Strep infections have persisted at high levels so far this spring, even compared to pre-pandemic years.
The Centers for Disease Control and Prevention said unpublished data from its national surveillance program show that emergency department visits for regular strep infections reached a five-year high in February and March.
A report from Epic Research, which analyzes electronic health records, suggests that in February, rates of strep throat were nearly 30% higher than during the previous peak in February 2017.
Preliminary data suggests the upward trend continued in March, the group told NBC News.
The CDC was unable to confirm Epic's statistics since it does not have data on regular strep infections dating back to 2017.
But Dr. Michael Cappello, vice chair of pediatrics for Advocate Children’s Hospital in the Chicago area, said that compared to pre-pandemic levels, "we’re definitely seeing more run-of-the-mill strep throats, without a doubt."
Strep rates are normally highest from December through April, but doctors last year started seeing cases as early as September.
Rates of invasive group A strep infections have also been higher than usual. Unlike ordinary strep, invasive cases are severe and sometimes life-threatening; they occur when bacteria spread to areas of the body that are normally germ-free, such as the bloodstream, lungs, joints or bones.
A CDC spokesperson said Wednesday that "many states are continuing to see higher than usual numbers of invasive group A strep cases, particularly in children ages 17 years and younger and adults ages 65 years and older."
The CDC issued a health alert in December about the increase in pediatric cases of invasive group A strep infections.
An 'unprecedented' rise in invasive strep A
Dr. Maureen Ahmann, a pediatrician at Cleveland Clinic Children’s, said her practice has seen a considerable increase in invasive strep A cases.
"It’s still rare compared to all the other childhood illnesses, but we are seeing a bump," Ahmann said.
The U.S. records several million cases of noninvasive group A strep per year, but just around 14,000 to 25,000 invasive infections, according to the CDC. Between 1,500 and 2,300 people die of the invasive cases every year.
Dr. Sam Dominguez, an infectious disease specialist at Children’s Hospital Colorado and a professor at the University of Colorado School of Medicine, said his hospital saw about 80 cases of invasive strep from October to March. By contrast, there were about five to 10 cases annually in pandemic years and roughly 20 per year before that, he said.
"We have seen really an unprecedented rise in group A strep — more than we’ve probably seen here, looking back, at least for a decade, and probably longer than that," Dominguez said.
Invasive strep can trigger skin infections like flesh-eating disease, lower airway infections like pneumonia, or streptococcal toxic shock syndrome, an immune reaction that can lead to organ failure. The CDC has recorded 117 cases of streptococcal toxic shock syndrome so far this year, compared to a total of 45 last year.
Why haven’t strep cases gone down?
Epic Research’s findings, which have not been peer-reviewed, were based on doctors' office and emergency room visits across more than 1,100 hospitals and 24,900 clinics in the U.S., as well as one health organization in Lebanon, where the group also collects data.
According to the report, strep throat was most common in children ages 4 to 13, but all age groups have seen an increase.
Doctors have a few theories as to why strep infections have persisted at high levels.
One is that cases declined during the pandemic due to Covid mitigation measures, which then left people more susceptible later. A second possible factor is the respiratory virus surge the U.S. saw this winter. Cappello said those viral infections can weaken people's immune systems or irritate the protective lining of the nose, mouth and throat, making it easier to develop strep.
"The other possibility is, maybe this is a different strain of group A strep that we haven’t seen," Cappello said.
But doctors are optimistic that cases will soon decline. Dominguez and Cappello said their hospitals have seen fewer cases of invasive strep so far in April than in prior months.
"I’m hopeful that means we’re on a downswing," Cappello said.
Antibiotic shortages pose a challenge
The high rate of strep infections has been extra difficult because of a shortage of the antibiotic amoxicillin. The Food and Drug Administration reported a shortage of a powder version of the drug in October, which has not yet resolved.
Ahmann said some Ohio parents struggled to fill their kids' liquid amoxicillin prescriptions.
"It got to the point a month ago, if we needed liquid amoxicillin, we would actually print out the script and give it to the parent and say, 'Listen, last I heard, so-and-so down the road had this, but if they don’t, try here,'" Ahmann said. "The parents would literally go from pharmacy to pharmacy looking for someone who has it."
But she added that, anecdotally, the shortage finally seems to be easing.
Doctors recommend getting kids tested for strep if they have red or sore throats that make it painful to swallow, a fever, swollen lymph nodes or rashes.
"If your child is suddenly not communicating with you, difficult to arouse, incoherent, working really hard to breathe, those kinds of things, that's definitely a trip to go to the emergency room right away," Cappello said.