Severe COVID-19-linked syndrome may be undercounted in U.S. children

Over the course of the pandemic, Texas Children’s Hospital has cared for more than 150 young patients with a rare and sometimes deadly inflammatory condition linked to COVID-19.

The Houston institution is one of more than a dozen children’s hospitals in the state. Yet for all of Texas, the U.S. Centers for Disease Control and Prevention has tallied fewer than 100 cases of children with the condition, called multisystem inflammatory syndrome in children, or MIS-C.

“If our hospital has seen well over 150, then clearly that number is not accurate,” said Lara Shekerdemian, chief of critical care at Texas Children’s. About three-quarters of the kids who suffer from it in her hospital wind up in intensive care, she said.

COVID-19 cases overall are going down in the U.S., according to the CDC, but data on the life-threatening inflammatory response are less clear cut. The numbers are updated monthly, and even then there is a significant lag. The CDC says 3,742 children have been diagnosed with MIS-C in the U.S. since early in the pandemic. That number is likely low – the agency says it’s not performing a comprehensive count.

That’s disquieting news for parents of unvaccinated children younger than 12 or for those of adolescents who have yet to get their shots. Most MIS-C cases have shown up in children from ages 5 to 14, with a median age of 9, according to the CDC.

The data lag is caused by a voluntary reporting system that relies on overburdened hospitals and state health departments, which sometimes report cases late or not at all. Doctors and health officials also need time to determine whether a child truly meets the complicated definition of a MIS-C diagnosis.

While some health departments have reported totals that appear in line with the CDC’s data, large states such as New York, California and Texas show discrepancies.

New York’s Department of Health says it’s investigating 498 reported cases of MIS-C. Yet the CDC reports New York has had only between 100 and 149 cases since reporting began last year. California’s numbers are especially obscure because the CDC lists the state only as having more than 300 MIS-C cases.

Los Angeles County’s health department alone has reported 186 children with MIS-C. The CDC doesn’t view the data on its website as a complete tally, said spokeswoman Jade Fulce. Instead, the agency uses it to understand trends.

MIS-C started as mystery, afflicting children who were otherwise healthy. Early in the pandemic, doctors assumed it was Kawasaki disease, which causes inflammation in blood vessels. They soon determined the children showing up in emergency rooms with swollen hands, bloodshot eyes and blue lips also had fairly recent COVID-19 infections.

MIS-C has dramatic and frightening symptoms. Then it gets worse. Children often go downhill rapidly as the body’s attempt to fight off the illness drives its protective response into overdrive. MIS-C, at its most intense, inflames critical organs, including the heart, lungs, brain and gastrointestinal system, according to the CDC.

“It’s like a bomb is inside them breaking up every part of their immune system,” said Guliz Erdem, a pediatric infectious diseases physician at Nationwide Children’s Hospital in Ohio who has tended to MIS-C patients as young as 2 months old. “This is new territory for everyone involved, and it’s probably the tip of the iceberg.”

Federico Laham, medical director for children’s infectious diseases at Orlando Health Arnold Palmer Hospital for Children in Florida, has treated 40 MIS-C patients. He said conditions like MIS-C, which can’t be confirmed by a laboratory test, typically go underreported. “It also has a very clunky definition,” he said, and doctors may continue to confuse it with Kawasaki disease or toxic shock syndrome if they’re not familiar with newly emerging research.

Most children appear to fully recover after treatment for severe COVID-19 or MIS-C, though the CDC has counted 35 deaths from MIS-C in the U.S. The long-term effects are unclear, said Margaret Aldrich, director of infection control for the Children’s Hospital at Montefiore in New York’s Bronx borough. “There is still a lot about COVID that we do not understand,” she said. “It shouldn’t be discounted as an infection that is not a big deal.”

The CDC has lagged before on data about kids and COVID-19. In July, the CDC was still using figures showing children represented 2% of U.S. virus cases. As testing became more available, state data showed those younger than 18 made up nearly 10% of cases in places like California and Mississippi. Children now represent 24% of new weekly COVID-19 cases, according to the American Academy of Pediatrics.

The academy said that almost 49,000 new cases of COVID-19 in kids were reported the week of May 6. Adrienne Randolph, a Boston Children’s Hospital doctor leading a CDC-funded study on MIS-C that includes pediatric hospitals throughout the U.S., said she believes CDC’s MIS-C numbers are low. “How much lower, I don’t know,” she said.

The reporting process is different in each state, so, by the time the CDC gets its data, it’s no wonder the numbers are off. In Massachusetts, Randolph said, state officials direct hospitals to report suspected MIS-C cases to them. Then, the state determines whether they meet MIS-C criteria and passes those numbers on to the CDC. “That takes time, too, for them to go through them all,” she said. “You can see how easy it would be to get behind.”