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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

Vietnam and its eight regions: Northeast [NE; 8,524,800 (average population for 1996)], Northwest (NW; 2,112,900), Red River Delta (RRD; 16,331,800), North Central Coast (NCC; 9,696,100), South Central Coast (SCC; 6,287,300), Southeast (SE; 10,947,300), Central Highlands (CH; 3,563,000), and Mekong River Delta (MRD; 15,693,500).
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f1-ehp0116-000007: Vietnam and its eight regions: Northeast [NE; 8,524,800 (average population for 1996)], Northwest (NW; 2,112,900), Red River Delta (RRD; 16,331,800), North Central Coast (NCC; 9,696,100), South Central Coast (SCC; 6,287,300), Southeast (SE; 10,947,300), Central Highlands (CH; 3,563,000), and Mekong River Delta (MRD; 15,693,500).

Mentions: Vietnam is a narrow, densely populated country in southeastern Asia bordering China, Laos, and Cambodia (General Statistics Office of Vietnam 2005). It has approximately 85 million people living in an area of 330,000 km2, with > 3,000 km of coastline. In the south the climate is tropical, whereas in the north, the two main seasons are a warm, wet summer and a cool, humid winter. The terrain is diverse with low, flat deltas in the south and north; highlands in the center; and hilly mountains in the northwestern region. Vietnam experiences occasional typhoons with extensive flooding, especially in the southern Mekong River Delta. Vietnam currently is divided into 64 provinces and eight agro-ecologic regions (Figure 1): Northeast, Northwest, Red River Delta, North Central Coast, South Central Coast, Central Highlands, Southeast, and Mekong River Delta. We used the eight geographic regions as the basis of our temporal and climatic analyses.


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)

Vietnam and its eight regions: Northeast [NE; 8,524,800 (average population for 1996)], Northwest (NW; 2,112,900), Red River Delta (RRD; 16,331,800), North Central Coast (NCC; 9,696,100), South Central Coast (SCC; 6,287,300), Southeast (SE; 10,947,300), Central Highlands (CH; 3,563,000), and Mekong River Delta (MRD; 15,693,500).
© Copyright Policy - public-domain
Related In: Results  -  Collection

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

f1-ehp0116-000007: Vietnam and its eight regions: Northeast [NE; 8,524,800 (average population for 1996)], Northwest (NW; 2,112,900), Red River Delta (RRD; 16,331,800), North Central Coast (NCC; 9,696,100), South Central Coast (SCC; 6,287,300), Southeast (SE; 10,947,300), Central Highlands (CH; 3,563,000), and Mekong River Delta (MRD; 15,693,500).
Mentions: Vietnam is a narrow, densely populated country in southeastern Asia bordering China, Laos, and Cambodia (General Statistics Office of Vietnam 2005). It has approximately 85 million people living in an area of 330,000 km2, with > 3,000 km of coastline. In the south the climate is tropical, whereas in the north, the two main seasons are a warm, wet summer and a cool, humid winter. The terrain is diverse with low, flat deltas in the south and north; highlands in the center; and hilly mountains in the northwestern region. Vietnam experiences occasional typhoons with extensive flooding, especially in the southern Mekong River Delta. Vietnam currently is divided into 64 provinces and eight agro-ecologic regions (Figure 1): Northeast, Northwest, Red River Delta, North Central Coast, South Central Coast, Central Highlands, Southeast, and Mekong River Delta. We used the eight geographic regions as the basis of our temporal and climatic analyses.

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