It means that the bacteria is able come in contact to your skin. Transport link to your arm kind of means that it is jumping from somewhere to your arm or skin. Try to think transport link as a bridge!

Actually now that I look at this again, what they mean is to arm the bug with a virus. Like arming a solder with a gun..the solder is now armed! So they are saying, that a harmless bacteria can pass on a deadly bacteria. The transport link is like a train station where you connect with places.