Table 1. Overview of study, method, and assessment characteristics described in articles included in a systematic review on approaches to determine seasonality of respiratory syncytial virus epidemics, 2016−2021 (n = 32 articles).

Elements considered			Number of analyses	Total number of analyses in the studies	%	Citations of the studies
Study features	Geographical scope	Regional	5	32	16%	[1,25,27,40,41]
		National	16	32	50%	[12,13,20,22,23,26,42-51]
		Subnational	11	32	34%	[52-62]
	Provenance of the study (WHO region/global)	African	1	32	3%	[59]
		Americas	15	32	47%	[20,22,23,26,42,44,46-50,54,56,60,61]
		European	10	32	31%	[12,13,25,41,43,45,53,55,57,62]
		Western Pacific	2	32	6%	[51,52]
		South-East Asian	1	32	3%	[58]
		Global	3	32	9%	[1,27,40]
	Purpose of data collection	Surveillance	20	32	63%	[12,13,20,22,23,25,26,40,41,43,44,46-50,55,56,59,62]
		Other	12	32	38%	[1,27,42,45,51-54,57,58,60,61]
Attributes of the analysisa	Timing of analysis	Retrospective	30	32	94%	[1,12,13,20,22,23,25-27,40-42,44,45,47-62]
		Real-time	1	32	3%	[43]
		Prospective	1	32	3%	[46]
	Transformation method	Yes	10	32	31%	[12,20,22,40,42,43,46,52,56,59]
		No	22	32	69%	[1,13,23,25-27,41,44,45,47-51,53-55,57,58,60-62]
	Methodsb	Percentage positive threshold: 10%	18	49	37%	[13,22,23,27,40,44,46-48,52,54,55,57,62]
		Percentage positive threshold: various others	7	49	14%	[13,22,23,49]
		Number of detections threshold: various	5	49	10%	[12,20,22,42]
		Percentage of detections threshold: 1.2%	3	49	6%	[12,13,25]
		Percentage of detections: various others	4	49	8%	[41,50,53,58]
		Mean detections threshold: 60% threshold	2	49	4%	[13,60]
		Mean detections threshold: various others	2	49	4%	[45,61]
		Mean % positive threshold	3	49	6%	[26,51,59]
		Average annual percentage	1	49	2%	[1]
		Change point analysis	1	49	2%	[56]
		Moving epidemic method (MEM)	3	49	6%	[12,13,43]
Assessment characteristics	Year-round data collection	Yes	20	32	63%	[12,13,20,23,26,40,43,45,47,49,51-53,56-62]
		No	3	32	9%	[44,48,55]
		Unknown	9	32	28%	[1,22,25,27,41,42,46,50,54]
	Age group sampled	All ages	13	32	41%	[12,13,22,23,26,40,44,46,48,55,57-59]
		Children (< 18 years old)	10	32	31%	[43,45,47,51-54,60-62]
		Unknown	9	32	28%	[1,20,25,27,41,42,49,50,56]
	Setting	Inpatient	9	32	28%	[42,45,47,50-54,57]
		Outpatient	3	32	9%	[43,55,58]
		Mix	10	32	31%	[12,13,20,26,40,41,48,56,59,62]
		Unknown	10	32	31%	[1,22,23,25,27,44,46,49,60,61]
	Case definition for test inclusionc	ALRI	2	32	6%	[47,54]
		ARI	1	32	3%	[57]
		ILI	2	32	6%	[55,58]
		SARI	0	32	0%	No study
		ICD codes for RSV	3	32	9%	[42,45,51]
		Other/mixd	10	32	31%	[12,25,26,40,43,50,52,53,59,62]
		Unknown	14	32	44%	[1,13,20,22,23,27,41,44,46,48,49,56,60,61]
	Diagnostics	Antigen	4	32	13%	[23,26,44,48]
		PCR	12	32	38%	[12,13,20,22,40,49,50,52,53,55,57,58]
		Other/mix	9	32	28%	[25,43,46,47,54,56,59,61,62]
		Unknown	7	32	22%	[1,27,41,42,45,51,60]

ALRI: acute lower respiratory infections; ARI: acute respiratory infection; ICD: International Classification of Diseases; ILI: influenza-like illness; RSV: respiratory syncytial virus; SARI: severe acute respiratory infection; WHO: World Health Organization.

^a Four studies [12,13,22,23] compared two or more methods with each other.

^b Number of overall methods (n = 49) is higher than the total of articles (n = 32) included as some studies compared several methods or implemented one method more than once with different assessment characteristics.

^c For respiratory infections (e.g. ARI and ILI), articles most commonly cited World Health Organization definitions, but not consistently.

^d This includes studies with a mix of any combination of either/and/or ARI.ILI, SARI, ALRI cases.