Table 1 Age and sex distribution of subjects in different study groups at various time points

Pre-pandemic

January 2005 - March 2009

All

222*

115

102

< 20

64 (28.8)

45 (39.1)

18 (17.6)

20-39

22 (9.9)

16 (13.9)

6 (5.9)

40-59

47 (21.2)

23 (20.0)

24 (23.5)

≥60

85 (38.3)

31 (27.0)

54 (52.9)

NA

4 (1.8)

0 (0.0)

0 (0.0)

Hospital staff

August 2009

All

495

276

219

20-39

317 (64.0)

186 (67.4)

131 (59.8)

40-59

173 (34.9)

88 (31.9)

85 (38.8)

NA

5 (1.0)

2 (0.7)

3 (1.4)

October 2009

All

524

250

274

20-39

295 (56.3)

154 (61.6)

141 (51.5)

40-59

225 (42.9)

94 (37.6)

131 (47.8)

NA

4 (0.8)

2 (0.8)

2 (0.7)

November 2009

All

385

183

202

20-39

294 (76.4)

159 (86.9)

135 (66.8)

40-59

86 (22.3)

23 (12.6)

63 (31.2)

NA

5 (1.3)

1 (0.5)

4 (2.0)

General practitioners

August 2009

All

385

244

141

20-39

148 (38.4)

85 (34.8)

63 (44.7)

40-59

200 (51.9)

131 (53.7)

69 (48.9)

≥60

33 (8.6)

26 (10.7)

7 (5.0)

NA

4 (1.0)

2 (0.8)

2 (1.4)

November 2009

All

278

213

65

20-39

132 (47.5)

98 (46.0)

34 (52.3)

40-59

123 (44.2)

98 (46.0)

25 (38.5)

≥60

21 (7.6)

15 (7.0)

6 (9.2)

NA

2 (0.7)

2 (0.9)

0 (0.0)

December 2009

All

225

156

69

20-39

167 (74.2)

111 (71.2)

56 (81.2)

40-59

52 (23.1)

39 (25.0)

13 (18.8)

≥60

6 (2.7)

6 (3.8)

0 (0.0)

School staff

August 2009

All

348

97

251

20-39

152 (43.7)

34 (35.1)

118 (47.0)

40-59

178 (51.1)

54 (55.7)

124 (49.4)

≥60

6 (1.7)

4 (4.1)

2 (0.8)

NA

12 (3.4)

5 (5.2)

7 (2.8)

September 2009

All

177

27

150

20-39

100 (56.5)

17 (63.0)

83 (55.3)

40-59

67 (37.9)

7 (25.9)

60 (40.0)

≥60

5 (2.8)

0 (0.0)

5 (3.3)

NA

5 (2.8)

3 (11.1)

2 (1.3)

School children

September 2009

All

(< 20)

2527

755

1772

Railway commuters

September 2009

All

225

150

75

20-39

40 (17.8)

22 (14.7)

18 (24.0)

40-59

49 (21.8)

37 (24.7)

12 (16.0)

≥60

1 (0.4)

1 (0.7)

0 (0.0)

NA

135 (60.0)

90 (60.0)

45 (60.0)

Office staff

September 2009

All

233

175

58

20-39

152 (65.2)

104 (59.4)

48 (82.8)

40-59

78 (33.5)

69 (39.4)

9 (15.5)

NA

3 (1.3)

2 (1.1)

1 (1.7)

Slum-dwellers

September 2009

All

651

292

359

< 20

252 (38.7)

139 (47.6)

113 (31.5)

20-39

248 (38.1)

95 (32.5)

153 (42.6)

40-59

96 (14.7)

33 (11.3)

63 (17.5)

≥60

27 (4.1)

13 (4.5)

14 (3.9)

NA

28 (4.3)

12 (4.1)

16 (4.5)

General population

October

2009

All

2520

1138

1382

< 20

877 (34.8)

471 (41.4)

406 (29.4)

20-39

885 (35.1)

335 (29.4)

550 (39.8)

40-59

515 (20.4)

213 (18.7)

302 (21.9)

≥60

226 (9.0)

107 (9.4)

119 (8.6)

NA

17 (0.7)

12 (1.1)

5 (0.4)

PCR-confirmed cases

September - October 2009

All

65

30

35

< 20

45 (69.2)

19 (63.3)

26 (74.3)

20-39

14 (21.5)

7 (23.3)

7 (20.0)

40-59

3 (4.6)

2 (6.7)

1 (2.9)

NA

3 (4.6)

2 (6.7)

1 (2.9)

Household contacts

September-October 2009

All

195

84

111

< 20

43 (22.1)

21 (25.0)

22 (19.8)

20-39

75 (38.5)

34 (40.5)

41 (36.9)

40-59

47 (24.1)

21 (25.0)

26 (23.4)

≥60

19 (9.7)

5 (6.0)

14 (12.6)

NA

11 (5.6)

3 (3.6)

8 (7.2)