Antivirus on intranet network

[Steven Meyer <meysteven () gmail com>]

hello,
I have a "Working" network who is totally disconnected (physically)
from the Internet.
people do the "search" on the "Internet " computers and then go on the
"work" computers for analyse and the store the data.
The Question is: I would need a anti virus on the "work" computers and
I should be able to update the virus database daily without connecting
any computer to the Internet.
Which anti virus should I use and How could I do the update.
Thanks for any help.
Steven Meyer