No, you are not correct. The number of viruses affecting the Mac is, in fact, zero. Each of the articles to which you linked incorrectly identified trojan horses as viruses. There is an enormous difference between the two.
Viruses are typically much more dangerous because they can move between computers and start running without the user doing anything. Trojan horses generally rely on trickery to fool computer users into installing bad things on their computers.
In the recent trojan horse case, victims would see a message telling them that they had a virus on their Macs. The message would offer a link to download a virus protection program in order to get rid of the problem. Most people were wise enough to ignore the fake message but some people fell for it and clicked the link to download and run the program. Once the program started running, the victims then entered their administrator password when prompted which gave the bad program access to the entire computer. Some people even entered their credit card information to "purchase" the program.
Unfortunately, there is very little any operating system can do to protect people from trojan horses. About the only way to do it is to prevent people from installing any program on their computers, which is not going to happen.
