Japan is no longer the best-performing wealthy nation when it comes to avoiding COVID-19 deaths.

The country, which has one of the oldest populations in the world, is quietly experiencing its biggest outbreak of the pandemic. A wave of omicron infections overwhelmed its health system this winter and delayed medical care for patients, sending daily deaths to a record high of more than 500 on Jan. 14, according to data compiled by Bloomberg.

The increase pushed Japan’s overall mortality rate above New Zealand’s, which now has the fewest deaths per capita among the OECD's 38-member countries, according to Our World in Data. Infection rates in Japan, while still among the lowest in the world, rose rapidly in recent months.