Answer
Malaria is a mosquito-borne disease that causes symptoms such as fever, chills, and muscle aches. In 1868, Chulalongkorn and his father contracted malaria while visiting Europe. Chulalongkorn was hospitalized for a month, but his father died from the disease. This experience made Chulalongkorn aware of the need to improve the health of his people and led to his establishment of a modern public health system in Thailand.