The novel coronavirus pandemic has reached a new milestone, with more than 12 million confirmed infections, according to the online tracker created by Johns Hopkins University.

The United States leads the world with most confirmed coronavirus infections with 3,054,695 -- a quarter of the world's total -- including more than 60,000 new cases on Wednesday, the biggest single-day number since the outbreak began.

At least five states -- California, Texas, Tennessee, West Virginia and Utah -- posted a record number of new cases Wednesday, while several states reached records for new cases over a seven-day period. Health officials in Arizona, California, Florida and Texas are also warning that hospitals across their states have reached or are nearing full capacity in their intensive care units.

Meanwhile, residents in Australia's second-largest city of Melbourne entered into a six-week lockdown at midnight local time Wednesday due to an alarming spike of new COVID-19 cases. Residents have been ordered to stay home unless going to work, school, medical appointments or shopping for food. City officials had already imposed stay-at-home orders in at least 30 neighborhoods and a "hard" lockdown of nine public housing towers, home to over 3,000 residents, where 23 COVID-19 cases have been detected among 12 households.

The total lockdown comes just days after officials in the neighboring states of Victoria and New South Wales closed their shared border after Melbourne, Victoria's capital city, reported 127 new coronavirus cases on Monday.

In Japan, public broadcaster NHK is reporting that Tokyo has recorded 224 new cases of coronavirus infections on Thursday, a new one-day record for the capital city.

A new study published Wednesday in the scientific journal Nature has found that older people, men, racial and ethnic minorities and those with preexisting health conditions such as obesity, diabetes and severe asthma are more likely to die from COVID-19.

The study was conducted by a team of British researchers who tracked over 17 million people over three months. They found that of the more than 10,000 people who died of COVID-19 or COVID-19-related complications, patients 80 years old or older were a least 20 times more like to die from the disease than those in their 50s, and hundreds of times more likely to die than those below the age of 40.

The researchers also found that roughly 11 percent of the total number of people tracked in the survey identified as non-white, and that these patients -- particularly Black and South Asian -- were at higher risk of dying from coronavirus than white patients.