The highest incidence of brucellosis is related to 1994 with 512 cases (16%). The average wind speed in 8 years was 1.89. The incidence is the highest at zero total monthly rainfall. Total monthly rainfall was 0 at 444 days (13.9%), which includes most days of study. The minimum temperature was − 1 and the maximum temperature was 30 degrees centigrade. The mean age of the patients was about 38 years.
There is no clear pattern in the number of cases of Brucellosis in the 8 years studied and fluctuations in the incidence of this disease can be seen with three peaks 2015 December, July 2015, June 2014. These results are inconsistent with the results of Lee's study. In the Lee study, the incidence of human Brucellosis in South Korea peaked in September 2006 and has dropped dramatically since then which indicates effective eradication (16). In Rafiemanesh’s study, the incidence of Brucellosis decreased from 2007 to 2016 which indicates an increase in the coverage of prevention programs, especially livestock vaccination(17). These results are inconsistent with the results of the present study.
During the 8 years, in the 2010 year, the lowest number of cases has been reported, followed by an upward trend until 2011. The reason for the rising trend of the disease from 2010 to 2011 may be related to the improvement of the data registration in the country's health system. This result is consistent with Hashtarkhani’s study(18). From 2014 to 2017, there is an upward trend in the number of Brucellosis cases which is inconsistent with Hashtarkhani's study. In the study of Hashtarkhani after 1990, we see a decreasing trend in the incidence of the disease(18). The results of the study show that there are the highest number of infected people in summer and winter seasons. These results are consistent with the results of the Tapak’s study. The results of the Tapak’s study show that hot summers and cold winters make the disease less common while climate moderation in these seasons exacerbates the disease(19). Therefore, the temperate climate of these seasons in Qazvin province increases the number of patients with Brucellosis. Model fit results indicate the negative effect of age and total monthly rainfall on the number of Brucellosis. This result is consistent with the results of Entezari's study. The results of the Entezari's study indicate a negative relationship between rainfall and brucellosis. In fact, as the rainfall decreases, the number of infected people increases(20).
Comparing the coefficients of explanatory variables in two state, the average wind speed is the most important factor in incidence Brucellosis. This result is consistent with the results of of Ahmadkhani’s study. The results of Ahmadkhani's study indicate a positive correlation between wind speed, temperature, greenness and incidence of Brucellosis(21). The results of the present study are inconsistent with those of Tapak. According to the Tapak’s study, the wind at high speeds reduces the disease. This is because the bacterium has a shorter lifespan in the air.
The mean age of the patients was about 38 years. This result has been confirmed in other studies(22, 23). The results of this study indicate that P00 and P11 are larger than P10 and P01, respectively. In other words, states do not tend to change. That is, when we are in a non-outbreak state, the process tends to remain the same state. Also, P10 is higher than P01, which indicates that prolonged periods of non-outbreak lead to a reduction in the probability of outbreak during the year.
As the country's health progresses in many areas, the incidence of Brucellosis is expected to decline. However, the results of the present study indicate a sharp increase in the disease between 2014 and 2017, which requires a lot of health attention in Qazvin province. The necessary learning for high-risk age and occupational groups should be on the agenda of the region's health institutions. Not consuming unpasteurized dairy products and not having contact with suspicious animals and cooperating with livestock vaccination are among the preventive health behaviors to reduce the number of new cases of the disease.