(NEXSTAR) — As flu and RSV move across the U.S. and elsewhere – in addition to COVID-19 – there are increasing concerns about strep throat, and the bacteria that causes it, streptococcus. Like RSV, or respiratory syncytial virus, strep is especially of concern for younger people.

Going into winter 2022, the Centers for Disease Control and Prevention says it’s looking into a possible surge in invasive Group A strep infections in the U.S.

Two children died from group A strep in the Denver area since Nov. 1, according to the Colorado Department of Public Health and Environment. Meanwhile, the United Kingdom has reported that at least 19 children have died from Strep A infection since Sept. 1.

While researching “strep throat” or “Group A strep,” you may also come across information on Group B strep, or even types C, D, F, G and H.

Groups A and B are the two groups most commonly associated with infections in humans. There are many key differences between Group A and B strep, as outlined by the CDC.

Group A strep (GAS)

What it can cause: Strep throat, scarlet fever, cellulitis, rheumatic fever, impetigo, streptococcal toxic shock syndrome, necrotizing fascitis, and post-streptococcal glomerulonephritis. These diseases and/or infections are often referred to as “invasive Group A strep infections,” or (iGAS).

Who’s most at risk: In general, school-aged children and adults who are in contact with them. Adults with other medical conditions, in addition to the elderly, are also at increased risk.

How it spreads: Respiratory droplets, direct contact with an infected person.

Group B strep (GBS)

What it can cause: Meningitis, bacterial pneumonia, urinary tract infections, sepsis. Group B strep can also cause infections of the blood (bacteremia), bone/joints and skin and soft tissues.

Who’s most at risk: Newborns and adults with medical conditions like diabetes, cancer and heart disease.

How it spreads: Group B strep is naturally found in some people’s intestines and genital tracts. Pregnant mothers can pass it on to newborns. The CDC says while it’s “generally unknown” how people spread GBS, you’re not at increased risk of getting sick by living with or being around people who do have it.

Treatment

For both types of strep, the CDC says antibiotics will usually be prescribed by a doctor. For certain conditions, like bone or soft tissue infections, surgery may be needed.

In October, Dr. Matthew Weissman of Mount Sinai Beth Israel hospital in Manhattan, told PIX11 Morning News that getting antibiotic treatment for strep is essential.

“The big problem with strep is that risk that if it’s untreated it can lead to other medical conditions, in particular rheumatic fever, which can cause all kinds of problems with your bones and joints and, most importantly, with your heart and heart valves,” he said. “So really important, if it is strep, to get antibiotics and to finish the full course of the antibiotics.”