Characteristic	FRI cases (N = 7743)	Percent	Non-FRI study controls (N = 1247)	Percent	P-valuea
Age:
Mean (SD)	20.8	(3.12)	21.0	(2.62)	<0.001b
Range	17-60		18-55
Gender:
Male	7723	99.7	1246	99.9	0.354
Ethnic groups
Chinese	5834	75.4	972	77.9
Malay	1151	14.9	158	12.7
Indian	510	6.6	88	7.1
Others	248	3.2	29	2.3	0.344
Camp
Non-recruit camp	2186	28.2	827	66.3	<0.001
Recruit camp	5557	71.8	420	33.7
Pre-pdm TIV:
Yes	180	2.3	49	3.9	0.002
Post-pdm TIV:
Yes	2400	31.0	279	22.4	<0.001
Pdm-A(H1N1)V:
Yes	1335	17.2	222	17.8	0.629
Smoking
Non-smoker	5388	69.6	877	70.3
Current-smoker	2094	27.1	346	27.7
Ex-smoker	257	3.3	24	1.9	0.028
Asthma
Yes	1598	20.6	215	17.2	0.004
Heart disease
Yes	83	1.1	15	1.2	0.763
Diabetes
Yes	8	0.1	2	0.2	0.656
Hypertension
Yes	45	0.6	6	0.5	0.700
Travelled to community in last 14 days:
Yes	7670	99.1	1238	99.3	0.548
Travelled to other camp in last 14 days:
Yes	471	6.1	177	14.2	<0.001
Travelled overseas in the last 14 days:
Yes	227	2.9	49	3.9	0.057
Camp stay
Stay-in	6928	89.6	1018	81.6	<0.001