Sepsis is an extreme inflammatory reaction to ongoing infection. It causes the immune system to attack tissues or organs in your body. Left untreated, you could go into septic shock, which may lead to organ failure and death.

Sepsis can occur if you don’t treat a bacterial, parasitic, or fungal infection.

People with a weakened immune system — children, older adults, and those with chronic medical conditions — are more at risk to contract sepsis.

Sepsis used to be called septicemia or blood poisoning.

Sepsis isn’t contagious. It may seem so because it’s caused by infection, which could be contagious.

Sepsis occurs most often when you have one of these infections:

There are also some germs that more often lead to sepsis than others:

Many strains of these bacteria have become drug-resistant, which may be why some believe sepsis is contagious. Leaving an infection untreated is often what causes sepsis.

How does sepsis spread?

Sepsis isn’t contagious and can’t be transmitted from person to person, including between children, after death or through sexual contact. However, sepsis does spread throughout the body via the bloodstream.

Sepsis symptoms at first may resemble a cold or the flu. These symptoms include:

If left untreated, these symptoms can worsen and cause you to go into septic shock. If you have an infection and you experience these symptoms, visit your doctor immediately or go to an emergency room.

According to the Centers for Disease Control and Prevention, more than 1.5 million people get sepsis annually in the United States. One in three people who die in a hospital have sepsis. Adults who have sepsis most frequently get it after experiencing a lung infection like pneumonia.

Although very dangerous, sepsis isn’t contagious. To protect yourself from sepsis, it’s important to treat infections as soon as they occur. Without treating infection, a simple cut can become deadly.