Applying cusum-based methods for the detection of outbreaks of Ross River virus disease in Western Australia

Table 1 Algorithm summary performance statistics for false alarm rates approximating 0.005^†

Algorithm	false alarm rate	median (mean) sensitivity	Day 1 sensitivity	Day 2 sensitivity	Days 1–7 sensitivity	CARL	median (mean) timeliness^‡	median (mean) adjusted timeliness^‡
EARS C1	0.0049	1 (0.53)	0.13	0	0.13	1.0	18.5 (54.6)	34.0 (78.8)
EARS C2	0.0042	1 (0.53)	0.33	0	0.33	1.0	0.0 (24.1)	32.0 (71.1)
EARS C3	0.0049	1 (0.60)	0.40	0	0.40	1.0	0.0 (17.9)	32.0 (68.1)
NBC 7-day	0.0049	1 (0.87)	0.2	0.07	0.40	2.0	12.0 (16.3)	14.0 (18.5)
NBC 14-day	0.0049	1 (0.93)	0.2	0.07	0.33	1.6	9.5 (13.9)	11.0 (15.2)
NBC 28-day	0.0049	1 (1.00)	0.27	0.07	0.60	2.9	5.0 (8.5)	5.0 (8.5)
NBC 56-day	0.0042	1 (0.93)	0.13	0	0.27	3.0	14.5 (19.1)	14.0 (18.8)
p-value^¥	-	0.0002	-	-	-	-	0.71	0.008

^†Test threshold that produced a false alarm rate ≤ 0.005
^‡Detection on the first outbreak day is equivalent to a timeliness of 0 days
^¥Friedman rank sum test
CARL: Conditional Average Run Length – conditional on the detection of the outbreak during the first 7 days
EARS: Early Aberration Reporting System
NBC: Negative binomial cusum with an out of control state defined as 2 standard deviations greater than the mean

ISSN: 1472-6947