Actually, the newest recommendations (posted on the CDC pages,) indicate similar effectiveness for DEET and lemon eucalyptus oil, and good effectiveness, though of lesser duration, for picaridin. Lemon eucalyptus oil and picaridin seem to avoid a couple of the problems DEET (N,N-diethyl-meta-toluamide,) especially in high percentage formulations (formulations in excess of 30% DEET are generally overkill,) can have, including that nasty "melting" effect on some synthetic clothing and plastic (such as some cameras,) though that could also be affected by the associated carriers, etc.

One problem I mentioned with dengue is Aedes mosquitoes are largely day biters - and due to the greater awareness of night-biting mosquito dangers (Anopheles species, transmittrs of malarial Plasmodia, are mostly night-biters,) some people don't protect enough during daylight hours. Nets and clothes that cover more are effective anytime they are used, and can be made even more effective by treating them with permethrin. Since permethrin treamtent persists even through a few launderings, it is cost-effective and can be applied to clothing and nets before leaving home.

West Nile indeed - in the Sacramento area, it appears we lost a majority of our corvid numbers last year (crows, scrub jays, yellow-billed magpies,) as corvids have little resistance to WNV.