Cuban experiences an annual endemic-epidemic of leptospirosis, a bacterial infection brought on usually through poor sanitation after natural disasters, such as hurricanes and flooding experienced in the area.

A homoeopathic remedy (specifically a homeoprophylaxis) was used and endorsed by the Finlay Institute, which is part of the Ministry of Public Health in Cuba.  They administered repeat doses to an estimated 2.5 million people at a cost of $200,000 (as opposed to the usual pharmaceutical drug cost of $3M).

Here is the article.