Scientists now have some clues about the cause of Kawasaki disease, a rare inflammatory disease that can affect very young children.

Doctors say it’s important to recognize the signs of the condition as local hospitals see an increase in cases.

3-year-old Hannah developed a fever in November. Her mother, Karen Ho, thought it was a minor illness.

“We all thought she had hand, foot and mouth disease. There was an outbreak at her kindergarten,” she said.

But Hannah’s fever lasted for five days, rising to 104 degrees. This is followed by a rash and swelling of the legs.

“When she woke up the next morning, her eyes and lips were red,” Ho said. Her pediatrician recognized the classic signs.

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“I could see her demeanor change. It was like she needed to bring in a lab right away. I really hope it’s not Kawasaki,” she said.

In Kawasaki disease, the blood vessels that carry oxygen to the heart swell and become inflamed. This condition mainly affects children under the age of 5.

“It is the leading cause of acquired heart disease in children, rather than congenital heart disease,” said Dr. Moshe Arditi of Cedars-Sinai Guerin Children’s Center.

Without prompt treatment, heart problems can last a lifetime. Although rare, Arditi said the number of patients at the hospital has increased by 50% in the past four months.

“Usually we have two to three cases. And right now, we’ve already seen six cases.”

but why? The cause is a mystery, but new evidence suggests the cause may be an infectious agent that affects genetically susceptible children. During the pandemic, Arditti observed a dramatic drop in cases in Kawasaki.

“It’s because of mask-wearing and social distancing and all the measures that we’ve taken,” he said.

The treatment for Kawasaki disease is intravenous immunoglobulin called IVIG. If given early, patients usually make a full recovery.

For Hannah, the effects were immediate.

“She was running around the hospital like she was playing on the playground,” she said.

However, in 20% of children, IVIG does not work. Arditi’s team is investigating treatments that block inflammatory proteins that prevent further blood vessel damage.

“You can really reduce your child’s chances of developing long-term heart disease.”

The chance of getting Kawasaki disease twice is about 2%. But in March, Hannah was diagnosed again. Prompt treatment was equally effective the second time. Her mother told her to know her symptoms and tell her doctor.

“It doesn’t feel like something is normal. It’s like you have to take your child with you,” Ho said.