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!