Elephants are contagious!
Be careful how you tread.
An Elephant that's been trodden on
Should be confined to bed!

Leopards are contagious too.
Be careful tiny tots.
They don't give you a temperature
But lots and lots - of spots.

The Herring is a lucky fish
From all disease inured.
Should he be ill when caught at sea;
Immediately - he's cured!

Spike Milligan

http://www.poemhunter.com/poem/contagion/