Table 1.

Summary of cross-sectional studies

Country	Type of test	Source of assay	Total cases	Antigenic strain	Positivity cutoff titer	Antibody target	Positivity criteria	Cutoff justification	Reference
American Samoa	IFA	NA	197	NA	1:50	IgG	Single titer	NA	44
Brazil	IFA	NA	437	NA	> 1:64	IgM	Both	NA	45
					≥ 4-fold increase	IgM
					1:64	IgG	Single titer
Croatia	IFA	Virus Reference Laboratory, London, UK	425	NA	≥ 1:16	IgG	Single titer	NA	46
Djibouti	IFA	NA	12,300	NA	≥ 1:80	NA	Both	36	47
					≥ 4-fold increase	NA
Greece	IFA	Biomerieux, Marcy l'Etoile, Lyon, France	1,584	NA	≥ 1:64	IgG	Single titer	NA	48
Indonesia	IFA	NA	142	NA	≥ 1:80	NA	Single titer	32,35	49
Lao PDR	IFA	NA	427	NA	> 1:64	IgM	Both	6,31	50
					≥ 4-fold increase	IgM and IgG
					> 1:128	IgG
Madagascar	IFA	NA	31	NA	1:4000	IgG	Single titer	NA	51
Malaysia	IFA	NA	1596	Wilmington	≥ 1:50	Whole	Single titer	52	53
Morocco	IFA	Biomerieux, Marcy l’Etoile, Lyon, France	300	Moroccan strain	≥ 1:32	NA	Single titer	20,21	15
Nepal	IFA	NA	103	Wilmington	≥ 1:400	IgM	Both	17	54
					≥ 4-fold increase	IgM
New Zealand	IFA	Australian Rickettsial Reference Laboratory, Victoria, Australia	989	NA	≥ 1:128	IgG	Single titer	Manufacturer’s specifications	39
Singapore	IIP	U.S. Army Medical Research Unit, Malaysia	35	NA	≥ 1:1600	IgG	Both	Manufacturer’s specifications	38
					≥ 1:400	IgG
					≥ 4-fold increase	IgG
Spain	IFA	NA	341	NA	1:40 – 1:160	NA	Range	NA	55
	IFA	Biomerieux, Marcy l'Etoile, Lyon, France	662	NA	≥ 1:80	IgG	Single titer	Manufacturer’s specifications	37
	IFA	Focus technologies, Cypress, CA	734	NA	≥ 1:64	IgM	Both	NA	56
					≥ 4-fold increase	IgM
					≥ 1:64	NA
	IFA	NA	104	NA	≥ 1:512	IgG	Both	NA	57
					≥ 4-fold increase	IgG
	IFA	NA	640	Wilmington	≥ 1:128	IgG	Single titer	NA	14
					≥ 1:40	IgM, IgG, IgA	Single titer
	IFA	MRL Diagnostics, Cypress, CA	217	NA	≥ 1:40	IgG	Single titer	NA	58
	IFA	NA	400	NA	1:40	NA	Single titer	NA	59
	IFA	Focus technologies, Cypress, CA	504	ref no. IF0100	≥ 1:64	NA	Single titer	NA	60
	IFA	NA	383	Wilmington	≥ 1:80	IgG	Single titer	NA	61
	IFA	Biomerieux, Marcy l'Etoile, Lyon, France	356,266	NA	≥ 1:40	NA	Single titer	NA	62
Taiwan	IFA	Taiwan CDC, Taipei, Taiwan	226	NA	≥ 1:80	IgM	Single titer	NA	63
					≥ 4-fold increase	IgG	Only 4-fold
	IFA	Taiwan CDC, Taipei, Taiwan	1420	NA	≥ 4-fold increase	NA	Only 4-fold	NA	64
Tanzania	IFA	NA	870	Wilmington	≥ 1:64	IgM	Single titer	NA	65
					≥ 4-fold increase	IgG	Only 4-fold
	IFA	NA	150	ATCC AZ332	> 1:50	Whole	Single titer	21	66
Tunisia	IFA	NA	500	NA	≥ 1:32	Whole	Single titer	20	67
	IFA	NA	47	NA	≥ 1:32	IgM	Single titer	NA	68
	IFA	NA	1024	NA	> 1:128	IgG	Single titer	NA	69
					≥ 1:32	IgM	Single titer
United States	IFA	NA	204	NA	≥ 1:64	IgG	Single titer	NA	70
	IFA	Focus technologies, Cypress, CA	152	NA	≥ 1:64	IgG	Single titer	NA	71
Vietnam	IFA	In-house	193	Wilmington	1:400	IgG	Both	54	72
					≥ 4-fold increase	IgG
Zambia	IFA	NA	377	Wilmington	≥ 1:32	IgM	Single titer	NA	73
					≥ 1:64	Whole	Single titer

IFA = immunofluorescence assay; IIP = immunoperoxidase assay.