Outbreaks of bacterial diseases in Vietnam follow distinct temporal trends and seasonal patterns, according to a Fogarty study published recently in Environmental Health Perspectives. While climate plays a role, the analysis suggests it does not appear to be an important factor influencing the timing of outbreaks.
Water-borne diseases such as dysentery, typhoid fever and cholera are significant health concerns in Vietnam, a densely populated country of approximately 85 million people. To better understand their epidemiology, Dr. Mark A. Miller, Director of Fogarty's Division of International Epidemiology and Population Studies, and his research team determined temporal trends, seasonal patterns and climatic factors associated with high risk periods in eight regions across Vietnam.
By identifying peak periods of disease, the researchers hope to help focus local interventions. The team quantified monthly cases and incidence rates for each region from national surveillance data from 1991 to 2001. They found, on average, the highest incidence rates of dysentery occurred between April and September, and that cholera spiked between May and November. All disease outbreaks occurred earlier in the south than in the north. Peak periods of disease in the southern region coincided with the onset of the wet season, the study showed.
While climatic associations were not strong, distinct climatic differences were evident between the high- and low-disease periods, with hotter, wetter, and more humid conditions associated with an increased incidence of disease. Poor socioeconomic conditions likely play a more important role than climate, the authors conclude. Acknowledging that climate is only one cause of disease outbreaks, the researchers suggest that seasonal changes help define risk periods and may provide some clues into the timing of outbreaks.
Temporal trends and climatic factors associated with bacterial enteric diseases in Vietnam, 1991-2001. Kelly-Hope LA, Alonso WJ, Thiem VD, Canh DG, Anh DD, Lee H, Miller MA. Environ Health Prospect. 2008
To learn more, visit: http://www.ehponline.org/docs/2007/9658/abstract.html.