Table 3. Risk factors associated with anti-dengue immunoglobulin M (IgM) seropositivity in Nuevo Laredo/Laredo residents, by univariate analysis.

Risk factor	Prevalence ratio	Mean value for IgM seropositive residents	Mean value for IgM seronegative residents	(95% confidence interval) or p value
No air-conditioning	2.6	—	—	(1.3 to 5.2)
Evaporative cooler	2	—	—	(1.2 to 3.3)
No travel beyond Laredo/Nuevo Laredo area	1.9	—	—	(1.0 to 3.5)
No. room air conditioners	—	0.3	0.6	p=0.05
Distance to neighbor (m)	—	2.4	3.8	p=0.003