Table. Number of emm1 invasive group A Streptococcus (iGAS) infections, 1 May 2022–14 August 2023 (n = 518), and number of M1_UK lineage among sequenced emm1 S. pyogenes causing iGAS infections, May 2022–May 2023 (n = 130) by age, Belgium.

Case characteristics						emm1 iGAS infectionsa				Sequenced emm1 iGASb		M1 UK in iGAS infectionsd		M1 global in iGAS infectionsd		M1 UK causing BSIse
Age range (years)	Total	Sexb,c				May−Dec 2022		Jan−Aug 2023
		Males		Females
		n	%	n	%	n	%	n	%	n	%	n	%	n	%	n	%
0–12	160	86	54	74	46	64	36	96	28	40	25	27	68	12	30	19	70
13–17	4	2	50	2	50	1	1	3	1	1	25	1	100	0	0	1	100
18–40	85	36	42	49	58	26	15	59	17	34	40	26	76	8	24	19	73
41–65	129	76	59	53	41	46	26	83	24	31	24	27	87	4	13	22	81
> 65	135	65	48	69	51	38	21	97	28	22	16	20	91	2	9	16	80
Unknown	5	3	60	2	40	2	1	3	1	2	40	1	50	1	50	1	100
Total	518	268	52	249	48	177	100	341	100	130	25	102	78	27	21	78	76

BSIs: bloodstream infections; iGAS: invasive group A Streptococcus.

^a For emm1 iGAS infections: % based on total isolates in that period.

^b For sex and sequenced isolates: % based on total number of isolates per age group.

^c Sex is unknown for one case in the > 65 age group.

^d For M1 isolates: % based on sequenced isolates. The dataset for lineage assignment is limited to the emm1 iGAS isolated during May 2022–May 2023 that underwent whole genome sequencing (n = 130).

^e For M1_UK causing BSI: % based on M1_UK causing iGAS.