Table 1. Clinical manifestations of Lyme borreliosis, serology and exposure to ticks among tick bite cases with evidence of Borrelia infection within three months after a tick bite.

Case	Evidence of Borrelia infection		C6 ELISA index*		IgM immunoblot		IgG immunoblot		Borrelia in tick	Tick engorgement	hours of tick attachment
	Clinical	Seroconversion**	1st	2nd	1st	2nd	1st	2nd
1	yes (EM)	yes (IgG)	1.12	0.83	−	−	+/−	+	n.a.	n.a.	30
2	yes (EM)	yes (C6)	0.21	1.90	−	−	−	−	+ (untypeable Borrelia)	full	16
3	yes (EM)	no	0.49	0.52	+/−	+/−	−	−	+ (B. afzelii)	unengorged	60
4	yes (EM)	no	0.27	0.37	+/−	+/−	−	−	−	full	36
5	yes (EM)	no	0.47	0.43	−	−	−	−	n.a.	n.a.	8
6	yes (EM)	no	0.64	0.98	+/−	+/−	−	−	−	unengorged	30
7	yes (EM)	no	0.37	0.33	−	−	−	−	+ (untypeable Borrelia)	partial	15
8	no	yes (C6 & IgM & IgG)	0.40	3.79	−	+	−	+	n.a.	n.a.	26
9	no	yes (C6)	0.29	3.69	+/−	+/−	−	−	n.a.	n.a.	20
10	no	yes (C6 & IgM)	0.37	2.63	−	+	−	+/−	n.a.	n.a.	24
11	no	yes (C6 & IgM)	0.76	6.57	+/−	+	−	+/−	+ (untypeable Borrelia)	full	20
12	no	yes (C6)	0.42	7.01	−	+/−	−	+/−	−	partial	n.a.
13	no	yes (C6)	0.22	1.86	−	−	−	−	+ (B. afzelii)	partial	n.a.
14	no	yes (C6 & IgG)	0.26	5.84	−	−	−	+	+ (untypeable Borrelia)	partial	72
15 ‡	yes (neuroborreliosis)	no	4.12	6.49	+	+	+	+	−	Full	36

EM  =  erythema migrans; n.a.  =  no tick available for testing.

^*C6 ELISA test results were scored as negative (ELISA index score, <0.90), borderline (0.90 to 1.09), or positive (≥1.10).

^**Seroconversion of IgM and/or IgG in the immunoblot and/or in the C6 ELISA was considered as evidence of an early Borrelia infection. For seroconversion in the C6 ELISA, the ELISA index score was required to be <1.10 in the baseline serum, and ≥1.10 in the consecutive serum, with a minimum increase of 1.5 points.

^‡case #15 was excluded from risk analyses, as the development of Lyme borreliosis was almost certainly not attributable to the tick bite at baseline.