SAN FRANCISCO (KGO) -- After four years of research and close to 200 blood samples from children across the country, San Francisco researchers have cracked the case. They now have an answer to a mysterious severe illness that put many children on the verge of dying. ABC7 News reporter Luz Pena went to the lab where this discovery took place.

It was 2020 when Dr. Aaron Bodansky was seeing a high number of children coming into the ICU with a mysterious inflammatory disease. "They had very high fevers, they had severe inflammation of all their bodies, but in particular, their lungs and really their hearts.

It made it so their hearts were not able to pump enough blood to keep them alive," said Dr. Bodansky, assistant professor of UCSF pediatric critical care. The illness came to be known as Multi-System Inflammatory Syndrome in Children, or MIS-C.

"The scariest part of it was that we couldn't explain at all what was causing the disease. The only thing we knew was that they previously had a SARS-CoV-2 infection. Then about a month later, they would get this mysterious severe illness that put them on death's door," said Dr.

Bodansky. MORE: Small study shows a possible reason some long COVID patients experience 'brain fog' As cases intensified, doctors suspected the severe inflammation was connected to the immune system. "We used medicines to suppress and calm their immune system which thankfully worked extremely well to save their lives," said Dr.

Bodansky. Dr. Bodansky remembers r.