“We don’t necessarily know if there are actually fewer symptoms in the very young population,” she said.
Similarly, it remains unclear why the study found that young people were more prone to some of the most serious cardiac complications in the first MIS-C wave from March 1 to July 1, 2020. Dr. DeBiasi said this was inconsistent with the experience of her hospital where “the children in the second wave were sick”.
The study documented two waves of MIS-C cases that followed an increase in total coronavirus cases by about a month or more. “The recent third peak of the Covid-19 pandemic appears to be leading to yet another MIS-C peak that may involve urban and rural communities,” the authors wrote.
The study found that most of the states where the rate of MIS-C cases per population was highest were in the northeast, where the first cases arose, and in the south. In contrast, most states with high per-population rates of children with Covid-19 but low MIS-C rates were in the Midwest and West. While the concentration of cases has spread from large cities to small towns over time, it has not been as pronounced as general pandemic trends, the authors said.
Dr. Blumenthal said the geographic pattern could reflect that “understanding the complications of the disease” has not reached its prevalence in different regions, or that many states with lower MIS-C rates have fewer ethnically diverse populations. “It could also be something about Covid itself, although we don’t know,” she said. “At the moment we don’t know anything about how the variants necessarily affect children.”
The study set only the strictest criteria for MIS-C, with the exception of approximately 350 reported cases that met the CDC definition of the syndrome but tested negative for antibodies or primarily related to respiratory symptoms. Dr. DeBiasi said there are also many likely MIS-C cases that are not reported to the CDC because they do not meet all of the official criteria.
“Those likely MIS-C kids, in real life that’s a huge part of the kids,” she said. While the focus so far has been on serious cases, “there is another whole group of children who may actually have mild MIS-C.”
If a community has had a recent spike in coronavirus, it doesn’t mean the child in front of you doesn’t have a MIS-C. Said Dr. DeBiasi. “If your city has Covid, get ready.”
