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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

The monthly number of shigellosis/dysentery, typhoid fever, and cholera cases reported in Vietnam during 1991–2001.
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f2-ehp0116-000007: The monthly number of shigellosis/dysentery, typhoid fever, and cholera cases reported in Vietnam during 1991–2001.

Mentions: The monthly numbers of shigellosis/dysentery, typhoid fever, and cholera cases reported in Vietnam during 1991–2001 are shown in Figure 2. Shigellosis/dysentery was the most prevalent disease and increased approximately 2.5 times during the study period, with 16,976 cases (annual IR of 25.3 per 100,000) reported in 1991 compared with 46,292 cases (IR, 58.8) in 2001. The annual number of typhoid fever cases was similar at the beginning (7,592 cases; IR, 11.3) and end (9,614 cases; IR, 12.2) of the study period; however, there was a 3-fold increase during 1994 to 1997, with an average of 24,553 cases (IR, 33.8) reported annually. Overall, there were fewer cholera cases, which appeared episodically during 1991–1996, with four main peaks in May 1992 (1,851 cases; IR, 2.7), August–September 1993 (943–1,054 cases; IR, 1.4–1.5), May 1994 (1,127 cases; IR, 1.6), and June–July 1995 (1,097–1,492 cases; IR, 1.5–2.1). From January 1997 onward, the number of cholera cases reported nationwide decreased significantly, with only two minor peaks reported in January–February 1999 (188 cases; IR, 0.25) and September–October 2000 (166 cases; IR, 0.21).


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)

The monthly number of shigellosis/dysentery, typhoid fever, and cholera cases reported in Vietnam during 1991–2001.
© Copyright Policy - public-domain
Related In: Results  -  Collection

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

f2-ehp0116-000007: The monthly number of shigellosis/dysentery, typhoid fever, and cholera cases reported in Vietnam during 1991–2001.
Mentions: The monthly numbers of shigellosis/dysentery, typhoid fever, and cholera cases reported in Vietnam during 1991–2001 are shown in Figure 2. Shigellosis/dysentery was the most prevalent disease and increased approximately 2.5 times during the study period, with 16,976 cases (annual IR of 25.3 per 100,000) reported in 1991 compared with 46,292 cases (IR, 58.8) in 2001. The annual number of typhoid fever cases was similar at the beginning (7,592 cases; IR, 11.3) and end (9,614 cases; IR, 12.2) of the study period; however, there was a 3-fold increase during 1994 to 1997, with an average of 24,553 cases (IR, 33.8) reported annually. Overall, there were fewer cholera cases, which appeared episodically during 1991–1996, with four main peaks in May 1992 (1,851 cases; IR, 2.7), August–September 1993 (943–1,054 cases; IR, 1.4–1.5), May 1994 (1,127 cases; IR, 1.6), and June–July 1995 (1,097–1,492 cases; IR, 1.5–2.1). From January 1997 onward, the number of cholera cases reported nationwide decreased significantly, with only two minor peaks reported in January–February 1999 (188 cases; IR, 0.25) and September–October 2000 (166 cases; IR, 0.21).

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