According to the coronavirus resource center at Johns Hopkins University, the number of deaths from COVID-19 topped 5 million worldwide Monday. Just over 746,000 of those deaths are attributed to the United States. As of early Monday afternoon, worldwide cases were approaching 247 million, with just under 46 million of those being in the U.S.

The worldwide death toll is about equal to the populations of Los Angeles and San Francisco combined. COVID-19 is now the third leading cause of death around the world, after heart disease and stroke.

“This is a defining moment in our lifetime,” infectious disease specialist Dr. Albert Ko said. “What do we have to do to protect ourselves so we don’t get to another 5 million?”

The 5 million COVID-19 deaths worldwide are believed to be an undercount due to limited testing, as well as people dying at home. This happens at significantly higher rates in poorer parts of the world.

COVID-19 deaths hit the grim milestone a day after White House press secretary Jen Psaki said she has contracted a breakthrough case of COVID-19. The press secretary said she is experiencing mild symptoms.

“On Wednesday, in coordination with senior leadership at the White House and the medical team, I made the decision not to travel on the foreign trip with the president due to a family emergency, which was members of my household testing positive for COVID-19,” Psaki said in a statement on Sunday. “Since then, I have quarantined and tested negative (via PCR) for COVID on Wednesday, Thursday, Friday and Saturday.”

Psaki went on in the statement to say she had last seen President Joe Biden, “on Tuesday, when we sat outside more than six feet apart and wore masks.”

White House staff and others traveling with the president have been undergoing daily tests for COVID-19 since before departing Washington and are all fully vaccinated. Biden himself last tested negative Sunday, according to White House principal deputy press secretary Karine Jean-Pierre.