As of Friday, eleven countries were investigating possible monkeypox cases, including the United States, where a second possible case was reported in New York City Thursday night.

According to the World Health Organization, the disease is normally restricted to parts of west and central Africa.

On Wednesday, the first case in the United States was reported in Massachusetts.

Canada confirmed two monkeypox cases on Thursday and is investigating another 15, officials said. Officials in eight European countries have suspected or confirmed cases: the United Kingdom, Spain, Portugal, Italy, Sweden, Belgium, France, and Germany.

In Australia, two cases have also been reported.

According to the World Health Organization, no single source of infection has been identified. Monkeypox is not a monkey disease, but rather one that affects small rodents in central and western Africa. The rodents infect monkeys, and both can transmit the disease to humans.

While most cases of the disease are caused by contact with wild animals rather than human-to-human contact, health officials are looking into how the new wave of cases is spreading.

Some of the cases appear to have spread between sexual partners, and all of the reported cases appear to be in men thus far.

“The majority of those cases are men between the ages of 35 and 50 who have had sexual relationships with other men,” Dr. Mylène Drouin, Montreal’s public health director, said at a news conference on Thursday. “The clinical presentation is primarily ulceration of the oral and genital parts, which is painful, with a fever, sweating, and headaches preceding the eruption.”

Monkeypox, a much less dangerous cousin of smallpox, is not a sexually transmitted disease, according to experts.

The majority of patients appear to have ulcerative lesions, rash, and swollen lymph nodes, which are frequently accompanied by fever, chills, headache, muscle pain, and tiredness. Anyone who is experiencing these symptoms should contact their doctor.

Many possible cases are misidentified as monkeypox because the disease can be confused with other infections and skin rashes.

In fact, it can be difficult to distinguish from chickenpox. “You get fevers, swollen lymph nodes, and small little fluid blisters all over your body,” explained Dr. Seth Blumberg, an infectious disease specialist at the University of California, San Francisco.

There is no need for public concern because monkeypox is not highly contagious.

“This isn’t COVID once more.” “This isn’t Wuhan, China in 2019.” said Blumberg.

According to Dr. Aaron Glatt, chief of infectious diseases at Mount Sinai South Nassau Hospital in Hewlett, NY, anyone who hasn’t been in very close physical proximity to someone infected with monkeypox is unlikely to be at risk.

Prior to this, according to a paper published in the journal “PLOS: Neglected Tropical Diseases” in February, all but one case of monkeypox outside of Africa was the result of either confirmed or suspected animal-to-human transmission.

The only case of human-to-human transmission occurred between a health care worker in the United Kingdom and a patient there.

It will take careful public health investigation to determine how or if the latest cases are linked.

Monkeypox is part of a virus family that includes smallpox, one of the most lethal diseases to ever infect humans, killing roughly one in every three people who contracted it before it was eradicated in 1980, considered one of the greatest public health achievements of all time.

According to Glatt, the death rate for monkeypox in areas with high-quality medical care is well below 1% of cases.

The last major outbreak in the United States occurred in 2003, when small mammals shipped from Ghana to Texas tested positive for monkeypox, including rope squirrels, tree squirrels, African giant pouched rats, brush-tailed porcupines, dormice, and striped mice.

Some of the infected animals were then transported to the facilities of an animal vendor in Illinois, where they infected prairie dogs kept in nearby cages. The prairie dogs were later sold as pets, resulting in the outbreak.

Monkeypox outbreaks are thought to be on the rise in part because, after the smallpox virus was eradicated in 1980, widespread vaccination against the disease ceased. Vaccination against smallpox protects against monkeypox, said Rimoin.