A team of experts from the World Health Organization arrived in the central Chinese city of Wuhan on Thursday to investigate the origins of the COVID-19 pandemic.

The 10-member international team flew into Wuhan after a direct flight from Singapore and immediately entered a 14-day quarantine period. Two other members of the WHO team remained in Singapore after testing positive for COVID-19 antibodies, according to a series of tweets from the agency.

The virus was first detected in Wuhan in late 2019, and eventually spread to nearly every corner of the globe, leading to more than 1.9 million fatalities out of more than 92.3 million total infections, according to Johns Hopkins University Coronavirus Resource Center.

WHO Director-General Tedros Adhanom Ghebreyesus openly expressed "disappointment" with China last week after Beijing failed to grant final permission to the delegation to enter the country, although the plans had been jointly arranged between the two sides. Beijing defended the delay as a "misunderstanding."

The team's arrival comes as China reports its first new COVID-19 death since last May, part of a surge of new coronavirus infections in the northern provinces of Hebei and Heilongjiang. The National Health Commission reported 138 new cases on Thursday, up from the 115 new cases posted just the day before, with Hebei province recording 81 new cases and 43 coming out of Heilongjiang. The other 14 came from outside the country.

The surge of new infections has prompted officials in Hebei province to place several cities in lockdown, while authorities in northeastern Heilongjiang province have declared an "emergency state" for the entire province and its 37 million residents.

The world appears to be on the verge of another effective COVID-19 vaccine. A study published Wednesday in the New England Journal of Medicine found that an experimental vaccine developed by Johnson & Johnson generated a strong immune response in both young and elderly volunteer participants in early-stage trials.

Unlike the vaccines developed by Pfizer-BioNTech and Moderna, the Johnson & Johnson vaccine only requires one dose, making it easier to both transport and refrigerate for long periods of time. The vaccine is currently undergoing late-stage trials involving 45,000 volunteers. Johnson & Johnson is expected to seek emergency use authorization from the U.S. Food and Drug Administration sometime next month.

The company has signed a $1 billion contract with the U.S. government to provide up to 100 million doses of the vaccine once it is granted approval.