I wouldn’t be too quick to dismiss Little Ed. A quick Google search on “cholera belt” turned up references to the geographic region (as well as enough information to enlighten our Mensa friend). To excerpt from a document regarding cholera in Luanda, Angola:
http://sae.amm.uniroma1.it/cirps/Angola/pubd.htm
“In April 1987, a new outbreak started in the northeastern part of the country, an area of the epidemic cholera belt of Austral Africa which also includes Zambia, Malawi and Mozambique.”
The column in question being: What’s a cholera belt? (Cecil likes it when you include a link to the referenced column).
From the information I’ve been able to find on this, it looks like the use of “Cholera belt” to refer to an article of clothing came before using it as a geographical marker.
There is a Manx/Gaelic word, cryss chollyr, that translates as “cholera belt,” in the clothing sense of the word. It originated at the time that British soldiers were being sent over to India (apparently a fair amount of the flannel and knitting for these belts came from areas that spoke Manx). This definitely predates any usage of “Cholera Belt” to refer to any part of Africa.
Also, there seems to be a disagreement over what region actually is the Cholera Belt. I’ve seen people refer to areas around Pakistan and India as the belt. Though it does seem (from a quick search of online medical documents) that most cholera cases these days are coming from Africa.