Several epidemics throughout history have many similarities in characteristics. For example, many diseases evolved from poor hygiene between animals and humans and a rise in urban population and interregional communication. Many had very similar effects and modes of transmission.
Because of the similarities, many historians are looking into allegations of these diseases stealing each other's methods, committing plague-iarism.
Shopping for Underwear
A man walks up to the counter. "Two pairs of underwear please." The man behind the counter looks at him in disbelief.
"Only two pairs of underwear?"
"Yup. I wear one while the other is in the wash."
The man behind the counter looks at him in disgust, then rings out his order.
A second man walks in. "5 pairs of underwear please."
"Only 5 eh?"
"Yeah, I wear one for every weekday, then go commando all the weekend."
The man behind the counter shakes his head. "Well, you're better then the last guy!"
A third man walks in. "7 pairs of underwear please."
"Finally, a man who knows hygiene!"
"Yes, I do try. One for every day, and I do my laundry on Sunday."
At the end of the day, a fourth man walks into the underwear store. "12 pairs of underwear please."
"Wow! You must be really clean!"
The man smiles. "Yup, that's me! Err, hang on, let me see if I counted right. January, February, March, April..."