The director-general of the World Health Organization, Dr. Tedros Adhanom Ghebreyesus, said Tuesday the coronavirus outbreak is “accelerating, and we have clearly not reached the peak of the pandemic.”

“More than six months in, the case for national unity and global solidarity is undeniable,” he said at a WHO briefing Tuesday. “We cannot afford any divisions.”

Tedros stressed that while global deaths have leveled off, many countries are actually seeing cases and deaths rise. Dr. Mike Ryan, executive director of WHO’s Health Emergencies Program, said there are several possible explanations for a global death decline. One explanation, he said, could simply be that there’s a lag, and we may see deaths rise again.

Ryan warned, however, that what is imminently concerning is a daily increase in cases. “That is not purely a result of testing,” he said. According to Tedros, a team of WHO experts will be traveling to China this week to advance research working to understand how the novel coronavirus first reached humans.

Ryan said understanding how the virus got from the animal kingdom to humans is an “extremely important” step in managing risk going forward. “There is a trail and we have to follow that,” he said.  They spoke after scientists urged the agency and other public health organizations to amend their guidelines to reflect the risk that the coronavirus can be airborne.

The WHO has said the coronavirus is only confirmed to be airborne during aerosol-generating medical procedures performed in health care settings, such as intubation. It says the virus primarily spreads through larger respiratory droplets, which don’t travel as far, which is why maintaining social distancing of about 6 feet has been recommended. But an open letter supported by 239 scientists says airborne transmission of COVID-19 is a “real risk.” 

“Hand washing and social distancing are appropriate, but in our view, insufficient to provide protection from virus-carrying respiratory microdroplets released into the air by infected people,” states the letter, entitled “It is Time to Address Airborne Transmission of COVID-19.”  

On Tuesday, WHO’s COVID-19 technical lead, Dr Maria Van Kerkhove, said the organization is in the process of producing a scientific brief on the issue that will be published in the coming days. She said the WHO still recommends people physical distance and continue to wear face masks. The letter was issued as the United States sees a spike in coronavirus cases. Dr. Anthony Fauci, the nation’s top infectious disease expert, said Monday the country is still “knee-deep” in the first wave of the pandemic.