Page 93 - Timeliness of Infectious Disease Notification & Response Systems - Corien Swaan

Disease
Hepatitis A Hepatitis B Measles Mumps Pertussis Shigellosis Ф
Serial interval distribution, median days (SD)
27.5 (4) 47.5 (20) 11.6 (2.4) 19.1 (5.4) 16 (13)
5 (3.5)
Symptom onset distribution, median days (SD)
28 (9)
80 (35) 11.5 (2.5) 19.5 (2.3) 9 (2.5) 2.5 (1.5)
Reporting delay distribution, median days (SD)
8.6 (11.9) 14.7 (24.3) 9.0 (12) 9.0 (13.8) 40.8 (24.4) 14.6 (13.8)
Reproduction number, R (range) ¥
3.33 (3-4) 1.75 (1-2.5) 8 (8-30)
5.5 (4-7) 5.5 (5-6.5) 3.5 (2-5)
References
(12–15) (12–14,16) (12–15,17) (12–15) (12–15,18,19) (12–14)
Quantifying reporting timeliness to improve outbreak control 91
to be assessed and compared to various diseases, timeliness needs to be evalu- ated in terms of the number of infections which could not be prevented because of the delay, rather than in terms of the actual time cases taken to be reported.
Table 1. Parameters for reporting delay models, by disease. All distributions are fitted to log-normal distributions with medians and standard deviations as indicated. Reporting delay distribution of pertussis is an exception, which is fitted to a gamma distribution.
¥ The reproduction numbers are those used for outbreak control calculations, and the ranges in brackets are those found in literature.
Ф For shigellosis, an average transmission period (serial interval distribution) of 1 week (median 5 d) was assumed, although in practice shedding continues after that.
When a case is reported, regional PHAs implement mostly case-based interven- tions. These interventions are intended to prevent transmission from the repor- ted case and from secondary cases that may have been acquired from the index case. Secondary cases are identified by contact tracing. For this reason, for each disease we first calculated the proportion of expected infections produced by an index case (PIR1) until the moment the index case in question is reported to the local PHA. We then calculated the proportion of expected infections produ- ced by each secondary case produced by a reported index case (PIR2), until the moment the index case in question is reported to the local PHA. Throughout this study we refer to an index case as any case that is reported because of a positive diagnosis and a case that has not yet been traced as a secondary case when reported ( i.e., all primary cases that may result in clusters). For every calculation we considered the hypothetical intervention in which contact cases and stopping of transmission occur instantly when the index case is reported.
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