In the United States, about 7,000 to 8,000 people per year receive venomous snake bites, including those of rattlesnakes, copperheads, cottonmouths and coral snakes, causing five to six average annual fatalities. Venomous snakes produce many different types of venom that help them obtain prey, digest prey and defend against enemies.
Different types of snake venom have distinctive toxic effects, depending on the species. For example, some species produce neurotoxins, which cause flaccid paralysis, some produce cardiotoxins, which affect the heart's function, and still others produce hemorrhagins, which damage the vascular wall of vessels, causing internal bleeding. However, venomous snakes have the ability to deliver specific amounts of venom when they bite, often delivering very small, non-toxic amounts of venom, or even no venom at all. This is known as a "dry bite." Snakes produce venom in a gland located just behind their eyes, with bigger snakes producing higher amounts of venom.
The most highly toxic species of snake found in the United States is the Eastern Diamondback Rattlesnake (Crotalus Adamanteus), according to toxicity studies performed on mice. Symptoms of a venomous snakebite include a pair of puncture wounds at the location of the bite, nausea and vomiting, labored breathing, increased sweating and salivation, blurry vision and numbness or tingling around the face and limbs.