A 32-year-old male labourer from rural Odisha presents to the primary health centre with fever for 3 days, chills, and myalgia. He reports working in rice paddies near a stagnant water body. On examination, temperature is 39.5°C, spleen is palpable 2 cm below the costal margin, and liver edge is felt 1 cm below the costal margin. Thick and thin blood smears show ring forms and trophozoites consistent with Plasmodium vivax. The patient has no previous history of malaria. Which of the following epidemiological features is MOST characteristic of his infection in this geographic and occupational setting?