CHICAGO (NewsNation) — As more confirmed and suspected monkeypox cases spread worldwide, health officials suspect the virus is spreading through raves and sexual contact.

The Centers for Disease Control and Prevention is investigating a patient diagnosed with monkeypox in Boston who had contact with more than 200 people. Health leaders are also investigating two suspected but not confirmed cases in Utah.

More than 100 monkeypox diagnoses worldwide, and that number is climbing.

“There’s about three to six percent chance of becoming deadly, but this really seems much more mild, no cases of people becoming seriously ill or dying from it,” said Dr. Kristin Englund, an infectious disease staff physician at Cleveland Clinic.

There is no proven treatment for the virus, but there is a vaccine with evidence to be effective. The illness is consistent with the smallpox family but not nearly as dangerous and deadly.

“I don’t think people need running out looking for the vaccine for this. The vaccine we actually have is the smallpox vaccine because they are in the same family,” Englund said.

U.S. health leaders are preparing a stockpile of the vaccine for most at-risk patients. Incubation of monkeypox can take about 7 to 14 days and symptoms can last a few weeks, starting with a headache, tiredness, and muscle aches to a rash and then legions and scabs on the skin, mostly seen on the face, arms, and genital areas. “That is when people are very infectious during all of those stages and people remain infectious until the scabs fall off,” Englund said.

Doctors say monkeypox is not as contagious as COVID-19; it spreads through hours of skin-to-skin contact and enters through broken skin, eyes, nose or mouth.      

It can also spread through animals and materials that have been contaminated. However, officials say it’s not considered a sexually transmitted disease.

“This is a disease that has been around and been available to humans for 50 years, and we’ve certainly not seen huge outbreaks of monkeypox,” said Englund

Health leaders said most positive cases in the last three weeks had been seen in Europe and North Africa linked to pride raves. The World Health Organization says most cases have been linked to sexual contact among men.

Some positive cases have even been seen in roommates.