When we first came here this trip the kids had fevers,colds etc etc..I even had to take them to the hospital to get them checked out for Dengue et all..
I put it down to the vast climate change..For some people it takes time to adjust.
No way did you have Dengue or Malaria IMO.. (Malaria is pretty rare here)
Take mossy spray with you (containing DEET) and use it before dusk EVERY evening.
Supermarket spring water is good if you are only there for a week or two..
We have a trusted water purified outlet that we use and buy 50 Gallons at a time for home consumption.