Table 1.

Characteristics of included comparative studies

	n	Country	Setting	Disease caused by virus	Case definition (WHO)	Adjusted estimates	Risk of bias*
Alraddadi et al (2016)34	283	Saudi Arabia	Health care	MERS	Confirmed	Yes	********
Arwady et al (2016)35	79	Saudi Arabia	Non-health care (household and family contacts)	MERS	Confirmed	No	******
Bai et al (2020)36	118	China	Health care	COVID-19	Confirmed	No	*****
Burke et al (2020)37	338	USA	Health care and non-health care (including household and community)	COVID-19	Confirmed	No	****
Caputo et al (2006)38	33	Canada	Health care	SARS	Confirmed	No	*****
Chen et al (2009)39	758	China	Health care	SARS	Confirmed	Yes	*******
Cheng et al (2020)40	226	China	Non-health care (household and family contacts)	COVID-19	Confirmed	No	******
Ha et al (2004)42	117	Vietnam	Health care	SARS	Confirmed	No	**
Hall et al (2014)43	48	Saudi Arabia	Health care	MERS	Confirmed	No	***
Heinzerling et al (2020)44	37	USA	Health care	COVID-19	Confirmed	No	****
Ho et al (2004)45	372	Taiwan	Health care	SARS	Confirmed	No	********
Ki et al (2019)47	446	South Korea	Health care	MERS	Confirmed	No	******
Kim et al (2016)48	9	South Korea	Health care	MERS	Confirmed	No	*****
Kim et al (2016)49	1169	South Korea	Health care	MERS	Confirmed	No	******
Lau et al (2004)50	2270	China	Non-health care (households)	SARS	Probable	Yes	******
Liu et al (2009)51	477	China	Health care	SARS	Confirmed	Yes	*****
Liu et al (2020)52	20	China	Non-health care (close contacts)	COVID-19	Confirmed	No	*******
Loeb et al (2004)53	43	Canada	Health care	SARS	Confirmed	No	**
Ma et al (2004)54	426	China	Health care	SARS	Confirmed	Yes	*********
Nishiura et al (2005)55	115	Vietnam	Health care	SARS	Confirmed	Yes	********
Nishiyama et al (2008)56	146	Vietnam	Health care	SARS	Confirmed	Yes	******
Olsen et al (2003)57	304	China	Non-health care (airplane)	SARS	Confirmed	No	******
Park et al (2004)58	110	USA	Health care	SARS	Confirmed	No	**********
Park et al (2016)59	80	South Korea	Health care	MERS	Confirmed and probable	No	***
Peck et al (2004)60	26	USA	Health care	SARS	Confirmed	No	*********
Pei et al (2006)61	443	China	Health care	SARS	Confirmed	No	********
Rea et al (2007)62	8662	Canada	Non-health care (community contacts)	SARS	Probable	No	****
Reuss et al (2014)63	81	Germany	Health care	MERS	Confirmed	No	*****
Reynolds et al (2006)64	153	Vietnam	Health care	SARS	Confirmed	No	***
Ryu et al (2019)65	34	South Korea	Health care	MERS	Confirmed	No	******
Scales et al (2003)66	69	Canada	Health care	SARS	Probable	No	**
Seto et al (2003)67	254	China	Health care	SARS	Confirmed	Yes	********
Teleman et al (2004)68	86	Singapore	Health care	SARS	Confirmed	Yes	********
Tuan et al (2007)69	212	Vietnam	Non-health care (household and community contacts)	SARS	Confirmed	Yes	******
Van Kerkhove et al (2019)46	828	Saudi Arabia	Non-health care (dormitory)	MERS	Confirmed	Yes	********
Wang et al (2020)41	493	China	Health care	COVID-19	Confirmed	Yes	****
Wang et al (2020)70	5442	China	Health care	COVID-19	Confirmed	No	*****
Wiboonchutikul et al (2016)71	38	Thailand	Health care	MERS	Confirmed	No	*****
Wilder-Smith et al (2005)72	80	Singapore	Health care	SARS	Confirmed	No	********
Wong et al (2004)73	66	China	Health care	SARS	Confirmed	No	*****
Wu et al (2004)74	375	China	Non-health care (community)	SARS	Confirmed	Yes	********
Yin et al (2004)75	257	China	Health care	SARS	Confirmed	Yes	******
Yu et al (2005)76	74	China	Health care	SARS	Confirmed	No	*******
Yu et al (2007)77	124 wards	China	Health care	SARS	Confirmed	Yes	*******

Across studies, mean age was 30–60 years. SARS=severe acute respiratory syndrome. MERS=Middle East respiratory syndrome.

^*The Newcastle-Ottawa Scale was used for the risk of bias assessment, with more stars equalling lower risk.