Cases of invasive group A strep infections, which can cause severe illness and be deadly, remain elevated in some parts of the country, officials warned Wednesday.
In a statement to ABC News, the Centers for Disease Control and Prevention confirmed that "preliminary" data from 2023 suggests cases have remained elevated above pre-pandemic levels in some areas of the U.S.
This follows confirmed reports that five children have died of invasive Strep A so far this year in Illinois.
WATCH: Illinois' top doctor warns of strep throat in children after 5 pediatric deaths reported
After a lull of invasive Strep A cases during the COVID-19 pandemic, recently, cases of invasive Strep A have been ticking up again. The CDC warned in December that cases of Invasive Strep A were on the rise. The WHO first reported a surge of GAS infections across several countries that same month. Data from the U.K. revealed that in late 2022, there was nearly triple the number of Group A Strep infections than the same period over the last five years.
The CDC told ABC News Wednesday that the number of invasive strep A illnesses in children in the U.S. have returned to -- and in some places exceeded -- levels seen prior to the pandemic.
In December, the CDC warned that cases of Invasive Strep A were on the rise. A subsequent CDC analysis suggested a roughly threefold increase of cases in Colorado and Minnesota during October through December 2022, as compared to pre-pandemic years.
"Preliminary 2023 data indicate that [invasive Strep A] infections have remained high in children in some areas of the country even after some respiratory viruses decreased in those areas," the CDC said in a statement. "Some areas of the country are seeing higher levels than were seen pre-COVID-19 pandemic."
The typical Strep A season runs from December through April, according to the CDC.
Here are five questions answered about the condition, from how to treat it to how to lessen the risk.
1. What causes invasive group A strep?
Group A Strep (GAS) is a common bacteria which lives on our skin and often in our throats. It can cause different types of infections, most often strep throat.
Rarely, it can cause severe infections like streptococcal toxic shock syndrome or necrotizing fasciitis, a rare bacterial infection.
The severe infections occur when strep A bacteria invades other parts of the body like the bloodstream or spinal fluid.
2. How common is invasive group A strep?
Invasive group A strep is a dangerous but rare disease that leads to around 1,500 to 2,300 deaths in the United States annually, according to the CDC.
The agency says between 14,000 and 25,000 cases usually occur each year.
Cases of invasive group A strep are more common among children.
3. How is invasive group A strep treated?
The condition is usually treated in the hospital with IV antibiotics and other supportive measures.
The treatment for mild to moderate strep infections is amoxicillin, which is on national shortage. If strep goes untreated or undertreated, it can lead to invasive group A strep.
At this stage, there is no data to suggest a direct link between the shortage of amoxicillin and the spike in cases.
4. What are the most common symptoms of invasive group A strep?
Doctors tell ABC News that all cases of strep should be seen by a doctor, severe or not.
Parents and caregivers should be on the lookout for fever, sore throat, trouble swallowing, or kids not acting like themselves.
Parents should also keep an eye out for signs of toxic shock syndrome and "flesh-eating" skin infections, which can be a sign that a strep infection is invasive. Symptoms of toxic shock include fever, chills, muscle aches, nausea and vomiting, according to the CDC.
Early signs of a serious skin infection include a fast-spreading swollen area of skin, severe pain and fever. Later on it might look like blisters, changes in skin color or pus at the infected area.
5. How can a person lessen their exposure to invasive group A strep?
Because strep spreads through coughs and sneezes and surfaces, practicing good hygiene -- like washing hands, surfaces and plates or glasses -- can keep it from spreading.
Viral infections can set the stage for a subsequent bacterial infection in the lungs, so parents and caregivers should also make sure children are up to date on flu and COVID-19 vaccinations in order to help protect them.