After El Niño events, malaria risk has been observed to increase by what magnitude?

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When malaria risk is linked to El Niño, the main idea is how climate variability drives mosquito biology and transmission. El Niño often shifts rainfall and temperatures in malaria-prone regions. In the years after an El Niño, many areas experience more favorable conditions for Anopheles mosquitoes—more standing water to breed and warmer temperatures that speed up parasite development inside the mosquito. Those combined effects can substantially boost transmission, commonly described as about a fivefold increase over baseline levels. So the observed pattern is a significant rise in malaria risk in the years following El Niño, not a decrease or no change. The option about affecting only non-human hosts doesn’t fit malaria transmission, which involves humans as the recipients of infection.