Table 1.
Comparison of Cholera in the Ganges Delta and Many Countries in Africa
| Feature | Ganges Delta | Africa |
|---|---|---|
| Endemicity | Cholera cases are reported every year, throughout the year | Sporadic outbreaks |
| Seasonality | Different regions within the country have peak rates depending on season The seasonal peaks are consistent, year to year |
Some countries have a strong seasonality (eg, Burundi), but outbreaks may occur during different seasons |
| Geographic consistency | The same areas are affected from year to year | Hotspots identified but variable from year to year for most countries |
| Outbreaks | In Bangladesh, cases never stop; thus, it is difficult to define the end of an outbreak | Cholera occurs during well-defined outbreaks with a clear start and end |
| Risk by age group | The highest rates occur among young children aged 2–5 y | Similar rates across the age groups |
| Risk by sex | Higher number of cases in young boys compared to girls Higher numbers in women aged 15–45 y compared to men |
Similar to Asia, but needs more study |
| Asymptomatic infections | Most infections are asymptomatic or mildly symptomatic | Needs further study |
| Biological susceptibility to severe disease | Persons with hypochlorhydria, with blood group O and possibly Lewis blood group Le(a+ b−) have higher rates | Not known |
| Methods to monitor disease burden | Sentinel surveillance at preselected sites is efficient when monitoring rates of disease and disease burden | Sentinel surveillance has limited value, but broad-based detection with rapid reporting is needed |
| Relation between endemic disease and vaccine effectiveness | Preexisting immunity affects vaccine response Vaccine response affects response to future natural exposures Protection results from combination of vaccine and natural exposure |
Vaccine stimulates immune protection, but natural exposure has limited effect |
| Detection of Vibrio cholerae in environmental water | V. cholerae can be identified frequently in ponds and rivers as well as drinking water at the source and in the household |
V. cholerae is rarely detected More studies are needed to determine optimal methods |
| Viable but not culturable (VBNC) V. cholerae | VBNC forms of V. cholerae can be identified throughout the year in pond water | Not yet studied |
| Genetic characteristics of V. cholerae | Multiple genotypes circulating in the country | A single genotype, or few types spread through an area |