There are a couple of reasons to use AV software in Linux. One is to
protect yourself just in case and the other is to protect others. You can
pass on viruses even if you can't become infected.

That being said, I do not use any AV protection. Linux AV programmes do not
work as well as Windows ones and are difficult to set up. Scanning email
attachments and downloads in the background as in Windows is hard to
achieve. You usually have to do this manually and it becomes more of a pain
than anything. After trying it you will find that it just is not worth the
trouble due to the remote possibility of infection.

Unless you are paranoid about security then you probably will not go to all
of that hassle. The reasons why Linux AV software is not as good is that
there is little need or demand and part of the reason for that is that
security is built into Linux. This is partly why it is hard to set up
scanning automatically. You need to give permission for anything remotely
risky, even AV scanning, since you will likely be scanning the boot sector
and the kernel.

K/Ubuntu has done away with much of this risk by not allowing root login.
Some distros allow you to do this and Windows users may be tempted because
it makes life easier to only input a password at login or not at all. That
is not the way Linux is meant to work and it is why Linux beats the pants
off Windows and OS X every year in an annual hacking contest. Linux security
when properly followed is good.

Many people speculate that Linux is not targeted because it has so few users
and that Widnows is targeted because it is so many. However, the challenge
of infecting Linux should be great enough to encourage virus developers.
Windows should be no contest for them. When Ubisoft said its DRM was hacker
proof, hackers broke it in a day. The challenge is out there. Linux has much
of the server market so maximum damage to big companies could be done if it
was possible.

The big difference I think is that Linux users are sufficiently wise that
viruses would not propagate. In other words, careless people get infected in
any OS and Windows encourages users to be careless. Linux encourages people
to take security seriously and therefore while some individuals may get
infected it isn't likely to spread far. Windows has tried to close security
holes, but Microsoft is so slow at it that a virus can make serious damage
before the react. In contrast, Linux is a collaborative effort and fixes are
often out the same day that they are discovered. Also most users update
often enough and are better informed about security threats that they
install updates right away. The thing that can hurt Linux the most is
Windows users who move over and bring bad Windows habits with them. That is
why I accepted sudo and no root login as the better method in the end. It
removes temptation.

As long as you follow established protocols I think that you are reasonably
safe and that if a threat surfaces it would travel so slowly that you would
have advance warning and can take further steps. However, there are Linux
versions of many popular AV applications such as Bitdefender and AVG. Use
them if you want. Chances are that the novelty will wear off.