The likelihood that a spider will bite a human is very low. Spiders avoid humans and do not feed on human blood, and most are physically incapable of biting through human skin.
The majority of presumed spider bites actually are the bites of other insects, such as fleas. When spider bites actually occur, it is usually because the spider is startled.
Of the more than 40,000 species of spiders, only about a dozen worldwide are venomous to a healthy human adult. Of these, only the widows and recluses are found in the United States.
Additionally, even if a human is bitten by a spider, the risk of death is small. In the United States, about 6.5 people die annually from venomous spider bites. According to the Centers for Disease Control and Prevention, 70 people in the United States died from venomous spiders between 1999 and 2007.