An increasing number of children are being infected with multisystem inflammatory syndrome in children (MIS-C), according to a statement Saturday relased by Los Angeles County Board of Supervisors Chair Hilda L. Solis, supervisor to the First District.

"It is heartbreaking that every day, more than 14,000 Los Angeles County residents are testing positive for COVID-19. It is even more painful to see an increasing number of children being infected by MISC-C. There is a misconception that COVID-19 only impacts those who are older or those with underlying health conditions. At this point in the crisis, we can say for certain that COVID-19 causes severe consequences in people of all ages, including children, and even without underlying health conditions. In Los Angeles County, the Latinx community is bearing the brunt of COVID-19 and MISC-C cases," the statement read.

There have been 51 total cases of MIS-C in children, including one child death. All 51 children with MIS-C were hospitalized and nearly 50% of the children were treated in the intensive care unit. Of the children with MIS-C, 31% were under the age of 5 years old, 38% were between the ages of 5 and 11 years old, and 31% were between the ages of 12 and 20 years old. Latinx children account for nearly 73% of the reported cases, according to the statement.

Experts say the inflammatory syndrome resembles toxic shock syndrome and Kawasaki disease, itself a rare inflammatory disease typically affecting children under the age of 5, and has the potential to be deadly.

-ABC News' Matthew Fuhrman, Olivia Rubin and Soo Rin Kim

Madrid health officials confirmed Saturday that four cases of the new variant of COVID-19 already detected the U.K, have been discovered in Spain, Reuters reported.

The new variant has also been detected in Sweden after a traveler from Britain fell ill on arrival and tested positive for it, the Swedish Health Agency said on Saturday, according to Reuters.

"The employee received the Moderna vaccine Thursday and as is our standard practice was being observed post vaccination by trained nurses. He felt he was developing an allergic reaction and was allowed to self-administer his personal epi-pen. He was taken to the Emergency Department, evaluated, treated, observed and discharged. He is doing well today," Boston Medical Center said in a statement to ABC News.

- Aaron Katersky

Despite health official warnings to stay home this holiday season, and while overall air travel is down nearly 60% from this time last year, the Transportation Security Administration's numbers have jumped, showing more than 7 million people hitting the skies in the past seven days, according to a "Good Morning America" report Saturday.

Over 7.8 million travelers were screened by the TSA since last Friday, Dec. 18 -- the busiest stretch of travel since the beginning of the pandemic.

The number of new coronavirus cases and deaths jumped over the last seven days, according to an internal U.S. Department of Health and Human Services memo obtained by ABC News.

In the last week, the country recorded 1,677,232 new cases, which was a 13.6% increase from the previous seven-day period, according to the memo.

There were 18,578 deaths recorded during the last seven days, marking a 9.2% jump from the previous week, according to HHS.

Nearly 30% of hospitals across the country have more than 80% of their ICU beds filled, the memo said.

Several states recorded large jumps in hospitalizations last week, according to HHS.

On Dec 18, Louisiana state officials reported its 30-day increase in hospitalization was 82% and there were only 19.1% of ICU beds were available, according to the memo.

Nevada's COVID-19 deaths increased by 21% in the week ending Dec. 15, compared to the prior week, HHS said.

-ABC News' Josh Margolin contributed to this report