Table 2.

Estimated relative risk of the presence of human cases of Eastern equine encephalitis as a function of the presence or absence of mosquitoes testing positive for the Eastern equine encephalitis virus, in the four counties of Madison, Oneida, Onondaga and Oswego, in Central New York State, 1971–2012^a

Species	Relative riskb,c	95% Confidence intervald	Proportion of human EEE when mosquito EEE virus present	Proportion of human EEE when mosquito EEE virus absent	Fisher's exact test, one-sided P-value
Aedes canadensis	14.67	1.86–115.49	0.444	0.030	0.005
Coquillettidia perturbans	6.38	1.27–32.05	0.375	0.059	0.03
Culiseta morsitans	5.50	1.08–28.08	0.333	0.061	0.05
Culiseta melanura	–	–	0.217	0.000	0.03
Culex pipiens-restuans	2.75	0.43–17.41	0.333	0.121	0.33
Aedes vexans	2.38	0.34–16.43	0.250	0.105	0.40
Anopheles quadrimaculatus	0.00	–	0.000	0.167	1.00
Anopheles punctipennis	0.00	–	0.000	0.185	1.00

^aUsing data in Table 1.

^bRelative risk is defined as the probability of a human EEE case occurring in a year in which the EEE virus was present for the listed species divided by the probability of a human EEE case occurring in a year in which the EEE virus was absent for the listed species.

^cRelative risk cannot be computed if the denominator is 0 (see Cs. melanura) and a confidence interval for relative risk cannot be computed if the proportion of human EEE when mosquito EEE virus present is 0.

^dConfidence intervals that include a relative risk of 1 would not be statistically significant (α = 0.05) which is the case for the last four species listed in the table.