Table 1.

Summary of household studies of influenza A (H1N1-2009) included in the systematic review^a

	Location (City, Country)	Study Period	No. of Households	No. of Subjects	Recruitment Strategy^b	Multiple Index	Index case ascertainment	Primary Outcome	All contacts	Primary SIR, %	Secondary Outcome(s)	Secondary SIR(s), %	Follow-up duration of households	Serial interval (days)	Mean Household size	Serology Collected
Calatayud et al 2010¹⁸	London, UK	Apr 09 – May 09	n/a	47	Cohort	N	RT-PCR	RT-PCR	N	17%	n/a	n/a	n/a	n/a	n/a	N
Carcione et al 2011¹⁹	Western Australia	May 09 – Aug 09	595	2184	Case ascertained	N	RT-PCR	RT- PCR/FARI combined	N	20%	n/a	n/a	8	Mean: 3.2, Median: 3	3.8	N
Cauchemez et al 2009²⁰	USA	Apr 09 – May 09	216	816	Case ascertained	N	RT-PCR	ARI	N	13%	FARI	10%	7	Mean: 2.9	n/a	N
Chang et al 2011²¹	Taiwan	Aug 09 – Nov 09	87	223	Case ascertained	N	RT-PCR + serology	RT-PCR + serology	Y	27%	n/a	n/a	7	Mean: 2,.3	n/a	Y
Cowling et al 2010²²	Hong Kong	Jul 09 – Aug 09	105	309	Case ascertained	N	RT-PCR	RT-PCR	Y	7.8%	ARI, FARI	26%, 6.1%	7	Mean: 3.2	n/a	Y
Doyle et al 2011²³	USA	Jun 09	53	163	Case ascertained	Y	FARI	FARI	N	3.4%	n/a	n/a	n/a	Mean: 3	n/a	N
France et al 2010²⁴	New York, USA	Apr 09	322	1042	Case ascertained	N	RT- PCR/FARI	FARI	N	11%	n/a	n/a	n/a	Median: 3	4.1	N
Goldstein et al 2010²⁵	Milwaukee, USA	Apr 09 – Jun 09	135	546	Case ascertained	N	RT-PCR	FARI	N	13%	n/a	n/a	7	Mean: 3.32	n/a	N
Komiya et al 2010²⁷	Osaka, Japan	May 09	124	503	Case ascertained	N	RT-PCR	RT-PCR	N	3.7%	n/a	n/a	n/a	Median: 3	3.1	N
Leung et al 2011²⁸	Hong Kong	Jun 09	65	270	Case ascertained	N	RT-PCR	RT-PCR	N	5.9%	n/a	n/a	14	Mean: 2.8	n/a	N
Looker et al 2010²⁹	Victoria, Australia	May 09 – Aug 09	132	483	Case ascertained	N	RT-PCR	FARI	N	33%	n/a	n/a	n/a	n/a	3.9	N
Loustalot et al 2011³⁰	Texas, USA	May 09	668	640	Cohort	N	FARI	FARI	N	3.7%	n/a	n/a	10	n/a	n/a	N
Mohamed et al 2011³¹	Riyadh, Saudi Arabia	Sep 09 – Oct 09	69	432	Case ascertained	N	RT-PCR	FARI	N	17%	n/a	n/a	12	n/a	n/a	N
Morgan et al 2010³²	Texas, USA	Apr 09 – May 09	77	349	Case ascertained	N	RT-PCR/FARI	RT-PCR	N	4.2%	ARI, FARI	13%, 9.3%	9	Median: 4	n/a	N
Nishiura et al 2011³³	Japan	May 09 – Feb 10	1547	6156	Case ascertained	N	RT- PCR/FARI	FARI	N	11%	n/a	n/a	7	Mean: 3.1, Median: 3	n/a	N
Odaira et al 2009³⁴	Kobe, Japan	May 09 – Jun 09	97	400	Case ascertained	N	RT-PCR	RT-PCR	N	4.1%	ARI	4.8%	8	Mean: 2.9, Median: 3	n/a	N
Papenburg et al 2010³⁵	Quebec, Canada	May 09 – Jul 09	42	162	Case ascertained	Y	RT-PCR	RT-PCR + Serology	Y	45%	RT- PCR, ARI, FARI	38%, 51%, 29%	11	Mean: 3.9, Median: 3	3.8	Y
Pebody et al 2011³⁶	UK	Apr 09 – Jun 09	259	1046	Case ascertained	Y	RT-PCR	RT-PCR	N	8.3%	ARI, FARI	16%,11%	7	n/a	4.3	N
Pedroni et al 2010³⁷	Chile	Jun 09	57	302	Case ascertained	N	RT-PCR	FARI	N	37%	n/a	n/a	14	Mean: 3.6, Median: 3	3.3	N
Savage et al 2011³⁸	Ontario, Canada	Apr 09 – Jun 09	87	353	Case ascertained	N	RT-PCR	ARI	N	20%	FARI	10%	14	Median: 3	n/a	N
Sikora et al 2010³⁹	Alberta, Canada	Apr 09 – Jun 09	87	349	Case ascertained	N	RT-PCR	FARI	N	30%	n/a	n/a	14	n/a	4.0	N
Simmerman et al 2011⁴⁰	Bangkok, Thailand	Apr 09 – Aug 09	348	1233	Case ascertained	N	RT-PCR	RT-PCR	Y	21%	FARI	14%	7	Mean: 3.32, Median: 2.94	n/a	Y
Suess et al 2010⁴¹	Germany	Apr 09 – Aug 09	36	119	Case ascertained	N	RT-PCR	RT-PCR	Y	18%	n/a	n/a	8	Mean: 2.6, Median: 3	n/a	N
Sugimoto et al 2011⁴²	Washington, USA	May 09 – Jun 09	41	178	Cohort	Y	RT- PCR/FARI	FARI	N	5.9%	n/a	n/a	7	n/a	n/a	N
van Boven et al 2010⁴³	Netherlands	Apr 09 – Jun 09	47	156	Case ascertained	N	RT-PCR	RT-PCR	N	8.3%	n/a	n/a	7	n/a	n/a	N
van Gemert et al 2011⁴⁴	Victora, Australia	May 09 – Jun 09	36	167	Retrospective cross- sectional	N	RT-PCR	FARI	N	15%	n/a	n/a	9	Median: 2	3.1	N

One study (Jackson et al²⁶) was not included in this table because it provided only supplementary serologic data of a previous study (France et al²⁴). Data are included in the main text.

Case ascertained means that index cases were identified through symptom screening or laboratory confirmation; Cohort, index cases were identified from specific populations (e.g. camps, schools, etc) and households without index cases were also followed up

Studies in which it would have been possible for more than one person in a household to be identified as index case (i.e. identification of potential co-primary cases).

RT-PCR indicates respiratory specimen positive for influenza by reverse transcription polymerase chain reaction; ARI, acute respiratory illness; FARI, febrile acute respiratory illness; primary SIR, secondary infection risk based on primary outcome; secondary SIR, secondary infection risk based on secondary outcome; Y, yes; N, no; n/a: not applicable.