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Temporal trends and climatic factors associated with bacterial enteric diseases in Vietnam, 1991-2001.

Kelly-Hope LA, Alonso WJ, Thiem VD, Canh do G, Anh DD, Lee H, Miller MA - Environ. Health Perspect. (2008)

Bottom Line: Cholera was mostly epidemic along the central coast between May and November (0.07-2.7), and then decreased dramatically nationwide from 1997 onward.Significant climate differences were found only between high- and low-disease periods.Climate plays a role in defining high- and low-disease periods, but it does not appear to be an important factor influencing outbreaks.

View Article: PubMed Central - PubMed

Affiliation: Division of International Epidemiology and Population Studies, Fogarty International Center, National Institutes of Health, Department of Health and Human Services, Bethesda, MD 20892, USA. kellyhopel@mail.nih.gov

ABSTRACT

Objective: In Vietnam, shigellosis/dysentery, typhoid fever, and cholera are important enteric diseases. To better understand their epidemiology, we determined temporal trends, seasonal patterns, and climatic factors associated with high risk periods in eight regions across Vietnam.

Methods: We quantified monthly cases and incidence rates (IR) for each region from national surveillance data (1991-2001). High- and low-disease periods were defined from the highest and lowest IRs (1 SD above and below the mean) and from outbreaks from positive outliers (4 SDs higher in 1 month or 2 SDs higher in > or = 2 consecutive months). We used general linear models to compare precipitation, temperature, and humidity between high- and low-risk periods.

Results: Shigellosis/dysentery was widespread and increased 2.5 times during the study period, with the highest average IRs found between June and August (2.1/100,000-26.2/100,000). Typhoid fever was endemic in the Mekong River Delta and emerged in the Northwest in the mid-1990s, with peaks between April and August (0.38-8.6). Cholera was mostly epidemic along the central coast between May and November (0.07-2.7), and then decreased dramatically nationwide from 1997 onward. Significant climate differences were found only between high- and low-disease periods. We were able to define 4 shigellosis/dysentery, 14 typhoid fever, and 8 cholera outbreaks, with minimal geotemporal overlap and no significant climatic associations.

Conclusions: In Vietnam, bacterial enteric diseases have distinct temporal trends and seasonal patterns. Climate plays a role in defining high- and low-disease periods, but it does not appear to be an important factor influencing outbreaks.

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Related in: MedlinePlus

Average monthly shigellosis/dysentery, typhoid fever, and cholera incidence rates per 100,000 population in eight regions of Vietnam. Note the different scale for shigellosis in the Central Highlands.
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f4-ehp0116-000007: Average monthly shigellosis/dysentery, typhoid fever, and cholera incidence rates per 100,000 population in eight regions of Vietnam. Note the different scale for shigellosis in the Central Highlands.

Mentions: Overall, we found distinct seasonal variations in each region, as shown by the average monthly IRs in Figure 4. Shigellosis/dysentery rates peaked in the northern regions of the country (Northeast, Northwest, Red River Delta, North Central Coast) between June and August (IR range, 2.1–7.8), and in the southern regions (South Central Coast, Central Highlands, Southeast, Mekong River Delta) between May and July (IR range, 8.2–26.2); the highest monthly IR occurred in the Central Highlands in June (IR, 26.2). Typhoid fever rates peaked in the northern regions between May and September (IR range, 0.38–5.2) and in the southern regions between April and July (IR range, 0.43–8.6); the highest monthly IRs occurred in the Northwest in July (IR, 5.2) and the Mekong River Delta in April (IR, 8.6). Cholera rates peaked in the northern regions between May and November (IR range, 0.07–2.7) and in the southern regions between May and July (IR range, 0.51–2.6). No cholera cases were reported in the Northwest, whereas the highest monthly IRs occurred in the North Central Coast in May (IR, 2.7) and in the South Central Coast in July (IR, 2.6).


Temporal trends and climatic factors associated with bacterial enteric diseases in Vietnam, 1991-2001.

Kelly-Hope LA, Alonso WJ, Thiem VD, Canh do G, Anh DD, Lee H, Miller MA - Environ. Health Perspect. (2008)

Average monthly shigellosis/dysentery, typhoid fever, and cholera incidence rates per 100,000 population in eight regions of Vietnam. Note the different scale for shigellosis in the Central Highlands.
© Copyright Policy - public-domain
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2199291&req=5

f4-ehp0116-000007: Average monthly shigellosis/dysentery, typhoid fever, and cholera incidence rates per 100,000 population in eight regions of Vietnam. Note the different scale for shigellosis in the Central Highlands.
Mentions: Overall, we found distinct seasonal variations in each region, as shown by the average monthly IRs in Figure 4. Shigellosis/dysentery rates peaked in the northern regions of the country (Northeast, Northwest, Red River Delta, North Central Coast) between June and August (IR range, 2.1–7.8), and in the southern regions (South Central Coast, Central Highlands, Southeast, Mekong River Delta) between May and July (IR range, 8.2–26.2); the highest monthly IR occurred in the Central Highlands in June (IR, 26.2). Typhoid fever rates peaked in the northern regions between May and September (IR range, 0.38–5.2) and in the southern regions between April and July (IR range, 0.43–8.6); the highest monthly IRs occurred in the Northwest in July (IR, 5.2) and the Mekong River Delta in April (IR, 8.6). Cholera rates peaked in the northern regions between May and November (IR range, 0.07–2.7) and in the southern regions between May and July (IR range, 0.51–2.6). No cholera cases were reported in the Northwest, whereas the highest monthly IRs occurred in the North Central Coast in May (IR, 2.7) and in the South Central Coast in July (IR, 2.6).

Bottom Line: Cholera was mostly epidemic along the central coast between May and November (0.07-2.7), and then decreased dramatically nationwide from 1997 onward.Significant climate differences were found only between high- and low-disease periods.Climate plays a role in defining high- and low-disease periods, but it does not appear to be an important factor influencing outbreaks.

View Article: PubMed Central - PubMed

Affiliation: Division of International Epidemiology and Population Studies, Fogarty International Center, National Institutes of Health, Department of Health and Human Services, Bethesda, MD 20892, USA. kellyhopel@mail.nih.gov

ABSTRACT

Objective: In Vietnam, shigellosis/dysentery, typhoid fever, and cholera are important enteric diseases. To better understand their epidemiology, we determined temporal trends, seasonal patterns, and climatic factors associated with high risk periods in eight regions across Vietnam.

Methods: We quantified monthly cases and incidence rates (IR) for each region from national surveillance data (1991-2001). High- and low-disease periods were defined from the highest and lowest IRs (1 SD above and below the mean) and from outbreaks from positive outliers (4 SDs higher in 1 month or 2 SDs higher in > or = 2 consecutive months). We used general linear models to compare precipitation, temperature, and humidity between high- and low-risk periods.

Results: Shigellosis/dysentery was widespread and increased 2.5 times during the study period, with the highest average IRs found between June and August (2.1/100,000-26.2/100,000). Typhoid fever was endemic in the Mekong River Delta and emerged in the Northwest in the mid-1990s, with peaks between April and August (0.38-8.6). Cholera was mostly epidemic along the central coast between May and November (0.07-2.7), and then decreased dramatically nationwide from 1997 onward. Significant climate differences were found only between high- and low-disease periods. We were able to define 4 shigellosis/dysentery, 14 typhoid fever, and 8 cholera outbreaks, with minimal geotemporal overlap and no significant climatic associations.

Conclusions: In Vietnam, bacterial enteric diseases have distinct temporal trends and seasonal patterns. Climate plays a role in defining high- and low-disease periods, but it does not appear to be an important factor influencing outbreaks.

Show MeSH
Related in: MedlinePlus