Spatiotemporal Patterns of Anthrax, Vietnam, 1990-2015

Abstract

Anthrax is a priority zoonosis for control in Vietnam. The geographic distribution of anthrax remains to be defined, challenging our ability to target areas for control. We analyzed human anthrax cases in Vietnam to obtain anthrax incidence at the national and provincial level. Nationally, the trendline for cases remained at ≈61 cases/year throughout the 26 years of available data, indicating control efforts are not effectively reducing disease burden over time. Most anthrax cases occurred in the Northern Midlands and Mountainous regions, and the provinces of Lai Chau, Dien Bien, Lao Cai, Ha Giang, Cao Bang, and Son La experienced some of the highest incidence rates. Based on spatial Bayes smoothed maps, every region of Vietnam experienced human anthrax cases during the study period. Clarifying the distribution of anthrax in Vietnam will enable us to better identify risk areas for improved surveillance, rapid clinical care, and livestock vaccination campaigns.

Keywords: Bacillus anthracis; Vietnam; anthrax; bacteria; epidemiology; incidence; mortality rate; spatiotemporal patterns; vaccine-preventable diseases; zoonoses.

Figure 1

Regions of Vietnam. Current reports of anthrax in Vietnam are concentrated in the Northern Midlands and Mountainous region (inset), especially in 6 provinces bordering or close to China: Dien Bien, Lai Chau, Lao Cai, Ha Giang, Son La, and Cao Bang.

Figure 2

National human anthrax cases and incidence per 10,000 persons per year in Vietnam, 1990‒2015. Gray arrows indicate deaths.

Figure 3

Percentage population change in the communes of Vietnam during 1990‒2015. Light blue, dark blue, and green values indicate communes that had population decreases, and yellow, orange, and red values indicate communes that had population growth.

Figure 4

Choropleth maps of spatial Bayes smoothed human anthrax incidence rates in provinces of Vietnam. The years are not necessarily those with the highest anthrax incidence rates but those with the most widespread range of anthrax. Although anthrax incidence rates were highest in the northern provinces, they were not limited to those provinces.