Transmission Classification Model To Determine Place and Time of Infection of Tuberculosis Cases in an Urban Area

G. de Vries; H. W. M. Baars; M. M. G. G. Šebek; N. A. H. van Hest; J. H. Richardus

doi:10.1128/JCM.00793-08

DOI: 10.1128/JCM.00793-08

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FIG. 1.
Classification of time of infection for clustered cases from the Rotterdam area that were probably or confirmed infected in The Netherlands, 1995 to 2006 (n = 994). PTB, pulmonary tuberculosis; EPI link, epidemiological link.

TABLE 1.

Selected demographic and disease-related factors of 2,636 TB cases in the Rotterdam region, 1995 to 2006

Patient characteristic	No. or % of TB cases with indicated type of fingerprint
	Unique		Clustering		Unknown
	No.	%	No.	%	No.	%
Total no.	919		1,108		609
Male	485	52.8	738	66.6	322	52.9
Age (yr)
0-14	15	1.6	32	2.9	109	17.9
15-29	258	28.1	386	34.8	145	23.8
30-44	276	30.0	400	36.1	157	25.8
45-64	164	17.8	229	20.7	121	19.9
≥65	206	22.4	61	5.5	77	12.6
Born in The Netherlands	219	23.8	338	30.5	273	44.8
Previous history of TB	68	7.4	58	5.2	35	5.7
HIV infection	51	5.5	50	4.5	13	2.1
Illicit drug user or homeless person	25	2.7	157	14.2	19	3.1
Pulmonary TB	576	62.7	811	73.2	271	44.5
Active case found by contact investigation	11	1.2	107	9.7	121	19.9
Active case found by screening	99	10.8	108	9.7	57	9.4

TABLE 2.

Classification of place and time period of transmission of TB cases in the Rotterdam region, 1995 to 2006

Criterion^a	Place of infection					Time of infection for patients infected in The Netherlands^e
	Infected in a foreign country		Indeterminate^b	Infected in The Netherlands		≤2 yrs	>2 yrs	Unknown
	Confirmed	Probably	Indeterminate^b	Probably	Confirmed	≤2 yrs	>2 yrs	Unknown
Cases with a unique fingerprint (n = 919)
Cases in immigrants (n = 700)
Arrived in The Netherlands after 1/1/1993	376
In residence before 1/1/1993 and had documented contact with PTB case in The Netherlands				18	1	1^c	18
In residence before 1/1/1993 and had documented history of frequent travel to countries where TB is endemic		79
In residence before 1/1/1993 and lived more yrs in foreign country than in The Netherlands in the pregenotyping period		170
In residence before 1/1/1993 without identified risks			56
Cases in nonimmigrants (n = 219)
Documented contact with PTB case in The Netherlands					39	1^c	38
Documented history of frequent travel to countries where TB is endemic		32
No documented risks				148			148
Cases with a clustering fingerprint (n = 1,108)
No preceding PTB in the cluster^d (n = 62)	29	21		12		2 ^c	10
Diagnosis within 3 mo of arrival	32
Not in residence in The Netherlands with a clustered TB case	32
Cases with a confirmed epidemiological link					258	195	63
Cases with a possible epidemiological link					190	185	5
Cases without an established epidemiological link				534		401	133
Cases without a DNA fingerprint (n = 609)
Documented contact with PTB case in The Netherlands					192	154	38
Documented contact with PTB case in a foreign country	13
Chest X-ray abnormalities or positive TST at entrance screening	43
Cases in immigrants who lived more yrs in a foreign country than in The Netherlands		151
Cases in immigrants without other documented risks			70
Cases in nonimmigrants with documented history of frequent travel to countries where TB is endemic		14
Cases of recurrent TB in nonimmigrants				13			13
Cases in nonimmigrants without documented risks				113				113
Total (n = 2,636)	525	467	126	838	680	939	466	113
%	19.9	17.7	4.8	31.8	25.8	35.6	17.7	4.3

↵ a Dates are given as month/day/year. PTB, pulmonary tuberculosis; TST, tuberculin skin test.
↵ b Twenty-two of 56 and 21 of 70 cases had unknown dates of arrival in The Netherlands.
↵ c Patients were infected by a visiting person later diagnosed with infectious TB shortly after leaving The Netherlands.
↵ d These clustered cases without a preceding PTB were classified according to the trees for unique fingerprints.
↵ e The classification of time of infection for 994 clustered cases infected in The Netherlands, presented in boldface in this table, is explained in Fig. 1.

TABLE 3.

Contribution to cluster size in The Netherlands of clustered cases from the Rotterdam region that were not the first in the cluster and their classification of transmission, 1995 to 2006

Patient's sequential no. in national clusters	Total no. of regional cases	No. (%) of patients that were:
Patient's sequential no. in national clusters	Total no. of regional cases	Infected in a foreign country	Recently infected in The Netherlands	Remotely infected in The Netherlands
2	184	55 (29.9)	70 (38.0)	59 (32.1)
3	98	18 (18.4)	49 (50.0)	31 (31.6)
4-5	121	10 (8.3)	76 (62.8)	35 (28.9)
6-10	195	18 (9.2)	144 (73.8)	33 (16.9)
11-20	168	8 (4.8)	130 (77.4)	30 (17.9)
21-50	197	4 (2.0)	178 (90.4)	15 (7.6)
≥51	145	1 (0.7)	135 (93.8)	8 (5.5)
Total	1,108	114 (10.3)	783 (70.7)	211 (19.0)

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Supplemental file 1 - Transmission classification trees for recurrent TB, for immigrant cases, for nonimmigrant cases, for cases with a clustering fingerprint, and for cases with an unknown fingerprint).
MS Word document, 284K.