microencephaly
Mosquitoes. That's right, mosquitoes. As creepy little transmitters of diseases such as the current Zika virus epidemic (linked with causing the birth defect microencephaly), West Nile virus, malaria, chikungunya, and dengue fever, mosquitoes kill over 1 million people every year according to the World Health Organization.
This fascinating video from PBS shows how they suck your blood:
I am using insect repellent this summer after watching that video!