Spatiotemporal analysis of brucellosis incidence in Iran from 2011 to 2014 using GIS.

OBJECTIVE

To investigate the distribution and trends associated with brucellosis incidence rates in Iran from 2011 to 2014.

METHODS

The reported incidence rates of brucellosis for the years 2011-2014 were collected and entered into GIS 10.1. The Cochran-Armitage test for linear trends, choropleth maps, hot-spot analysis, and high-low clustering analysis were used to investigate patterns of the disease over the study period and by season, and to identify high-risk areas and any clustering of the disease. The significance level was set at p<0.05.

RESULTS

A total of 68493 cases of brucellosis were reported during the study period, giving an average brucellosis incidence rate for this period of 38.67/100000. In 2011, the highest rate of brucellosis was observed in Koohrang County of Chaharmahal-Bakhtiari Province, with 317/100 000. In the subsequent years, 2012-2014, Charuymaq County of East-Azerbaijan Province had incidence rates of 384, 534, and 583/100000, respectively. However, the incidence rate of the disease did not follow a linear trend (p<0.001). The maximum and minimum incidence rates of the disease occurred in mid-summer and mid-winter, respectively. The results of the hot-spot analysis showed that the distribution of the disease was highest in the mountainous areas of Iran, particularly along the Zagros mountain range and in most cities near the Zagros Mountains (p<0.01). In addition, the cluster analysis showed a clustering pattern in these high incidence areas (p<0.01).

CONCLUSIONS

There were significant differences in the geographic distribution of brucellosis, with the incidence rates being highest in most of the cities in the west and north-west of the country. The incidence of this disease also increased during the summer. It is important to take these patterns into account when allocating resources to combat this disease and to ensure that health programs and other interventions focus on the areas of greatest need.