Table 1. Characteristics of included studies, sorted by year of study.

First author, Journal [Reference]	Region, Study period	Study design, characteristics	No. untreated patients	Age, Years (mean)	Sex male (%)	Duration of fever, days	Diagnostic test used	Complications	Patients hospitalised (%)	Untreated deaths % (n)
Crofton, JRAMC [9]	Middle East, countries not specified 1942–1943	Retrospective case series Middle East Forces	28 (28/28)	-	-	-	Rickettsial agglutination test with differentiation from R. prowazekii for all patients plus Weil-Felix.	Five “severe” cases, of which one died (post-mortem—lung with haemorrhagic bronchopneumonia and abscess formation, brain with microscopic haemorrhages and scanty cellular nodes)	all	3.6% (1/28)
Calero, AJTMH [10]	Panama City, Panama 1947	Prospective case series Report of an outbreak	13 (13/13)	16–43	11/13 (85%)	12–17 (15)	Ten cases confirmed by complement or rickettsial agglutination test with differentiation from R. prowazekii plus Weil-Felix, three cases by Weil-Felix only	Seven patients hospitalised Pronounced “stuporous condition” in 30.7%	7/13 (54%)	0% (0/13)
Diaz-Rivera, Am J Med Sci [11]	San Juan, Puerto Rico 1947–1948?	Prospective case series Drug trial, 33 treated	27 (27/60)	15–60 (30.6)	18/27 (67%)	12–22 (15)	Complement fixation test with conversion from negative to positive plus Weil-Felix with increasing titers up to ≥ 1:160	-	all	0% (0/27)
Shaked, Infection [12]	Israel 1976–1985	Retrospective case series Chart review	11 (11/45)	-	-	12–19	Positive complement fixation test or immunofluorescent antibody test for murine typhus with differentiation from spotted fever (unspecified antigens/titer)	One case of encephalitis Two cases of pneumonia and one scrotal ulcer in treated patients	all	0% (0/11)
		34 treated		-	34/45a (76%)
Dumler, JAMA [13]	Southern Texas, US 1980–1987	Retrospective case series Chart review	8 (8/80)	-	-	-	Indirect fluorescent antibody test (IFA) with 4-fold rise in typhus group antibody titer, single high titer ≥ 1:128 and lower titer to spotted fever group (R. rickettsii) antigen than to typhus group antigen No differentiation from R. prowazekii, previous studies revealed no cases of R. prowazekii infection	No complications in the untreated Neuropsychiatric complications (confusion, stupor, coma, hallucinations) in six, seizure in three, ataxia in one, renal insufficiency in five, jaundice in two, respiratory failure in three and hematemesis in one of the treated patients Seven patients admitted to ICU, three (3.8%) died. Two deaths due to shock, renal and multisystem failure	77/80 (96%)	0% (0/8)
		72 treated		- (46.3)a	- (40%)a	-
Bernabeu-Wittel, Arch Intern Med [14]	Sevilla, Spain 1979–1995	Prospective case series 1983–1995 62 cases Retrospective case series 1979–1982 42 cases Hospital in Spain	60 (60/104)	-	-	- (12.7)	Immunofluorescence antibody assay R. typhi IgG ≥ 1:512 in 76 patients, 4-fold rise in titer in 28 patients, differentiation from Rickettsia conorii	Organ complications in four untreated patients (6.7%) Nine of all 104 patients (8.6%) with organ complications, including pneumonitis in six, cerebellitis in one and multiorgan failure in two patients Complications classified as severe in four of 104 patients (3.8%)	all	0% (0/60)
		44 treated		12–81a (37.9)	57/104a (55%)	8–27a (12.5)
Hernández-Cabrera, Emerg Infect Dis [15]	Gran Canaria, Canary Islands, Spain 2000–2002	Not specified in- and outpatients (>14 years) at University Hospital Las Palmas	8 (8/22)	-	-	-	Direct immunofluorescence antibody test R. typhi IgM ≥ 1:40 or 4-fold rise in IgG titer and differentiation from Rickettsia conorii	No complications in the untreated One renopulmonary syndrome, one encephalitis and one meningitis with renal failure in the treated	Not specified	0% (0/8)
		14 treated		14–76a (28)	21/22a (95%)	7–20a (10)
Shalev, Scand J Infect Dis [16]	Rahat, Israel 2003–2005	Prospective case series Bedouin children	47 (47/76)	-	-	-	Micro immunofluorescence R. typhi titer IgM or IgG ≥ 1:100 in acute and/or convalescent sample and stronger reaction to R. typhi antigen than to spotted fever group (R. conorii) antigen	No complications	1/76 (1.3%)	0% (0/47)
		29 treated		- (7.3)a	39/76a (51%)	-
Gray, N Z Med J [17]	Waikato region, New Zealand 2006	Retrospective case series	5 (5/12)	-	-	-	IFA with 4-fold R. typhi antibody titer rise in six patients and single high IgM ≥ 1:512 or IgG ≥ 1:1024 in six patients	- Nine patients hospitalised	9/12 (75%)	0% (0/5)
		Seven patients treated		19–69a (46)	6/12a (50%)	-
Adjemian, Emerg Infect Dis [18]	Austin, Texas, US 2008	Retrospective case series Outbreak investigation	16 (16/33)	-	-	-	IFA with 4-fold antibody titer rise to R. typhi in all and detection of DNA in clinical specimen by PCR in one patient	- 23 of all 33 patients hospitalised and 9 of them admitted to the ICU (pneumonia, coagulopathy, renal failure)	23/33 (70%)	0% (0/16)
		17 treated		7–64a (39)	- (56%)a	-
Znazen, Med Mal Infect [19]	Tunisia 2006–2008	Retrospective case series	8 (8/43)	-	-	-	Micro immunofluorescence assay with IgM titer ≥ 1:32 to R. typhi in 32 and seroconversion or significant titer rise in 11 patients, sera showing cross-reactions between R. typhi and R. conorii or R. felis were excluded	- 36 patients hospitalised	36/43 (84%)	0% (0/8)
		35 patients treated		8–83a (41)	- (51%)a	-
Afzal, Emerg Infect Dis [20]	Hidalgo County, Texas, US 2013–2016	Retrospective case series Review of records from two hospitals	8 (8/90)	-	-	-	IFA with IgM or IgG titer ≥ 1:128 to typhus group rickettsiae in 87, 4-fold IgG titer rise in three patients	- Complications in 25 patients, including bronchiolitis in two, pneumonia in eight, pancreatitis in three, cholecystitis in one, myositis in one, rhabdomyolysis in two, meningitis in two, sepsis with acute kidney injury in one, septic shock in four patients and septic shock plus pneumonia in one patient. 13 patients required ICU care	all	0% (0/8)
		82 patients treated		-	45/90a (50%)	-

“-”refers to missing information.

^a entire study population, including treated patients.