Australia has recorded its second official case of monkeypox with NSW confirming its first case after Victoria.
NSW Health had flagged the case of a man in his 40s who returned recently from Europe and confirmed the infection after further tests on Friday evening.
The man, and a household contacted are isolating at home, after he had developed a mild illness several days after arriving in NSW.
The Victorian health department confirmed a case of the rare tropical illness on Friday afternoon in a returned traveller from the United Kingdom.
The man in his 30s developed mild symptoms before arriving in Melbourne on 16 May and he sought medical attention almost immediately.
A general practitioner referred him for testing, which came back positive, and he was placed in isolation at The Alfred hospital on Thursday.
His close contacts may need to quarantine and some will be offered the smallpox vaccine.
Contact tracing is also underway for passengers seated near the man on flight EY10 from London to Abu Dhabi on 15 May, and flight EY462 from Abu Dhabi to Melbourne on 16 May.
Oval-shaped monkeypox virions (left) and spherical immature virions (right). Health authorities say monkeypox is not easily spread between people. Credit: AP
They are being asked to monitor for flu-like symptoms and only isolate if they develop.
Australia joins Italy, Sweden, the United Kingdom, Spain, Portugal and the United States as nations dealing with outbreaks.
Monkeypox occurs mainly in central and western Africa, often close to tropical rainforests, and is considered endemic in the Democratic Republic of Congo where it was discovered in humans in 1970.
The illness can be transmitted from person to person through air droplets, close bodily contact or sharing contaminated linens or objects.
Four African countries - Cameroon, Central African Republic, Democratic Republic of Congo and Nigeria - have reported cases of monkeypox in 2022.
NSW Chief Health Officer Kerry Chant said monkeypox was a rare virus and did not spread easily between people.
NSW Chief Health Officer Dr Kerry Chant says monkeypox is not easily transmissible between people. Source: AAP / BIANCA DE MARCHI/AAPIMAGE
She said a large number of overseas cases were among gay and bisexual men and urged those men to "be aware of any unusual rashes or lesions" and to contact their GP or a sexual health clinic if concerned.
She said people should be "particularly vigilant" if they had returned to Australia after attending large parties or sex-on-premises venues overseas.
"The infection is usually a mild illness and most people recover within a few weeks," she said.
NSW-based sexual health organisation ACON urged gay, bisexual and men who have sex with men to remain vigilant and follow health advice.
"It's important we remember that viruses do not discriminate," said ACON CEO Nicholas Parkhill on Friday.
The World Health Organisation also called for vigorous contact tracing around the spate of cases.
Prime Minister Scott Morrison said state health authorities are closely monitoring the situation and he'd been advised the virus was less contagious than COVID-19.
"We should be taking this seriously (but) at the same time I would say that no one should be alarmed at this point," Mr Morrison told reporters in Perth.