WASHINGTON (BLOOMBERG) - Paediatricians in United States Covid-19 hot spots are anticipating a Delta-fuelled swell of children with a rare, serious and sometimes deadly virus-linked condition as the resumption of school looms.
The condition, called multisystem inflammatory syndrome in children (MIS-C), occurs in a small number of children who have been exposed to the coronavirus. Children can develop the illness even if they have not had Covid-19 symptoms, and week-long intensive care unit stays are not uncommon.
Just discovered last year, MIS-C can wreak havoc on children's hearts as well as their digestive, nervous and respiratory systems. With Delta more than quadrupling paediatric Covid-19 cases in the week ending Aug 5, compared with a month earlier, doctors see an avalanche of the inflammatory disorder on the way.
"When we enter this phase now where potentially millions of children are going to be infected with Covid-19, by default we are going to have very high numbers of MIS-C," said Dr Allison Eckard, a paediatric infectious disease specialist at Medical University of South Carolina Children's Health.
"The percentage of children who are critically ill when they get admitted is unbelievable."
MIS-C appears to be an overreaction by the immune system to Covid-19, though its exact cause is not yet known. The excessive response can damage organs and blood vessels. When first seen, the condition was mistaken for Kawasaki disease, which causes swelling in artery walls throughout the body, sometimes leading to complications like aneurysms, according to US health officials.
A hospital stay for MIS-C patients is usually about a week, doctors said. Many children start off with gastrointestinal symptoms like vomiting and diarrhoea. Early symptoms can also include bloodshot eyes, chest tightness and rash.
Children typically need medication to stabilise their blood pressure, as well as steroids and intravenous immunoglobulin - part of blood plasma that has antibodies in it to treat infection - to protect their hearts from inflammation.
The Delta surge has created a dangerous situation for children. They have typically fared better than adults who are infected with Covid-19, but the impact of MIS-C and long Covid, when some symptoms persist for months or more, is unknown.
Almost 94,000 Covid-19 cases were reported in children the week ending Aug 5, the American Academy of Paediatrics said in its most recent weekly report, up from about 19,500 during the first week in July.
And more children are being hospitalised with Covid-19 than ever before: During the winter surge, the daily number peaked at 217. That number rose to a record high of 246 as at Tuesday (Aug 10), the most recent day the CDC has data for.
As older Americans get vaccinated, the proportion of children among the total Covid-19 count is also growing. In Mississippi, where daily Covid-19 cases have surpassed winter numbers with 2,600 new infections a day, children now represent 21 per cent, up from 15 per cent in January, state health officials said on Wednesday.
"I am really concerned right now about what we may see, and what we are beginning to see, with the incidence of MIS-C again in the context of the increasing proportion of children who are being infected with Sars-CoV-2, especially with children going back to school right now," said Dr Charlotte Hobbs, a paediatric infectious disease specialist who does follow-up care for children treated at the University of Mississippi Medical Centre's MIS-C clinic.
The state's primary paediatric hospital, the centre has been strained by the uptick in childhood Covid-19 cases as well as cases of respiratory syncytial virus, another childhood infection.
Like other Southern states, Mississippi's Covid-19 vaccination rate among those aged 12 and older is low, and use of other prevention measures like masks has become lax.
"If you see a train coming, you get off the tracks, and we just haven't had the foresight to do that," said Dr Thomas Dobbs, Mississippi's state health officer. "We have entered the realm of crisis standard of care. Don't expect if you go into a hospital that they're going to be able to treat you."
The lack of resources is dangerous for MIS-C patients, most of whom need intensive care, Dr Hobbs said.
The median age of children who come down with MIS-C is nine, and half are between five and 13 years old, according to the CDC. The agency has tallied more than 4,400 US cases and 37 MIS-C deaths since early in the pandemic. Those numbers may be shy of the reality, as states only report voluntarily, and sometimes the on-the-ground hospital counts are much higher than the CDC total.
The American Academy of Paediatrics sent a letter last week to the Food and Drug Administration urging the agency "to continue working aggressively towards authorising safe and effective Covid-19 vaccines for children under age 12 as soon as possible".
Both Moderna and the partnership of Pfizer and BioNTech are studying their vaccines in children, and Moderna just doubled the size of its trial in response to a request from US regulators for more safety data.
"The Delta variant really put some urgency on this as we enter the school year," said Dr Sean O'Leary, vice-chairman of the academy's Committee on Infectious Diseases who practices at Children's Hospital Colorado.
"Cases are rising everywhere and it's all over the map what school districts are doing regarding masks."
Dr O'Leary said doctors expect that a Covid-19 shot would offer children protection from MIS-C as well.
"Our kids, especially those too young to receive the vaccine, are some of our most vulnerable patients," said Dr William Orr, a paediatric cardiologist at St Louis Children's Hospital in Missouri.
"These are kids that are completely healthy. The kids that come in with MIS-C, parents are usually shocked. They may not know they were exposed to Covid in the past."
Lack of knowledge
One bright spot is that experience has improved treatment, Dr Orr said. Since the pandemic began, doctors have gained a better understanding of how to treat MIS-C, and children usually recover.
Doctors have been looking for signs of long-term complications in recovered patients, such as heart disease that sometimes appears in children who have had Kawasaki disease.
Dr Thomas Kimball, division chief of cardiology and co-leader of the MIS-C clinic at Children's Hospital New Orleans, has been following 60 to 80 children who had MIS-C previously during the pandemic. So far, he said, that doesn't appear to be the case with the Covid-19-linked condition.
But he plans to continue to follow them "because we just don't know", he said. That lack of knowledge keeps the level of anxiety high at the New Orleans hospital, where 12 Covid-19 patients were in treatment on Tuesday, most of them younger than two years old.
"We're tremendously nervous," Dr Kimball said. "We're anticipating worse MIS-C in terms of number and severity."