"In 1799, when Tipu was defeated by the British, the whole of Mysore Kingdom with Srirangapatnam as Tipu’s capital, came under British control. For the next few days, the British soldiers had a great time celebrating their victory, but within weeks, many started feeling sick due to Malaria, because Srirangapatnam was a highly marshy area with severe mosquito trouble."

https://greatgameindia.com/the-history-of-hydroxychloroquine-in-india/