Page 42 - Timeliness of Infectious Disease Notification & Response Systems - Corien Swaan

40 Chapter 2
bly occur before the onset of infectiousness in a possible secondary case. As a secondary case can be infected before symptom onset in the index patient, this time interval must be subtracted from the LP. We therefore defined a corrected time interval (Ic) as the interval from symptom onset in the index case to the start of infectiousness in one or more secondary cases. As shown in Figure 2: Ic (interval corrected) = LP (latent period) – x (period of infectiousness in index patient preceding symptom onset) For HAV infections, x is about 7 days; for measles, x is 1-2 days. Thus the Ic for HAV infection is 14 days, given the LP of 21 days. The Ic for measles is 7 days, given the LP of 8-9 days.
Of the six diseases under study, shigellosis and HAV infection were used in the calculation of distribution means of Po and Pd per year, in order to identify possible trends or changes over the years.
The percentage of notifications occurring more than three days after labora- tory diagnosis was calculated per disease. We devised a hypothetical scenario with an interval Pd of zero to demonstrate the improvement made possible by immedi- ate reporting (on the day of laboratory diagnosis), using fax, telephone, or e-mail.
All MHS (n=31) in the Netherlands participated and were sent a question- naire regarding timeliness and methods of reporting hepatitis B virus (HBV) in- fection in the year 2008. This disease was chosen because, unlike many of the other six, it is reported frequently enough over the years, that data could be expected from all MHS in all parts of the country.
The questionnaire asked whether physician-laboratory-MHS agreements were in place to allow direct reporting of cases of HBV infections by laborato- ries. It inquired about methods of reporting (post/fax/phone/e-mail) and the numbers of “report cards” received by post each week. The MHS respondents whose questionnaires mentioned experience with direct laboratory reporting by e-mail were interviewed by telephone about the number of these reports, the speed of reporting and the security of their inhouse electronic mail system.
All analyses were performed in SPSS version 17. Statistical analysis was performed using Independent Samples T-test and One-Way analysis of variance (One-Way ANOVA, post hoc Multiple Comparisons).