The meeting will take place on Thursday, June 23, WHO director general Dr. Tedros Adhanom Ghebreyesu announced at a Tuesday media event.

“It’s now clear there is an unusual situation, meaning the virus is behaving unusually from how it used to behave in the past,” Adhanom Ghebreyesu said. “It’s affecting more and more countries, and we believe that it needs some coordinated response because of the geographic spread.”

The organization doesn’t want to wait to convene a meeting until the situation is “out of control,” WHO Aassistant director general Dr. Ibrahima Socé Fall added.

WHO emergency committees only exist for COVID-19 and polio. Past emergency committees have been convened for Ebola, H1N1, MERS, yellow fever, and Zika.

The fact that an emergency committee is being convened “tells you that the director is worried,” Dr. Georges Benjamin, executive director of the American Public Health Association, told Fortune on Tuesday.

The WHO has often been accused of reacting too slowly, Benjamin said, adding of Adhanom Ghebreyesu, “I think he’s trying to get his hands around this.”

“When you see something this different, you want to know what you’re missing,” Benjamin said. “You want to lay out a strategy to understand what you don’t know, evaluate what you do know.”

Such a meeting will let health officials from around the globe set an agenda for research and treatment of patients, he said.

“Hopefully we think about how we coordinate this across the world, because it’s clearly a worldwide outbreak.”

As of Tuesday more than 1,600 monkeypox cases had been confirmed in 32 countries, with an additional 1,500 suspected cases pending confirmation, officials said. Seventy-two deaths had been reported in countries where monkeypox is already endemic. No deaths had been reported in countries where it isn’t, but media reports of a monkeypox-related death in Brazil are being explored, officials said.

The WHO does not recommend mass vaccination at this time, officials added.

Testing people with a characteristic rash must increase if the U.S. monkeypox outbreak is to be brought under control, U.S. health officials said Friday, adding that all Americans should familiarize themselves with the disease.

As of Monday the U.S. had seen 65 confirmed cases of monkeypox in 18 states and Washington, D.C., according to CDC data.

While monkeypox presents a low risk to the public, community transmission is possible, and “all Americans should get educated about this disease,” including symptoms and how to prevent it, U.S. health officials said Friday.

As the virus continues to move beyond Africa, where it’s endemic, via an atypical pattern, scientists are rushing to figure out just how it’s spreading.

Monkeypox is usually found in rural African areas where people have close contact with infected rats and squirrels. It is typically transmitted from human to human through close contact, which may include sex and could include contact with personal items like sheets and clothing. Airborne transmission is known to be possible but has yet to be confirmed.

Human-to-human transmission of the smallpox-related virus can occur via “respiratory droplets (and possibly short-range aerosols),” the World Health Organization wrote in a June 4 situation update, in which it cautioned against large gatherings, which may promote transmission.

At a Wednesday press briefing, Rosamund Lewis, WHO’s technical lead on monkeypox, said the risk of aerosol transmission is not fully known, but medical personnel caring for monkeypox patients should wear masks.

In terms of disease transmission, “droplets” and “aerosols” are different. Droplets are larger moisture particles that fall quickly to the ground, like drops of saliva expelled when a person coughs. Aerosols are much smaller particles that can linger in the air. If a virus is spread through aerosols, it is considered airborne.

Last week the U.S. Centers for Disease Control raised its alert level for potential monkeypox transmission among travelers, advising them, among other things, to wear a mask while traveling. On Tuesday the masking advice disappeared from its website. When asked why, the CDC told Fortune it had removed the phrase “because it caused confusion.” The agency did not respond to a request for further elaboration, nor did it respond when asked if there was concern about airborne transmission.