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 New York City health care provider under investigation for allegedly misappropriating the Moderna coronavirus vaccine, told ABC News it will return its vials to the state Health Department.

The New York State Department of Health is currently probing ParCare, which has offices in Brooklyn, to determine if it misused what was an approved allocation toward members of the public not yet prioritized under current New York guidelines.

Under the current state rules, only medical workers, first responders and nursing home staff members are allowed to receive any coronavirus vaccine. Other groups will follow in future rounds.

ParCare touted the vaccine on its social media pages with a flyer that claimed the vaccines would be available on a "first come, first serve basis."

"We have set up a special system where you can reserve your slot. This will enable you to receive the vaccine as soon as it arrives to the center," the flyer said.

The flyer also claimed that the vaccines were only for people who were "elderly," "high risk" or "underlying conditions."

New York state police and other investigators were at the ParCare location in Borough Park on Saturday night.

A spokesman for ParCare told ABC News Sunday evening that it is cooperating with the state investigation and will return its unused vials.

ParCare received 2,300 doses of the Moderna vaccine, and 869 of those doses have already been administered, according to the spokesperson.

"ParCare followed all NYS DOH procedures for obtaining the Moderna vaccine and was approved by NYS DOH for distribution and by CDC as a network site. As a result, we have properly received the vaccines and have provided the documentation regarding the proper receipt of the vaccines to the NYS DOH," the spokesperson told ABC News.

With regards to the patients who received their first shot, ParCare said it will be "working with the state to ensure that we provide the second dose for our patients."

-ABC News' Sasha Pezenik and Aaron Katersky contributed to this report