You should recognize the families and structures of the commonly occurring and medically relevant viruses. Proper names are probably not as important, but knowing them may help you remember the family groupings. There were questions on my exam about which viruses were RNA/DNA/naked/enveloped/etc - as with many boards questions, sometimes the answer was a 2nd or 3rd step in the thought process. So, you might have to know the symptoms of a common viral infection, then know which virus caused it, but the actual question is, is it an RNA or DNA virus, does it have a segmented genome, etc.
This is of course a relatively small part of the exam, but it's similar in scope to many of the other details that are tested. You shouldn't be surprised that this level of understanding would be expected.