As the COVID-19 pandemic deepens, the World Health Organization said it acknowledges the emerging evidence that the deadly and infectious coronavirus may be transmitted through the air.
During a news briefing on Tuesday, WHO health experts responded to an open letter signed by 239 scientists the day prior urging the U.N. body to recognize the potential for airborne spread of COVID-19 and to adopt measures to prevent such transmission.
Maria Van Kerkhove, an epidemiologist and the WHO's technical lead for COVID-19, said WHO health experts have been reviewing the evidence and discussing the possibility of airborne transmission of COVID-19 and have been working on a scientific brief summarizing their findings to be released in the coming days.
The WHO has said the disease is transferable through droplets, but that form of transmission is different from airborne transmission. Airborne transmission of COVID-19 is possible, the WHO said, under specific circumstances and settings, especially in healthcare facilities, in which procedures or treatments generate aerosols.
In the letter, the scientists said their studies have demonstrated "beyond any reasonable doubt" that COVID-19 is released during breathing, talking and coughing as microdroplets small enough to remain aloft in the air, posing a risk of airborne infection beyond three to 6.5 feet from the infected person, particularly indoors.
The scientists said the reluctance of health organizations, including the WHO, to acknowledge airborne transmission outside those specific healthcare settings is concerning and warned that "the lack of clear recommendations on the control measures against the airborne virus will have significant consequences."
The WHO has had "active engagement" with the group of scientists since they first wrote to the U.N. organization in April, Van Kerkhove said, noting that it is important that what they know about the disease fits into their guidance.
"[A] comprehensive package of interventions are required to stop transmission," she said, adding they are "looking at the role of airborne transmission in other settings."
Benedetta Allegranzi, the WHO's global unit coordinator for infection prevention, said during the briefing that the organization acknowledges there is "emerging evidence" of airborne transmission but "it is not definitive."
"Therefore, the possibility of airborne transmission in public settings, especially in very specific conditions -- crowded, closed poorly ventilated settings -- that have been described, cannot be ruled out," she said. "However, the evidence needs to be gathered and interpreted."
Tedros Adhanom Ghebreyesus, director general of the WHO, said during the briefing that "the outbreak is accelerating and we have clearly not reached the peak of the pandemic." He said the first 400,000 infections of COVID-19 took over 12 weeks and that more than that number of cases were diagnosed over the last weekend.
Tedros also announced a team of WHO experts will travel this weekend for China to prepare a plan with their Chinese counterparts for identifying where the virus came from.
The virus emerged in the central Chinese city of Wuhan late last year, but the United States, Australia and other countries have been calling for an independent probe into its origins following accusations the Chinese government attempted to cover up its initial response to the outbreak, which has since spread the world over infecting nearly 12 million people resulting in more than 544,000 deaths.
China has long claimed that it told the WHO as early as possible about its outbreak but the U.N. body revised its timeline of the pandemic late last month showing that it first learned about the Asian nation's outbreak through a media statement from the Wuhan Municipal Health commission and not directly from Chinese officials.
The United States has accused the WHO of enabling China in its cover up, which was one of the reasons that prompted President Donald Trump on Tuesday to send formal notice to Congress and the United Nations that it was withdrawing from the WHO.
Tedros finished his opening remarks to the meeting Tuesday by calling for unity in the face of the pandemic.
"I will say it again, national unity and global solidarity are important more than ever before to defeat a common enemy, a virus that has taken the world hostage," he said. "This is our only road out of this pandemic. I repeat: national unity and solidarity."