Infections caused by GAS can be mild to severe. Mild GAS infections include strep throat and minor skin infections such as impetigo. The CDC estimates more than 111 million children in developing countries get impetigo each year. When GAS bacteria get into or invade certain tissues of the body, more severe or life-threatening infections can occur. Erysipelas is a more severe form of skin infection. But it is often easily treated. Although rare, 2 severe invasive GAS infections are necrotizing fasciitis and streptococcal toxic shock syndrome. Necrotizing fasciitis is also known as “flesh-eating bacteria.”

GAS infections are spread through direct contact with saliva or nasal mucus. They also can be spread through direct contact with an infected skin wound. A person with strep throat is generally not considered contagious after taking an antibiotic for at least 24 hours.

GAS infections are rare in children younger than 3. GAS skin infections are most common in children ages 3 to 6. Strep throat is most common in children ages 5 to 15. Others at risk include people with a weakened immune system and adults with chronic skin conditions, diabetes, blood vessel disease, or cancer.

It's important to thoroughly wash hands for at least 20 seconds after coughing or sneezing. A person with a confirmed case of strep throat should stay home until 24 hours after starting an antibiotic.

GBS is the most common cause of life-threatening infections in newborns. These bacteria also can cause illness in pregnant women, elderly adults, and adults who have diabetes or liver disease.

About half of cases of GBS disease in newborns occur in the first week of life. Premature babies are more susceptible to GBS infection, but most of the cases of GBS occur in babies who are full term. Late-onset GBS disease occurs from 1 week to 3 months after birth, most often in the form of meningitis. In pregnant people, GBS can cause infections of the bladder and uterus, and stillbirth. Among people who are not pregnant, the most common diseases caused by GBS are blood infections, skin or soft tissue infections, diabetic foot infections, and pneumonia.

Other conditions that increase the risk include contracting GBS late in pregnancy; rupture of membranes 18 hours or more before delivery; and labor or rupture of membranes before 37 weeks.

The CDC recommends routine GBS screening for all pregnant people between their 35th and 37th week of pregnancy. If the screening shows GBS, the person is prescribed an antibiotic. If the person has had GBS at any time during the pregnancy, or is at high risk for it, they will usually be given antibiotics during labor.