The Fresno County Health Department and Valley Children's Hospital have reported seeing an upward trend in the number of cases of Multisystem Inflammatory Syndrome in Children (MIS-C).
The Central Valley's first cases of MIS-C started showing up in the spring of 2020.
"It's become evident that this is a reality that Valley Children's Hospital has been dealing with, really since the start of the pandemic," said Fresno County health officer Dr. Rais Vohra.
MIS-C affects children of any age and usually shows up while a child or a family member is sick with COVID or in the weeks afterwards even if the child never had any symptoms of the virus.
They'll develop seemingly unrelated symptoms - including high fever, abdominal pain, neck pain, and low blood pressure - and the symptoms will get worse fast as the inflammation spreads to organs.
"Creating like a cascade of inflammation and really triggering a storm in the body," said Dr. Reshma Patel, a pediatric rheumatologist at Valley Children's Hospital.
Doctors at Valley Children's have treated more than 100 of about 400 known cases in California.
Fresno County is reporting a concerning increase in Multisystem Inflammatory Syndrome in Children (MIS-C), which is usually connected to COVID-19.@CareForKids has handled about 1/4 of all the state's 400 cases and the number is increasing recently.— Corin Hoggard (@corinhoggard) April 15, 2021
They say it comes in waves, usually after the holidays when COVID infections spread. So they're watching for it now that schools are reopening or coming back from Spring Break.
They say schools following universal masking guidelines have shown lower rates of transmission, but kids need to remember to keep their guard up.
"If you take off your mask to eat lunch with a friend or something and you're sharing that shared space and you're close in proximity and then masks are not on, that's where transmissions happen," said Dr. Hailey Nelson, a Valley's Children's pediatrician.
Dr. Nelson says parents can also help protect their children by protecting themselves.
"Certainly putting that plug in for parents as a way to protect their children: If they are vaccinated, parents are not going to bring the virus home to their children," she said.
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The CDC says MIS-C tends to have more impact in minority communities.
36 kids have died from it in the U.S.
Doctors at Valley Children's say they haven't seen any deaths, but they're sending out a warning now and monitoring whether the condition leads to any long term effects.