Birds dispersed the ticks over average distances of 260 to 3,100 miles.
Climate change will have increasing effects on public health and food security over time, the authors say.
The finding has important implications amid the heavier floods, more extreme droughts, and greater seasonal precipitation tied to climate change.
Multiple factors are fueling rises and compounding the impact, including shifts in dengue serotypes.
Catastrophic flooding in Pakistan last year led to a fivefold jump in cases.
The groups issued a call to action, including steps like including maternal and child health in climate and disaster plans.
The annual Lancet report details the health impacts of climate change, such as Bangladesh's record dengue outbreak.
The investigators found that summer temperatures accounted for 16% and 22% of overall fatal hospitalizations for respiratory diseases in Madrid and Barcelona, respectively.
Longer transmission seasons and migration of mosquitoes to new latitudes threaten to undo years of progress.
Several of the El Nino health risks are due to water contamination, either from flooding or drought. Malnutrition due to food insecurity was the top threat.