"Cockroach at the door." joke

A man was sitting at home one evening, when the doorbell rang.
When he answered the door, a 6 foot tall cockroach was standing there.
The cockroach immediately punched him between the eyes and scampered off.
The next evening, the man was sitting at home when the doorbell rang again.
When he answered the door, the cockroach was there again.
This time, it punched him, kicked him and karate chopped him before running away.
The third evening, the man was sitting at home when the doorbell rang.
When he answered the door, the cockroach was there yet again.
It leapt at him and stabbed him several times before running off.
The gravely injured man managed to crawl to the telephone and summoned an ambulance. He was rushed to intensive care, where they saved his life.
The next morning, the doctor was doing his rounds. He asked the man what happened, so the man explained about the 6 foot cockroach's attacks, culminating in the near fatal stabbing.
The doctor thought for a moment and said...
"Yes, there's a nasty bug going around."