Four cases of mpox - formerly known as monkeypox - were recorded in Hunter New England last month, health data shows.
This was also the total number of cases recorded in the district this year, following one last year and one the year before.
University of Newcastle Professor Nathan Bartlett said mpox was "a relative of the now eradicated human pathogen variola virus - the causative agent of smallpox".
"Mpox is not as transmissible as variola virus. Mpox relies on close human to human contact," Professor Bartlett said.
He said the spread of mpox was troubling, but vaccines against viruses like variola and mpox were "highly effective".
"Indeed, smallpox is the only viral disease to be completely eradicated by vaccination.
"So with a co-ordinated international response - surveillance, education, vaccination - control of this outbreak and future outbreaks is achievable."
Professor Bartlett, of Hunter Medical Research Institute, said "right now the biggest concern is Africa - the Democratic Republic of Congo and surrounding countries".
He said people who go to areas where outbreaks were occurring could then bring the disease back to Australia.
"If you're travelling to those places, you should take precautions, be aware of the symptoms and respond appropriately," he said.
"If the virus starts circulating in our community, that takes it to another order of magnitude.
"That's the important thing to discriminate between - people coming back with the virus versus an outbreak, which means it's actually spreading from person to person within our community.
"If there are enough people in our community who are bringing the virus in, then there is the potential for it to start spreading internally."
He said people at high risk of exposure and infection should be aware of the symptoms.
"If you start to get a rash and feel unwell and know you've been in contact with affected individuals in a high-risk area, you should really be going to get checked out."
NSW Health said last Friday that there had been 93 detections of mpox in the state since June 1.
"Before June 1, only one case had been detected in NSW in 2024," it said.
It said this increase in infections was mostly affecting "men who have sex with men".
Since 2022, there has been a global outbreak of mpox, with more than 97,000 reported cases in many countries outside Africa, including Australia.
NSW Health's Jeremy McAnulty said there had been more than 15,000 cases of mpox reported in central Africa this year.
Many of these cases were "due to a new strain (clade 1b) of the virus".
"However, this strain has not been detected in Australia," Dr McAnulty said.
"Mpox spreads through close skin-to-skin contact, including sexual contact."
He said it often starts with small pimple-like skin lesions, "particularly in areas that are hard to see such as the genitals, anus or buttock".
"Some people experience mild fever, headache, fatigue, or swollen lymph nodes and mouth ulcers or rectal pain.
"Mpox can spread to others until the lesions resolve."
Call the Sexual Health Infolink on 1800 451 624 for vaccine booking support.
Call the Translating and Interpreting Service on 13 14 50 for free help in your language.
