The Centers for Disease Control and Prevention on Thursday issued a health advisory over reports of a rise in invasive strep A infections in children.

While cases of strep A are currently relatively low and still rare in children, the CDC will continue investigating.

Group A Streptococcus is a category of bacteria that can cause illnesses ranging from pharyngitis to more dangerous diseases with high mortality rates like sepsis and streptococcal toxic shock syndrome.

In the U.S., strep A infections usually follow a seasonal pattern, with cases typically peaking in December through April. Cases also typically rise with high influenza activity, the CDC said.

The increase was first recorded in children at a Colorado hospital, with more states recordings cases since then, the agency said.

Last week, Colorados Department of Public Health and Environment said it had recorded 11 cases of invasive group A strep in children since Nov. 1 in the Denver metro area. Children ranging from 6 months to 10 years old make up most recent cases.

A possible reason behind the increase in infections could be the absence of mixing among children in the past few years due to the COVID-19 pandemic, according to health experts in the U.K. , where at least 15 children have died since September from a strep A outbreak.

CDC spokesperson Kate Grusich told CNN its not clear whether the number of infections is adjusting to pre-pandemic levels or rising beyond that.

The recent increases in respiratory viruses, particularly influenza, may also be contributing to a possible increase in iGAS infections, Grusich said.

The best way to guard against step A is practicing good hygiene, like frequently washing your hands, the CDC said.

There is no vaccine for group A strep, but keeping up to date on vaccines for COVID-19, flu and chickenpox can help protect your child from developing complications from a group A strep infection, said Dr. Rachel Herlihy, a state epidemiologist for Colorado.

Herlihy also urged parents to contact a doctor if they observe new symptoms.

Symptoms may include fever, chills and rashes, among other things.