More than 100 confirmed or suspected cases of monkeypox have been reported in 12 countries, including the US

More cases of a rare disease have been reported worldwide, including in the United States -- where one health official said he expects more cases in the days ahead.

As of Saturday, 92 confirmed cases and 28 suspected cases of monkeypox were under investigation in 12 countries, the World Health Organization said in a news release.

Confirmed cases have been identified in Australia, Belgium, Canada, France, Germany, Italy, the Netherlands, Portugal, Spain, Sweden, the United Kingdom and the United States -- which had between one and five confirmed monkeypox cases as of Saturday, the WHO said.

"The situation is evolving and WHO expects there will be more cases of monkeypox identified as surveillance expands in non-endemic countries," the news release said.

it's spread very differently than SARS-CoV-2" -- the virus that causes Covid-19, Jha told ABC's Martha Raddatz on Sunday.

"It's not as contagious as Covid. So I am confident we're going to be able to keep our arms around it," Jha said. "But we'll track it very closely and use the tools we have to make sure we can continue to prevent further spread and take care of the people who get infected."

Health experts say close contact with an infected person is required to spread the monkeypox virus.

Infection can develop after exposure to "broken skin, mucous membranes, respiratory droplets, infected body fluids or even contact with contaminated linen," according to Neil Mabbott, personal chair in immunopathology at the veterinary school of the University of Edinburgh in Scotland.

Though experts say monkeypox is not as contagious as Covid-19, President Joe Biden said everyone should be concerned about the spread of monkeypox -- even as scientists work to learn more about the recent spread.

CNN previously reported that the US Centers for Disease Control and Prevention is evaluating whether a smallpox vaccine should be offered to health care workers treating monkeypox patients and other people who may be at "high risk" for exposure to monkeypox.

The variola virus that causes smallpox and the monkeypox virus are somewhat related, as they are both members of the Orthopoxvirus genus -- belonging to the scientific family of "pox" viruses. Therefore, some of the same vaccines given to prevent smallpox have also been shown to prevent monkeypox.

Initial monkeypox symptoms are typically flu-like, such as fever, chills, exhaustion, headache and muscle weakness.