Mild GAS infections include strep throat and minor skin infections such as impetigo. Invasive GAS infections include toxic shock syndrome and necrotizing fasciitis. These invasive infections, although life threatening, are rare.

GAS infections are spread through direct contact with saliva or nasal discharge. Consuming contaminated milk and milk products also may also transmit the infection, according to the NIAID. Contamination of pasteurized milk is rare but the infection could be passed on through raw milk. A person who contracts a GAS infection usually becomes sick within three days of infection. A person with a GAS infection can pass on the bacteria for up to three weeks afterward.

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 weakened immune systems; and elderly adults with cellulitis, diabetes, blood vessel disease or cancer.

It's important to thoroughly wash hands after coughing or sneezing. A person with a confirmed case of strep throat should stay home until 24 hours after starting an antibiotic, the NIAID says.

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

Three-fourths of cases of GBS disease in newborns occur in the first week of life, the NIAID says. Although premature infants are more susceptible to GBS infection, most of the cases of GBS occur in babies who are full term. Late-onset GBS disease, a rare form of GBS, occurs several months after birth, most often in the form of meningitis. In pregnant women, GBS can cause infections of the bladder and uterus, and stillbirth. Among men and among women who are not pregnant, the most common diseases caused by GBS are blood infections, skin or soft tissue infections, and pneumonia.

According to the NIAID, 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.

This applies to a woman who has had a previous child with GBS disease or a woman who has a urinary tract infection caused by GBS.