Back wen Katrina happened in Louisiana, then Mayor, Ray Nagin said that he didn't know what they'd do once the mosquitoes started biting dead bodies. I LOLed so hard at the thought of him worrying about zombies. I get what he really meant, but it's still funny.
And the mosquito thing is a problem in Resident Evil/Dead Rising type zombies(virus/plague), but Walking Dead and Romero Zombies(divine judgement/unknown) shouldn't matter.
But people fighting zombies(story wise) have to be able to get at least a little zombie blood on them, so a mosquito's amount of it might not be enough to transmit when it bites them.
RL viruses work, but the fake zombie virus in some stories might not transmit it. Rage virus probably works.
I've always wondered what their explanation for it is. :{