outbreak control be substantially reduced, because of individually targeted interventions with the current reporting speed.
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