In the Denver metro area alone, there have been 11 reported cases of invasive group A strep (sometimes shortened to iGAS) in children between 10 months and 6 years old, according to a press release from the Colorado Department of Public Health and Environment. Although these infections are still rare, the Center for Disease Control and Prevention (CDC) is currently investigating a possible increase. What is invasive group A strep and what symptoms signal a dangerous infection? Here’s what you need to know to keep your family safe.

What Is Group A Strep?

“Group A streptococcus is a bacteria; it’s notorious for causing sore throat,” says William Schaffner, MD, who serves as a professor of medicine in the division of infectious diseases at Vanderbilt University Medical Center in Nashville, Tennessee. Group A strep circulates all the time and many of us are harmlessly colonized with it in our throat, says Amesh A. Adalja MD, a senior scholar at the Johns Hopkins Center for Health Security in Baltimore. The bacteria called group A strep can cause many different infections: Some are minor illnesses, but in other cases, the diseases can cause severe illness and even death, according to the CDC.

What Is Invasive Group A Strep?

“Invasive group A strep infections happen when the bacteria gets past the initial defenses of the person who is infected with strep group A,” says Dr. Schaffner. In this more severe infection, the bacteria gains access to deeper sites in the body, versus just the skin or throat, for example, says Dr. Adalja. “Examples of iGAS disease range from pneumonia, to abscesses, to necrotizing fasciitis [a life-threatening skin infection caused by ‘flesh-eating’ bacteria], to bloodstream infections and to toxic shock syndrome, in which multiple organs systems are malfunctioning due to infection,” he says.

What’s Causing the Rise of Invasive Group A Strep?

Because group A strep is always around, the question isn’t why it’s circulating, but rather why invasive group A strep appears to have increased above expected levels, says Adalja. It’s likely that what is happening in Europe is a worldwide phenomenon, similar to what we’re seeing with the “tripledemic” spike in RSV, COVID, and flu, he says. Schaffner similarly believes that the rise in iGAS is likely due to the spread of the flu. For the week ending December 10, seasonal flu activity remains high, per the CDC. Invasive group A strep infections can occur as a complication of respiratory viruses such as the flu, says Schaffner. “Influenza attaches itself to cells in the mucous membranes of the nose, the throat, and down in the bronchial tubes. That causes inflammation and kind of ‘roughs up’ that mucous membrane,” he says. If we happen to be carrying group A strep in our throats when we get these influenza infections, the strep bacteria may be able to penetrate the mucous membranes and infiltrate the bloodstream, says Schaffner. There may also be a heightened susceptibility to iGAS because of the lack of exposure experienced during the height of COVID-19, due to social distancing and masking recommendations, adds Adalja. “As we are now out and about and in general, taking few precautions, we’re providing group A strep much more opportunity to spread amongst ourselves along with viruses we’ve been hearing about: influenza, RSV, and COVID,” Schaffer says.

Very Young Children and the Elderly Are at the Highest Risk for Infectious Group A Strep

Few people who come into contact with group A strep will develop infectious group A strep. The CDC estimates that most years, about 14,000 to 25,000 cases of iGAS occur in the United States, resulting in between 1,500 and 2,300 deaths. Anyone can become infected by group A step, but people who have sores or breaks in the skin that allow the bacteria to enter the tissue are at higher risk. Health conditions that decrease immunity also make iGAS more likely. There are certain types of iGAS that are more likely to cause severe disease, and it’s more likely to be fatal in the very old and very young, says Adalja.

Signs and Symptoms of Group A Strep Infection

Group A strep most commonly causes sore throat, according to the CDC. Strep throat is very contagious, and it’s spread through respiratory droplets, direct contact, and in rare cases, food that’s not handled properly, per the agency. It usually takes between two and five days for someone who is exposed to group A strep bacteria to get sick with strep throat. Symptoms include a sore throat that comes on very quickly, fever, swollen tonsils, swollen lymph nodes, and a red, rough rash or strawberry tongue. (Strep throat with a rash is called scarlet fever, per the CDC).

Strep Throat Needs to Be Diagnosed by a Healthcare Professional

The only way to know if a sore throat is caused by a bacterial strep infection (rather than a virus like COVID-19 or the flu) is by going to the doctor, says Adalja. A doctor’s office can administer a rapid strep test and deliver results in just a few minutes. However, the test sometimes comes back negative even when strep is present, and so the doctor might order a throat swab or culture for laboratory analysis. This kind of testing is more reliable than the rapid strep test but results can take a day or two. If the strep test comes back positive, doctors may prescribe a course of antibiotics, according to the CDC. Penicillin or amoxicillin is the antibiotic of choice, unless the patient has an allergy. It’s important to take these antibiotics in the way the doctor prescribes and for the appropriate number of days, even if symptoms disappear (usually about one to three days after beginning medication).

Seek Medical Care if the Sick Person Becomes Lethargic or Stops Eating or Drinking

According to the CDC, the potential rise of iGAS in children means that parents should be aware of the symptoms for necrotizing fasciitis and streptococcal toxic shock syndrome. Seek medical care right away if you suspect your child has one of these conditions. If a child or adult becomes lethargic, isn’t eating or taking in fluids, or looks sick, they should seek care immediately, says Schaffner. “We do have good antibiotics that can fight off these strep infections, along with good supportive care, and the sooner you start treatment, the better,” he says.

How to Reduce the Risk of Invasive Group A Strep

Early treatment of strep throat is critical to keeping initial group A strep infection mild, and is the best way to prevent a serious illness caused by iGAS, per the Colorado Health Department. In addition to getting prompt treatment for strep throat, there are a few other ways to reduce the risk of invasive group A strep. Number one: Practice good hygiene, including frequent hand-washing or using hand sanitizer when you can’t wash your hands, per the CDC. Make sure children are up to date with flu and chickenpox vaccines, since getting these infections can increase risk for getting iGAS, according to the CDC. Getting the latest bivalent COVID-19 booster is a good idea, too, says Schaffner.