(CNN) The US Centers for Disease Control and Prevention says it's investigating an apparent increase in invasive group A strep infections, but the rise may indicate a return to typical pre-pandemic levels.
Much like flu and RSV, invasive group A strep infections, known as iGAS infections, were curbed by Covid-19 control measures such as masking and social distancing. But in a statement Friday, the CDC said it's now hearing from some doctors and state health departments about an increase in iGAS infections among children.
"It's too soon to say whether iGAS case numbers are just returning to pre-pandemic levels or if they are rising beyond what we would normally expect based on what we know about GAS seasonal patterns," CDC spokesperson Kate Grusich wrote In an email.
"The recent increases in respiratory viruses, particularly influenza, may also be contributing to a possible increase in iGAS infections. Concurrent or preceding viral infections such as influenza and skin conditions such as chickenpox may increase risk for iGAS infections."
The Colorado Department of Public Health and Environment said Friday that it is monitoring an increase in pediatric hospitalizations caused by group A strep. The rise follows a drop in cases during the pandemic.
"Cases of invasive group A strep have been increasing in all age groups, but is especially apparent this fall in pediatric patients," spokesperson Paul Galloway wrote in an email.
There have been 11 reported cases of invasive group A strep in children 10 months to 6 years of age in the Denver metro area since November 1, the department said. Two children have died, but the official cause of death has not been determined, Galloway said.
This month, health officials in the UK advised parents and schools to monitor for strep A infections after the deaths of several children.
The World Health Organization said Thursday that France, Ireland, the Netherlands, Sweden and the UK have reported an increase in iGAS infections and scarlet fever, warning that children under 10 are most at risk.
Group A strep can cause many types of infections, some relatively minor. Strep A, or group A streptococcus, is a bacteria found in the throat and on the skin that usually causes fever and throat infections, such as strep throat or scarlet fever.
More rare are invasive group A strep infections, including necrotizing fasciitis and streptococcal toxic shock syndrome.
Necrotizing fasciitis is sometimes called flesh-eating disease. It's a rare bacterial infection that spreads quickly and can be deadly, according to the CDC. Group A strep is thought to be the most common cause.
Streptococcal toxic shock syndrome, also known as STSS, happens when bacteria spread into deep tissues and the bloodstream. "STSS can develop very quickly into low blood pressure, multiple organ failure, and even death," the CDC says.
Strep A is not fatal for most people who become infected, and antibiotics are usually effective at treating them.
There is no vaccine to prevent strep A infections, and the best way to protect yourself from the bacteria is by washing your hands frequently, the CDC says.
"If someone does get sick from a group A strep infection, timely treatment is important, as it can prevent severe illness and complications," Texas Department of State Health Services spokesperson Lara Anton said Friday.