COVID-19 live updates: 'Extremely unlikely' virus came from Chinese lab, WHO says

U.S. Secretary of Transportation Pete Buttigieg is self-quarantining after a member of his staff contracted COVID-19, his office announced Monday.

An agent who is part of Buttigieg's security detail and has close contact with the newly confirmed cabinet member, as recently as Monday morning, tested positive for COVID-19, according to a statement from U.S. Department of Transportation chief of staff Laura Schiller.

Buttigieg, who has received his first dose of the COVID-19 vaccine, tested negative for the disease on Monday. He will receive his second vaccine dose after the quarantine period, according to Schiller.

"Secretary Buttigieg will take all necessary steps to ensure there is no spread, including quarantining for a period of 14 days and will continue to follow all other CDC guidelines," Schiller said in the statement.

Another member of Buttigieg's security team who was in close contact with the infected agent is also quarantining, according to Schiller.

Hospitalizations for COVID-19 in California have fallen 34% over the past two weeks, Gov. Gavin Newsom said at a Monday press conference at Petco Park in San Diego, which has been turned into a mass vaccination site.

A month ago, the Golden State was logging more than 50,000 newly confirmed cases of COVID-19 each day. On Monday, the daily figure fell to 10,414 while the average testing positivity rate was at 5%, down from 14% last month, according to Newsom.

"Hopeful signs continue," the governor wrote on Twitter Monday.

ABC News' Bonnie Mclean and Alex Stone contributed to this report.

More than 117,000 confirmed cases of COVID-19 among children were reported in the United States last week, representing a 10% increase in cases between Jan. 21 and Feb. 4, according to a report released Monday by the American Academy of Pediatrics and the Children's Hospital Association.

The report, which compiles state-by-state data on infections among kids, found that 2.9 million children have tested positive for COVID-19 nationwide since the start of the pandemic. In total, children represent 12.9% of all cases in U.S. states that report COVID-19 data by age.

ABC News' Arielle Mitropoulos contributed to this report.

Facebook announced Monday a global campaign to promote authoritative COVID-19 sources and push back on disinformation.

The effort will including helping people find out where and when to get vaccinated, expanding the social media company's efforts to remove false COVID-19 information from Facebook and Instagram, and giving $120 million in advertising credits to health ministries, NGOs and UN agencies.

Facebook also said it would provide data for education to help build trust in COVID-19 vaccines, as well as to inform vaccine delivery efforts.

ABC News' Mary Kathryn Burke contributed to this report.