Temporal trends and climatic factors associated with bacterial enteric diseases in Vietnam, 1991-2001.
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.
Kelly-Hope
Louise A
LA
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
Alonso
Wladimir J
WJ
Thiem
Vu Dinh
VD
Canh
Do Gia
DG
Anh
Dang Duc
DD
Lee
Hyejon
H
Miller
Mark A
MA
D002980:Climate; D016905:Gram-Negative Bacterial Infections / Q000453:epidemiology* / Q000209:etiology; D006801:Humans; D015994:Incidence; D012307:Risk Factors; D012621:Seasons; D013997:Time Factors; D014744:Vietnam / Q000453:epidemiology