How do the mosquitoes become infected with eastern equine encephalitis (EEE) virus?

How do the mosquitoes become infected with eastern equine encephalitis (EEE) virus?

Certain types of mosquitoes become infected by feeding on birds infected with eastern equine encephalitis (EEE) virus. These mosquitoes then bite humans and animals. The birds themselves originally became infected by being bit by yet a different species of mosquito.