Is the delta variant more dangerous for children? A growing number of kids are very sick

The number of very sick children admitted to Children's Hospital New Orleans with Covid-19 has exploded over the past two weeks — from zero to 20.

"I've never seen anything like it," said Dr. Mark Kline, the hospital's physician-in-chief. "We are seeing children fall ill that we just simply didn't see in the first year of the pandemic, before the delta variant came along."

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Doctors at Orlando Health Arnold Palmer Hospital for Children Infectious Diseases in Florida have seen similar surges recently. "The last two weeks, cases have continued to increase," said Dr. Federico Laham, medical director for the hospital. "I don't think we have reached our peak."

Despite the dramatic increase in cases, Laham and other pediatric infectious disease experts nationwide tell NBC News that there is no hard evidence yet that the delta variant has transformed the virus into something more dangerous in kids.

"It's too early to tell," said Dr. Bernhard Wiedermann, an infectious diseases specialist at Children's National Hospital in Washington, D.C. "It's going to take time and a collection of data from multiple sites to know" whether the delta variant is, in fact, more virulent in kids than previous versions of the virus.

The Centers for Disease Control and Prevention is working to determine whether the delta variant can, in fact, cause more severe disease in children, Dr. Rochelle Walensky, the CDC's director, said during a briefing Thursday.

She added that such research is complicated by the combination of increased cases and relaxed restrictions on masking and physical distancing. "The mitigation strategies that were used last summer, even in the winter, have not been employed in many of these areas that we are having surges right now," Walenksy said.

Delta is a doctor's 'worst nightmare'

What is obvious now, experts say, is that surges in pediatric cases are due to the variant's hypertranmissibility, circulating in a population left unvaccinated and therefore vulnerable to the virus.

"If more children get sicker, that's just because more kids are getting sick," said Dr. Paul Offit, a vaccine researcher at the Children's Hospital of Philadelphia. "It's clearly increased contagiousness, not increased virulence."

Children have been susceptible to Covid-19 all along. More than 4.1 million children have been diagnosed with Covid-19 since the beginning of the pandemic, accounting for 14.3 percent of all cases, according to the latest data from the American Academy of Pediatrics.

From July 15 to July 29, that percentage rose to 19 percent of weekly reported cases.

"Over the course of the first year of this pandemic, the myth existed that children never got very ill from Covid," Kline said. That was mainly because the number of pediatric cases was relatively low.

Because the delta variant is so contagious, he said, the increase in cases clearly shows the virus's potential, even in young, otherwise healthy children.

"This delta variant is an infectious disease specialist's worst nightmare," Kline said.