Data Management and Analysis
The demographic, clinical, and associated factors are described for cholera cases and all enrolled diarrhea cases. We also compared data from patients with cholera with non–cholera cases by a 2-sample test of proportions. We estimated risk ratios for different potential factors associated with cholera assumed as clusters using log-binomial regression with generalized estimating equations (GEEs) accounting for robust standard errors. For the GEE models, we used an independent correlation structure, accounting for individual clustering within each site. A univariate analysis was conducted using GEE to examine the risk of cholera for factors including age, gender, and exposure histories. Based on previous literature review, we then constructed a multivariable log-binomial regression model and performed inference with GEEs.
For the geographic location of cholera in Bangladesh, we selected geographic midpoints in the country and defined 4 zones: Northeast (NE), Northwest (NW), Southeast (SE), and Southwest (SW). Within each zone, we reported the percentage of cholera-positive cases among the patients with diarrhea. To describe the catchment area of the sentinel sites and healthcare- seeking behavior of the patients with diarrhea, we calculated the distance of each enrolled patient’s home location to the hospital. We then calculated the cumulative probability distribution of attending a sentinel site by distance in kilometers (km) for cholera and non–cholera cases and also by disease severity based on dehydration status.
RESULTS
Between 4 May 2014 and 31 June 2018, we captured a total of 210 679 cases of diarrhea and 26 221 were enrolled; 46% were female. Among children under 5 years of age (45.6% of those tested), 86.7% (10 374/11 968) were younger than 2 years and 13.3% (1594/11 968) were aged 2–4 years old. Of children 5 years and older in age (54.4% of those tested), 9.5% (1350/14 253) were 5–17 years, 63.5% (9044/14 253) were 18–45 years, and 27% (3859/14 253) were 46 years or older. Of those enrolled, 62.8% had no formal schooling, which included children and those who did not complete primary school (class 5); 23% of patients were housewives and 8.6% were service holders; among those who were older (≥15 years), 45% were housewives and 17% were service holders. The majority of patients reported some (63.9%) or severe (14.2%) dehydration. Vomiting (67.3%), abdominal cramps (61.6%), and fever (60.5%) were also reported. Twenty-eight percent of patients had eaten food from roadside vendors, 11% had eaten food in large gatherings, and 14% had neighbors with diarrhea in the week prior to illness (Supplementary Table 1).
Supplementary Table 1. Overall distribution of demographic, clinical factors and history of exposures of acute diarhea cases enrolled in the surveillance sites by divisions, May 2014 - June 2018, Bangladesh
Characteristics | Overall n(%), N=26221 | Dhaka n(%), N=6251 | Chittagong n(%), N=4660 | Barisal n(%),N=2785 | Sylhet n(%), N=2737 | Khulna n(%), N=5969 | Rajshahi n(%), N=2110 | Rangpur n(%), N=1709 |
Age (years) |
<5 | 11968 (45.6) | 2449 (39.2) | 1099 (23.6) | 1511 (54.3) | 1588 (58.0) | 2703 (45.3) | 1087 (51.5) | 1531 (89.6) |
5-17 | 1350 (5.2) | 408 (6.5) | 297 (6.4) | 134 (4.8) | 96 (3.5) | 311 (5.2) | 87 (4.1) | 17 (1.0) |
18-45 | 9044 (34.5) | 2393 (38.3) | 2450 (52.6) | 724 (26.0) | 756 (27.6) | 1985 (33.3) | 623 (29.5) | 113 (6.6) |
>46 | 3859 (14.7) | 1001 (16.0) | 814 (17.5) | 416 (14.9) | 297 (10.9) | 970 (16.3) | 313 (14.8) | 48 (2.8) |
Sex (Male) | 14181 (54.1) | 3420 (54.7) | 2319 (49.8) | 1464 (52.6) | 1524 (55.7) | 3190 (53.4) | 1216 (57.6) | 1048 (61.3) |
Education |
No formal schooling (child, not completed primary) | 16453 (62.8) | 3410 (54.6) | 2117 (45.4) | 1838 (66.0) | 2081 (76.0) | 4007 (67.1) | 1457 (69.1) | 1543 (90.3) |
Primary | 6623 (25.3) | 1857 (29.7) | 1785 (38.3) | 567 (20.4) | 549 (20.1) | 1343 (22.5) | 443 (21.0) | 79 (4.6) |
Secondary and above | 3145 (12.0) | 984 (15.7) | 758 (16.3) | 380 (13.6) | 107 (3.9) | 619 (10.4) | 210 (9.9) | 87 (5.1) |
Occupation |
Service holder | 2261 (8.6) | 913 (14.6) | 845 (18.1) | 67 (2.4) | 73 (2.8) | 278 (4.7) | 71 (3.4) | 14 (0.8) |
Agricultural worker | 1213 (4.6) | 147 (2.4) | 112 (2.4) | 93 (3.3) | 148 (5.4) | 524 (8.8) | 157 (7.4) | 32 (1.9) |
Businessman | 1199 (4.6) | 356 (5.7) | 274 (5.9) | 103 (3.7) | 48 (1.8) | 294 (4.9) | 110 (5.2) | 14 (0.8) |
Housewife | 5905 (22.5) | 1430 (22.9) | 1279 (27.5) | 649 (23.3) | 539 (19.7) | 1458 (24.4) | 462 (21.9) | 88 (5.2) |
Day laborer | 838 (3.2) | 205 (3.3) | 289 (6.2) | 45 (1.6) | 86 (3.1) | 128 (2.1) | 82 (3.9) | 3 (0.2) |
Students & unemployed | 2510 (9.6) | 624 (9.9) | 670 (14.4) | 299 (10.7) | 229 (8.4) | 541 (9.1) | 124 (5.9) | 23 (1.4) |
Baby/Child (up to 10 years) | 12132 (46.3) | 2507 (40.1) | 1150 (24.7) | 1523 (54.7) | 1597 (58.4) | 2725 (45.7) | 1099 (52.1) | 1531 (89.6) |
Others | 163 (0.6) | 69 (1.1) | 41 (0.9) | 6 (0.2) | 17 (0.6) | 21 (0.4) | 5 (0.2) | 4 (0.2) |
Clinical Symptoms | | | | | | | | |
Fever | 15871 (60.5) | 4584 (73.0) | 2818 (60.0) | 1009 (36.2) | 2022 (74.0)) | 3251 (54.7) | 1132 (53.7) | 1055 (61.7) |
Vomiting | 17658 (67.3) | 5037 (80.6) | 3468 (74.0) | 2058 (74.0) | 1221 (44.6) | 3166 (53.0) | 1452 (69.0) | 1256 (73.5) |
Dehydration status |
None | 5752 (21.9) | 838 (13.0) | 1211 (26.0) | 1034 (37.1) | 1149 (41.9) | 1106 (18.5) | 176 (8.3) | 238 (13.9) |
Some | 16742 (63.9) | 3964 (63.4) | 2769 (59.4) | 1654 (59.4) | 1171 (42.8) | 4760 (79.8) | 1698 (79.8) | 726 (42.5) |
Severe | 3727 (14.2) | 1449 (23.2) | 680 (14.6) | 97 (3.5) | 417 (15.2) | 103 (1.7) | 236 (1.7) | 745 (43.6) |
Abdominal cramp | 16155 (61.6) | 4789 (77.0) | 3420 (73.4) | 1842 (66.0) | 1185 (43.0) | 3192 (53.5) | 1579 (75.0) | 148 (9.0) |
Behavioral Exposures | | | | | | | | |
Water treatment habit (Boiled) | 2071 (7.9) | 1148 (18.0) | 336 (7.0) | 302 (11.0) | 59 (2.0) | 90 (2.0) | 133 (6.0) | 3 (0.2) |
Taken Food from road side vendors | 7225 (28.0) | 936 (15.3) | 1503 (32.3) | 643 (23.1) | 848 (30.9) | 2079 (34.8) | 1199 (56.8) | 17 (1.0) |
Taken of food from large gatherings | 2875 (11.0) | 333 (5.3) | 1076 (23.1) | 110 (3.9) | 302 (11.0) | 508 (8.5) | 537 (25.5) | 9 (0.5) |
HH members suffered from diarrhea during last week | 1665 (6.4) | 285 (4.6) | 736 (15.8) | 138 (4.9) | 63 (2.3) | 231 (3.9) | 162 (7.7) | 50 (2.9) |
Neighbors had diarrhea during last week | 3579 (13.7) | 336 (5.4) | 895 (19.2) | 1386 (49.8) | 301 (11.0) | 416 (6.9) | 224 (10.6) | 21 (1.2) |