A rare virus called monkeypox has made its way to the U.S. with a case in Massachusetts and now a possible case in New York City.

City health officials say they are conducting preliminary tests.

Doctors say monkeypox looks similar to smallpox and got its namesake after it was discovered in 1958 during an outbreak among monkey colonies. They say the virus behaves differently than COVID-19, adding there is no need to panic.

"This is not the time to be concerned, at least not yet," says Dr. Robert Amler from NY Medical College. "The monkeypox virus is contagious but it does not spread anywhere nearly as fast."

Amler, who is also a former Centers for Disease Control and Prevention physician and epidemiologist, says the disease is not something people expect in the U.S.

According to the CDC, monkeypox is transmitted through broken skin, the respiratory tract or through mucous membranes, body fluids and animal bites or scratches. Symptoms include flu-like symptoms, a rash and swollen lymph nodes. Officials say the illness lasts two to four weeks.

"Like all infections people should be aware of not being exposed to other people who seem to be sick, because whatever virus they have, you don't want," says Amler.

There is already a vaccine for monkeypox, but it is hard to find because the disease is rare in the U.S. Amler says if the disease started to spread, the government would push for mass production of the vaccine.