All this costs us all a lot of money and adds harmful chemicals to our air. After all, a mature bat eats around 5000 flying insects per night. For free! You can learn more at www.BatWorld.org - the website for an excellent, non-profit bat rescue place here in north Texas.
You're totally right to be concerned about any disease carried by birds, no matter how rare or improbable the diseases are. True - cold weather slows or stops the trasnsmission of many bird diseases. But not all! Make sure the birds that visit your yard are healthy enough to fight off diseases, and can have the energy it takes to stay warm. Even now, clean your feeders with a mixture of 90% water and 10% bleach or vinegar.