Table 2.

Multivariable analyses showing sociodemographic and environmental factors associated with chikungunya cases in the census sectors of Salvador, Brazil.

Census tracts characteristics	2019–2020a	2019	2020b
	Incidence risk ratio (95% confidence interval)
Head of household mean Income (per thousands of reaisc)	0.86 (0.83–0.90)	0.89 (0.84–0.94)	0.87 (0.83–0.91)
Density (Inhabitants per 100 m2)	0.78 (0.77–0.80)	0.80 (0.77–0.83)	0.78 (0.76–0.80)
Land Surface Temperature (per 1 °C)	1.18 (1.12–1.25)	1.22 (1.12–1.33)	1.15 (1.08–1.22)
Soil Adjusted Vegetation Index (per unit increase)	0.45 (0.22–0.92)	1.07 (0.34–3.41)	0.36 (0.17–0.77)
Altitude (per 100 m)	1.19 (0.90–1.57)	0.91 (0.59–1.39)	1.35 (1.00–1.82)
Chikungunya incidence in 2019
<500 cases per 100,000 pop.	–	–	1.00
500–2999 cases per 100,000 pop.	–	–	1.63 (1.42–1.88)
3000–4499 cases per 100,000 pop.	–	–	7.89 (4.60–13.54)
≥4500 cases per 100,000 pop.	–	–	1.20 (0.51–2.86)

Note: Values with statistical significance are in bold. Statistical significance was determined when the 95% confidence interval did not enclose the value reflecting no effect (incidence risk ratio of 1).

^aCumulative incidence between 2019 and 2020.

^bIn the case of the 2020 model, the 2019 incidence was included, categorized into four categories.

^cThe average dollar exchange rate for 2010 (at the time of the census) was 1 real = 0.57 US dollars.