Associate
I'd lean towards it being from disease especially if you didn't stick to bottled water - various colleagues have visited that part of the world over the years and either them or one or more of their family have inevitably ended up with something due to water/food or ended up with dengue fever or the likes.
Interestingly, thanks to global warming, the Tiger mosquitoes that carry Dengue fever have recently been found in Kent. Dengue outbreaks have been rising in Europe in recent years, with eight incidents of multiple infections reported in France, two in Italy and two in Spain.