I ran across this new type of illness while reading a diary from 1862. I don't know if you're like me but this was a new term to me.
The illness is called Dengue Fever and it occurs in tropical and sub-tropical regions. We don't see a lot of it today, if any, because of our medical knowledge and treatment of limiting the mosquito population.
Here a link to read about this disease:
And from Wikipedia
The knowledge of the disease spreading by way of mosquitos was not known in 1862, the assumption was that the illness was an air born disease.