NEW YORK (Reuters) - The United States on Monday crossed the staggering milestone of 500,000 COVID-19 deaths just over a year since the coronavirus pandemic claimed its first known victim in Santa Clara County, California.

In a proclamation honoring the dead, President Joe Biden ordered the U.S. flag to be flown at half-staff on public buildings and grounds until sunset on Friday.

"On this solemn occasion, we reflect on their loss and on their loved ones left behind," Biden said in the proclamation. "We, as a Nation, must remember them so we can begin to heal, to unite, and find purpose as one Nation to defeat this pandemic."

Bells tolled at the National Cathedral in Washington to honor the lives lost - ringing 500 times to symbolize the 500,000 deaths.

Newsletter signup for email alerts

“As we acknowledge the scale of this mass death in America, remember each person and the life they lived," Biden said in a somber speech at the White House after the bells sounded.

"The son who called his mom every night just to check in. The father, the daughter who lit up his world. The best friend who was always there. … The nurse who made her patients want to live."

A few moments later, Biden, Vice President Kamala Harris and their spouses appeared wearing black clothing and black masks. They stood silently as the hymn "Amazing Grace" was played.

President Joe Biden, his wife Jill Biden, Vice President Kamala Harris and Second Gentleman Doug Emhoff attend a moment of silence and candle lighting ceremony to commemorate the grim milestone of 500,000 U.S. deaths from the coronavirus disease (COVID-19) at the White House in Washington, Feb. 22. REUTERS / Jonathan Ernst
President Joe Biden, his wife Jill Biden, Vice President Kamala Harris and Second Gentleman Doug Emhoff attend a moment of silence and candle lighting ceremony to commemorate the grim milestone of 500,000 U.S. deaths from the coronavirus disease (COVID-19) at the White House in Washington, Feb. 22. REUTERS / Jonathan Ernst

The country had recorded more than 28 million COVID-19 cases and 500,264 lives lost as of Monday afternoon, according to a Reuters tally of public health data, although daily cases and hospitalizations have fallen to the lowest level since before the Thanksgiving and Christmas holidays.

About 19% of total global coronavirus deaths have occurred in the United States, an outsized figure given that the nation accounts for just 4% of the world's population.

"These numbers are stunning," Dr. Anthony Fauci, a top infectious disease adviser to President Joe Biden told ABC's "Good Morning America" program. "If you look back historically, we've done worse than almost any other country and we're a highly developed, rich country."

In an interview with Reuters on Monday, Fauci said political divisiveness contributed significantly to the U.S. death toll.

More vigilance urged

The country's poor performance reflects the lack of a unified, national response last year, when the administration of former President Donald Trump mostly left states to their own devices in tackling the greatest public health crisis in a century, with the president often in conflict with his own health experts.

In 2020, the virus has taken a full year off the average life expectancy in the United States, the biggest decline since World War Two.

Sweeping through the country at the beginning of last year, the U.S. epidemic had claimed its first 100,000 lives by May.

The death toll doubled by September as the virus ebbed and surged during the summer months.

Pandemic-weary Americans, like so many around the world, grappled with the mountain of loss brought by COVID-19 as health experts warned of yet another coronavirus resurgence during the fall and winter months.

Americans lost mothers and fathers, husbands and wives, brothers, sisters and friends to the virus. For many, the grief was amplified by the inability to see loved ones in hospitals or nursing homes and by the physical distancing imposed by authorities to curb the virus spread.

By December, the death toll had reached 300,000 in the United States. In the three months after Thanksgiving, the virus would claim 230,000 lives.

With numbers that made the appalling toll early in the pandemic pale by comparison, deaths recorded between December and February accounted for 46% of all U.S. COVID-19 fatalities, even as vaccines finally became available and a monumental effort to inoculate the American public got started.

Despite the grim milestone, the virus appears to have loosened its grip as COVID-19 cases in United States fell for the sixth consecutive week. Health experts have warned, however, that coronavirus variants initially discovered in Britain, South Africa and Brazil could unleash another wave that threatens to reverse the recent positive trends.

In his White House remarks, Biden called on Americans to remain vigilant in fighting the pandemic by continuing to wear masks, observe social distancing and receive vaccinations when it is their turn.