Confirmed COVID-19 cases have now surpassed 500 million worldwide, according to Johns Hopkins University data.

State of play: The actual number of cases among the world's population of 7.9 billion is believed to be much higher, but many are going unreported — and experts are concerned this will worsen as testing is scaled down in some countries, including the U.S., the New York Times reports.

• There's been an issue throughout the pandemic with lower-income countries having limited public health resources and a lack of coronavirus vaccine access — particularly in Africa, where 21 countries had vaccinated less than 10% of their populations as of February, according to the World Health Organization.

Why it matters: WHO chief Tedros Adhanom Ghebreyesus has stressed that the world is still in the grip of the virus' acute phase. But this could end by the middle of 2022 if 70% of the world is vaccinated, he said.

• Ali Mokdad, an epidemiologist at the University of Washington who previously worked at the Centers for Disease Control and Prevention, told the NYT that a lack of tests creates a "dangerous" situation.
• "If you don't test, then you don’t know what variants you have," Mokdad said.

The big picture: Although coronavirus cases have been trending downward in recent weeks in the United States and across the world, half of U.S. states are seeing infection numbers rise again, with the Omicron subvariant BA.2 accounting for almost three out of every four cases, Axios' Tina Reed and Kavya Beheraj write.

By the numbers: In the U.S., 82.1% of the population has had at least one COVID-19 vaccine dose, CDC figures show.

• About 65% of the world's population has had at least one dose, according to the Our World in Data project at the University of Oxford. In low-income countries, that figure falls to 14.8%.
• As of Wednesday, nearly 500,364,000 COVID infections have been confirmed worldwide since the pandemic began, along with nearly 6.2 million deaths, according to Johns Hopkins. The U.S. has recorded nearly 80.5 million cases and over 986,400 deaths from the virus.