There’s an old Japanese saying that’s rather apt for this time of year: “Bunbō gyūyō o hashirasu,” which roughly translates to “mosquitoes and horseflies can make cattle run.” The implication is that even the weak can move the mighty, or the trivial can cause disaster.

Mosquitoes aren’t a rare sight — or bite — in Japan, and they’re as much a part of a Japanese summer as cicadas or cockroaches. However, these tiny little bloodsuckers are more than just annoyances: Zika virus, dengue fever, malaria — mosquitoes are capable of spreading an assortment of infectious diseases to humans, sometimes with horrific consequences. In fact, these tiny flies cause more human suffering than any other creature on the planet, helping to kill over a million people worldwide each year.

While Japan has largely succeeded in containing major epidemics from diseases spread by mosquitoes through the use of vaccines and careful border inspections, the country is by no means immune. In 2014, Japan recorded its first dengue outbreak in 70 years, while a few cases of Japanese encephalitis are reported every year.