(NewsNation) — President Joe Biden said “everyone should be concerned” about the spread of monkeypox as the World Health Organization answered public questions about the spread of the virus.

“It is a concern in that if it were to spread it would be consequential,” Biden said in his first public comments on the disease. “They haven’t told me the level of exposure yet but it is something that everybody should be concerned about.” He added that work was underway to determine what vaccine might be effective.

However, Biden clarified his comments later, saying, “I just don’t think it rises to the level of the kind of concern that existed with COVID-19.”

Monkeypox is rarely identified outside Africa, but as of Friday, there were 80 confirmed cases worldwide, including at least two in the United States, and another 50 suspected ones.

Although the disease belongs to the same virus family as smallpox, its symptoms are milder. People usually recover within two to four weeks without needing to be hospitalized, but the disease occasionally is deadly.

The WHO does not have evidence that the monkeypox virus has mutated, a senior executive at the U.N. agency said on Monday, noting the infectious disease that is endemic in west and central Africa has tended not to change.

A leading adviser to the World Health Organization described the unprecedented outbreak of the rare disease in developed countries as “a random event” that might be explained by risky sexual behavior at two recent mass events in Europe.

In an interview with The Associated Press, Dr. David Heymann, who formerly headed WHO’s emergencies department, said the leading theory to explain the spread of the disease was sexual transmission among gay and bisexual men at two raves held in Spain and Belgium. Monkeypox has not previously triggered widespread outbreaks beyond Africa, where it is endemic in animals.

“We know monkeypox can spread when there is close contact with the lesions of someone who is infected, and it looks like sexual contact has now amplified that transmission,” said Heymann.

That marks a significant departure from the disease’s typical pattern of spread in central and western Africa, where people are mainly infected by animals like wild rodents and primates and outbreaks have not spilled across borders.

To date, WHO has recorded more than 90 cases of monkeypox in a dozen countries.

Jake Sullivan, Biden’s national security adviser, told reporters aboard the flight to Tokyo that the United States has a supply of “vaccine that is relevant to treating monkeypox.”

“We have vaccine available to be deployed for that purpose,” he said. Sullivan said Biden was getting regular updates on the outbreak.

The Associated Press contributed to this report.

This story is developing. Refresh for updates.