May 25, 2018 -- Welcome to snake season. As the weather warms up, serpents will start to slither out of their winter hideouts and, inevitably, cross paths with humans. Such encounters may end in a trip to the emergency room.

“Throughout the spring and summer months, the numbers (of snakebite-related ER visits) double, triple, maybe even more than that,” says Diane Calello, MD, an associate professor of emergency medicine at Rutgers New Jersey Medical School in Newark. “It’s certainly a warm-weather phenomenon.”

The CDC estimates that as many as 8,000 people are bitten by venomous snakes in the U.S. each year. Such bites are rarely fatal. They kill about five people annually. But snake venom can cause serious harm.

“Venom causes pain and swelling and perhaps some blistering at the site of the bite, and it damages tissue,” says Bret Nicks, MD, a professor of emergency medicine at Wake Forest Baptist Health in Winston-Salem, NC. “Large amounts can cause internal bleeding.”

In the U.S., venomous snakes fall into one of two types: pit vipers and coral snakes.

Pit vipers share many physical traits, such as triangular heads, vertical pupils, and a pit between their nostrils and eyes. The snakes in this category include:

Rattlesnakes: There are many rattlesnake species throughout the U.S. “Among pit vipers, rattlesnake venom packs the most punch and causes the most problems,” says Calello, who's also executive and medical director of the New Jersey Poison Information and Education System.

Copperheads: These venomous snakes live mostly throughout the eastern U.S., but their habitat stretches as far west as Texas. “If you’re going to get bit by a venomous snake, this is the one you want because it doesn’t do a lot to you,” says Nicks.

Cottonmouths (aka water moccasins): Cottonmouth snakes can be found in the southeastern U.S. The like to be near water.

Coral snakes, says Nicks, live mostly in Florida and Georgia. They are black and red with white or yellow bands.