Our reporter, Apoorva Mandavilli, goes inside a mosquito factory in Brazil, where scientists are producing millions of mosquitoes to fight deadly tropical diseases in a warming world.

The city of Belém in northern Brazil was overwhelmed by an outbreak of dengue two years ago. An all-out municipal effort has reduced cases and may offer lessons to American cities.

No medications were affected, but if new prevention items are not procured, aid groups fear a surge in new infections next year.