Although the numbers of patients with diarrhea were generally constant over time, there was a distinct pattern in the seasonality of cholera (Figure 2A). A biannual cholera peak was present across all sites in the pre–monsoon (March–June) and post–monsoon (September–October) seasons (Figure 2B). In the NW and SW regions, we observed higher cholera positivity during the postmonsoon peak, while in the NE and SE regions the premonsoon seasonal peak predominated (Figure 2C).

Cholera-associated Factors

In the GEE, we found that the risk of cholera among patients with diarrhea younger than 5 years of age was lower than in other age groups, with 5- to 17-year-olds having a 5.1-fold increased risk of cholera (95% confidence interval [CI], 2.9– 8.8), 18- to 45-year-olds having a 3.8-fold increased risk of cholera (95% CI, 2.1–6.7), and those aged 46 years or older having a 2.7-fold increased risk of cholera (95% CI, 1.5–4.9) compared with those less than 5 years of age. Being an agricultural worker, businessman, housewife, or student was significantly associated with a decreased risk of being a confirmed cholera case compared with being a service holder. Patients with diarrhea who had neighbors with diarrhea in the week prior to illness had a 1.6 times greater risk of cholera (95% CI, 1.2–2.1) (Table 2).
Table 2: Analysis of behaviors and exposure risk factors of confirmed V. cholerae culture positive cases using a generalized estimation equation for all surveillance sites
Characteristics cRR (95% CI) aRR (95% CI)
Age (years)
<5 (ref) 1.0 1.0
5-17 6.3 (4.6, 8.8) 5.1 (2.9, 8.8)
18-45 4.7 (3.7, 6.2) 3.8 (2.1, 6.7)
>46 3.2 (2.4, 4.2) 2.7 (1.5, 4.9)
Sex (Male)* 0.9 (0.9, 1.1) -
Education
No formal schooling (child, not completed primary) (ref) 1.0 1.0
Primary 2.7 (2.2, 3.4)) 1.1 (0.9, 1.3)
Secondary and above 2.4 (1.8, 3.1) 0.9 (0.7, 1.1)
Occupation
Service holder (ref) 1.0 1.0
Agricultural worker 0.5 (0.4, 0.8) 0.6 (0.4, 0.8)
Businessman 0.7 (0.5, 0.9) 0.7 (0.6, 0.9)
Housewife 0.6 (0.5, 0.8) 0.6 (0.5, 0.7)
Day laborer 1.2 (0.9, 1.6) 1.2 (0.9, 1.5)
Students & unemployed 0.8 (0.6, 1.0) 0.7 (0.5, 0.9)
Baby/Child (up to 10 years) 0.2 (0.1, 0.3) 0.6 (0.3, 0.9)
Others 0.5 (0.2, 1.1) 0.5 (0.2, 1.1)
Behavioral Exposures*    
Water treatment habit (Boiled) 1.0 (0.8, 1.4) 1.2 (0.9, 1.5)
Taken Food from road side vendors 1.1 (0.9, 1.5) 0.9 (0.8, 1.1)
Taken of food from large gatherings 1.3 (1.0, 1.8) 1.0 (0.8, 1.2)
HH members suffered from diarrhea during last week 1.6 (1.2, 2.1) 1.2 (0.9, 1.5)
Neighbors had diarrhea during last week 1.3 (0.9, 1.9) 1.6 (1.2, 2.1)