Table 2 Univariate negative binomial regression (NBR) models for the DF incidence rates by month with incidence rate ratio (IRR) and 95% confidence interval (CI)

January

2.73 (1.19-6.26)*

1.26 (0.73-2.18)

1.61 (1.03-2.53)*

2.12 (1.39-3.22)*†

February

Reference: 1

Reference: 1

Reference: 1

Reference: 1

March

1.36 (0.59-3.14)

0.90 (0.52-1.56)

0.84 (0.54-1.32)

1.04 (0.68-1.59)

April

1.43 (0.62-3.30)

1.12 (0.65-1.92)

0.71 (0.45-1.11)

1.69 (1.11-2.56)*

May

5.14 (2.24-11.77)*†

1.34 (0.78-2.30)*

0.71 (0.45-0.11)

2.58 (1.70-3.92)*†

June

6.63 (2.90-15.19)*†

1.79 (1.04-3.09)*

0.99 (0.63-1.54)

3.28 (2.16-4.98)*†

July

14.94 (6.52-34.17)*†

2.55 (1.43-4.39)*†

1.40 (0.89-2.19)

3.58 (2.36-5.45)*†

August

22.02 (9.63-50.34)*†

2.46 (1.43-4.24)*†

2.06 (1.31-3.22)*†

4.57 (3.01-6.94)*†

September

38.47 (16.83-87.94)*†

2.35 (1.36-4.04)*†

1.91 (1.22-2.99)*

5.26 (3.46-8.00)*†

October

55.07 (23.65-123.59)*†

2.69 (1.56-4.63)*†

2.40 (1.53-3.76)*†

4.49 (2.95-6.83)*†

November

46.69 (20.43-106.73)*†

2.22 (1.29-3.83)*†

2.35 (1.50-3.67)*†

3.49 (2.30-5.31)*†

December

13.44 (5.88-30.74)*†

1.75 (1.02-3.01)*

1.84 (1.18-2.89)*†

3.01 (1.98-4.58)*†