"Preston told CBS News that months after leaving the jungle, he noticed a bug bite that simply wouldn’t go away. And so did half his team members. Eventually, the National Institutes of Health diagnosed them with Leishmaniasis — a rare parasitic disease — and the team was forced to undergo treatment"
So I looked at wikipedia, and the article [1] there says:
"About 12 million people are currently infected in some 98 countries. About 2 million new cases and between 20 and 50 thousand deaths occur each year. About 200 million people in Asia, Africa, South and Central America, and southern Europe live in areas where the disease is common."
Not unusual indeed.
> Leishmaniasis is mostly a disease of the developing world, and is rarely known in the developed world outside a small number of cases
So, not rare for where they visited, but rare for where they live (and where the diagnosis happened).