Recently a resurgence of West Nile Virus has been found in Palm Beach County in flocks of chickens monitored for this problem (and reported in the Palm Beach Post). Warm, humid weather has probably increased our mosquito population.
Species of parrots that are commonly kept as pets can be susceptible to infection and disease, although not as susceptible as other species (i.e. the risk is fairly low). There is a vaccine for horses but it doesn’t have good effectiveness to protect our birds, unfortunately (frequent revaccination necessary for example).
The best way to keep your birds safe is to do your best to keep mosquitoes away from them. Make sure there is very good screening of windows and doors (and close screen doors as quickly as you can entering and exiting), and keep birds indoors during times of the day with active mosquitoes (tending towards dusk and dawn). Control standing water in you yard. There are mosquito controls available as well (disks that go into small pools or fountains).
If your birds stay outside do your best to use mosquito netting around your bird’s aviary. If not possible, since these birds may be at higher risk, it might be worth to consider vaccination even with poor effectiveness of the vaccine.
Parrot species can show only mild non-specific signs which resolve spontaneously, or they can show significant neurologic signs, and the disease can potentially be fatal.