JQuery and any other similar technology, are awesome to use, so they are used so much actually, that it could possibly cause a danger in itself. I also see how many people now use a 3rd party connection to rely on to have their website function properly. I was never a big fan of that really. What if their server go down? That wouldn’t be the end of the world, or anything like that, but why rely on 3rd party connections, when the files are only text base, so small in memory size, and just host them yourselves?
The virus part, we cannot worry about too much… if it happens, it happens… but as far as relying on external connections to feed your page the technology it may need… I would consult that unless you have a really good reason not to do it, put them on your local server, and include them from there.