The role of super-spreading events in Mycobacterium tuberculosis transmission: evidence from contact tracing

BMC Infectious Diseases

Table 1 Associations between number of secondary infections and patient characteristics among pulmonary TB index patients in Victoria, 2005–2015. Negative binomial regression model

Variable		Number of index patients	Crude RR (95%CI)	Adjusted RR (95%CI)
Age category (years)	0–14	140	0.43 (0.30–0.62)*	0.84 (0.56–1.26)
	15–24	486	1.60 (1.32–1.95)*	0.94 (0.80–1.11)
	25–44	890	Referent
	45–64	378	0.77 (0.61–0.96)*	1.02 (0.85–1.22)
	65 and above	417	0.93 (0.75–1.15)	0.91 (0.77–1.09)
Sex	Female	954	Referent
Sex	Male	1357	0.95 (0.81–1.10)	0.93 (0.82–1.05)
Site of disease	Pulmonary	1757	Referent
Site of disease	Pulmonary plus additional sites	555	0.51 (0.43–0.62)*	0.58 (0.50–0.68)*
Patient detection pathway	Clinical Presentation	1839	Referent
	Contact tracing	131	0.132 (0.08–0.21)*	0.29 (0.18–0.46)*
	Screening	24	0.49 (0.23–1.11)	0.64 (0.33–1.22)
	Health undertaking	317	0.37 (0.29–0.46)*	0.54 (0.44–0.67)*
CXR	Normal	31	Referent
	Abnormal	879	1.79 (0.84–3.60)	1.18 (0.66–2.12)
	Unknown	1401	1.95 (0.91–3.91)	1.27 (0.71–2.26)
Diagnosis	Culture	1967	Referent
	PCR/NAT/Ht/Cs	130	0.15 (0.09–0.23)*	0.30 (0.19–0.45)*
	Radiological	214	0.21 (0.15–0.29)*	0.45 (0.33–0.62)*
New or relapse	New case	2177	Referent
	Relapse following full treatment	83	1.23 (0.84–1.86)	1.07 (0.78–1.47)
	Relapse following partial treatment	30	0.53 (0.26–1.14)	0.70 (0.38–1.25)
	Unknown	21	1.38(0.67–3.24)	1.02(0.56–1.91)
Number of contacts identified		18019^a	1.06(1.05–1.06)*	1.04(1.04–1.05)*

RR rate ratio, CI confidence interval, CXR Chest X-Ray, PCR/NAT/Ht/Cs Polymerase chain reaction/nucleic acid test/histology/clinical signs, Health undertaking is post migration follow-up program
^a=total number of contacts, * = statistically significant at P value < 0.05

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