Page 92 - Timeliness of Infectious Disease Notification & Response Systems - Corien Swaan

90 Chapter 4
Figure 1. Timeline fo chain of disease reporting, The Netherlands. Lab, laboratory; PHA, public health authority
Methods
For evaluation of reporting timeliness, we selected 6 notifiable diseases that are transmitted person to person, and for which sufficient data on total reporting delays (DOR) are available in the notification system in the Netherlands (OSIRIS): hepatitis A, hepatitis B, measles, mumps, pertussis and shigellosis. For 5 of tho- se diseases we obtained data for day of symptom onset and day of reporting to the PHA for cases reported between July 2003 through December 2011. The other disease, mumps, was a notifiable disease in the Netherlands until 1999, when it was dropped from the notification list because of a decreased number of cases. However, with a resurgence in mumps in 2008, it was reintroduced as a notifiable disease in OSIRIS in 2009. Therefore, no mumps data were available during 1999-2008. We included mumps into our analysis because of its high incidence even though control measures are limited, similar to the situation with pertussis. To model the reporting delay for each disease, we fitted analyti- cal log-normal distributions to the OSIRIS data. We also used log-normal distri- butions that fit serial interval and time-to-symptom onset ranges found in the literature (Table 1).
The course of infection of each disease has its own characteristic time scale (latent, infectious and symptomatic periods). This implies that a 1-week delay may have a significant effect on control of a slowly progressing disease such as hepatitis A but not on a rapidly progressing diseases such as shigellosis. More- over, reporting itself also has its own time scale because of various causes be- hind each link in the reporting chain. Therefore, for timeliness of case reporting