Using statistical methods and genotyping to detect tuberculosis outbreaks

Table 3 Tuberculosis cases occurring after outbreak detection by retrospectively applied statistical methods, 2008–2009

Outbreak	Outbreak cases^a, n	Cases occurring after detection^b, n (%)	Outbreak duration, months^c	County size, sq km^d	County population^d
A	16	16^e (100)	9	290	865,000
B	13	10 (76.9)	14	200	926,000
C	5	3 (60.0)	3	150	905,000
D	7	3 (42.9)	8	280	532,000
E	3	0 (0)	43	280	21,000
F	5	0 (0)	3	210	178,000
G	8	0 (0)	26	3050	1,954,000
H	16	14 (87.5)	15	150	742,000
I	4	0 (0)	27	NA^f	NA^f
Total	77	46 (59.7)

^a Culture-positive and culture-negative cases reported in 2005–2009, and confirmed to be part of the outbreak at the end of the Centers for Disease Control and Prevention investigation.
^b Confirmed outbreak cases that occurred after the earliest date of detection among the three retrospectively applied statistical methods, and before the local public health authorities first noticed the outbreak.
^c Computed using culture-positive and culture-negative cases reported in 2005–2009, and confirmed to be part of the outbreak at the end of the Centers for Disease Control and Prevention investigation.
^d From 2010 U.S. Census, county size rounded to the nearest 10 sq km, county population rounded to nearest thousand persons.
^e Outbreak A included earlier cases that were not contained in the outbreak cases list developed during the investigation.
^f Outbreak spans multiple counties.

ISSN: 1476-072X