World Health Organization (WHO) Director-General Tedros Adhanom Ghebreyesus on Wednesday said that more cases had been reported to the agency in the last 24 hours than any time since the novel coronavirus outbreak began.

"We still have a long way to go in this pandemic," Tedros said at a briefing in Geneva. "In the last 24 hours, there have been 106,000 cases reported to WHO – the most in a single day since the outbreak began. Almost two-thirds of these cases were reported in just four countries."

Tedros also acknowledged having received a letter from U.S. President Donald Trump, but declined to comment further. "The answer is simply we have received the letter and are looking into it," he said.

Trump published a letter to Tedros on Monday which gives the WHO a 30-day ultimatum to overhaul its operations. Otherwise its biggest contributor would freeze its funding and consider pulling out altogether.

As of Wednesday, the global coronavirus cases have surpassed 5 million, with Latin America overtaking the United States and Europe in the past week to report the largest portion of new daily cases globally.

It represents a new phase in the spread of the virus, which initially peaked in China in February, before large-scale outbreaks followed in Europe and the United States.

Latin America accounted for around a third of the 91,000 cases reported earlier this week. Europe and the United States each accounted for just over 20 percent.

A large number of those new cases came from Brazil, which recently surpassed Germany, France and the United Kingdom to become home to the third-largest outbreak in the world, behind the United States and Russia.

Cases in Brazil are now rising at a daily pace second only to the United States.

The first 41 cases of coronavirus were reported in Wuhan, China, on January 10 and it took the world until April 1 to reach its first million cases. Since then, about 1 million new cases have been reported every two weeks, according to a Reuters tally.

At more than five million cases, the virus has infected more people in under six months than the annual total of severe flu cases, which the WHO estimates is around three million to five million globally.

The pandemic has claimed over 326,000 lives, though the true number is thought to be higher as testing is still limited and many countries do not include fatalities outside of hospitals.

Over half of the total fatalities have been recorded in Europe. Despite the continued increase in cases, many countries are opening schools and workplaces following weeks of lockdown that have largely stemmed the spread of the virus.

Financial markets have also been boosted slightly by promising early results from the first U.S. vaccine trial in humans.

(With input from agencies)