It makes me think of the charts they use to track malaria and undulant fever.
(
like this)
That's actually how undulant fever got its name - the undulations on the chart depicted the rising and falling of the fever.
This always causes a weird short circuit in my brain, though, since undulant fever is also brucellosis, which is a disease of cattle and buffalo, which are ungulates. I can never decide if I should be saying
Undulant Fever or
Ungulate Fever.