Coronavirus Watch: This state is the newest hot spot in the US

Missouri has the nation's highest rate of new COVID-19 infections.

Experts say the surge is due to a combination of the fast-spreading delta variant and resistance among many people to getting vaccinated. While over 53% of all Americans have received at least one shot, according to the CDC, most southern and northern Missouri counties are well short of 40%. One county is at just 13%.

The delta variant "literally took three weeks to sweep the state," Marc Johnson, professor of molecular biology and immunology in the University of Missouri School of Medicine, told the USA TODAY Network. The variant now accounts for 20% of U.S. active cases, the CDC said.

It's Thursday, and this is the Coronavirus Watch from the USA TODAY Network. Here's more news you need to know:

• San Francisco is requiring all city workersto receive the COVID-19 vaccine once the FDA gives it full approval. It is the first city and county in California, and possibly the U.S., to mandate vaccinations for city workers.
• The pandemic has widened the life expectancy gap between the U.S. and other high-income countries, a new study shows, and experts say it could take decades to overcome.
• California’s vaccination rate rose throughout the beginning of June, according to a Los Angeles Times data analysis, right after Gov. Gavin Newsom announced a $116.5 million incentive program.
• The U.S. will send three million doses of Johnson & Johnson’s vaccine Thursday to Brazil, which just crossed 500,000 deaths this week, according to the White House.
• Israel’s government postponed the planned reopening of the country to vaccinated tourists over concerns about the spread of the delta variant.
• Australia's largest city is facing increased pandemic restrictions as a cluster of the delta variant spreads. Residents are now being asked to stay at home, gatherings are limited to five people and mandatory mask wearing has been reinstated, according to the New York Times.

Today's numbers: The U.S. has reported more than 33.5 million COVID-19 cases and 602,000 deaths, according to data from Johns Hopkins University. Worldwide, there have been more than 179.6 million cases and more than 3.9 million deaths. Nearly 54% of people in the U.S. have received at least one vaccine shot, and about 45% are fully vaccinated, according to the CDC.

Tracking the pandemic: See the numbers in your area here. See where cases are rising here. See vaccination rates here. And here, compare vaccinations rates worldwide and see which countries are using which vaccines.

– Grace Hauck, USA TODAY breaking news reporter, @grace_hauck