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Australia appears to be experiencing a re-emergence of the infectious disease , formerly called monkeypox.

Some have been recorded so far in 2024, already surpassing the total number recorded for 2023 (26). Victoria has reported , while Queensland saw .

There was previously a significant mpox outbreak in 2022, with a total of across Australia. All cases since 2022 have been in males, most commonly those aged 30 to 39. Mpox cases are on the rise , too.

So what is mpox? And is there a vaccine available? Here’s what to know about this virus.

What is mpox?

Mpox belongs to the orthopoxvirus family, which is also responsible .

Symptoms include , typically starting on the hands, feet and face. The genitals may also be affected. The rash is infectious until the lesions have scabbed over.

There are two clades, or varieties, of mpox: clade I and clade II. of people infected with clade I may die, compared to 1% or less of those infected with clade II.

Traditionally, both clades of mpox have been endemic in countries in central and western Africa, where it transmits from animals to humans, and has occasionally caused human outbreaks.

Mpox outbreaks began occurring outside Africa in 2018, with cases in the United Kingdom, Israel and Singapore in people travelling from Nigeria, which began experiencing outbreaks in 2017.

The 2022 epidemic spread to non-endemic regions such as Europe, the Americas, and Australia, with confirmed globally to date.

These outbreaks were caused by clade IIb, a variant of clade II, with case fatality . Clade IIb is also behind the current cases in Australia.

How does mpox spread?

Recent research indicates both clades of mpox are undergoing , with genetic changes in clade I that may among humans.

These mutations suggest a shift from its historical zoonotic transmission patterns toward .

Mpox spreads between people primarily through close contact with infected lesions or bodily fluids. Sexual transmission accounts for most of clade IIb’s spread, especially among like gay, bisexual, and other men who have sex with men.

The pattern of spread appears different for the two clades. Like smallpox, mpox is a respiratory virus and has been found , so respiratory transmission is possible.

Clade I is causing large epidemics in the (DRC), with more than since 2023.

The estimated , with and close to 90% of deaths in children under 15.

This suggests respiratory and close-contact transmission are the primary modes of spread in DRC. However, of clade I has also been reported.

Vaccination is our best bet

The primary strategy for preventing further outbreaks of mpox in Australia is vaccination. The recommended shot is the , which was developed as a smallpox vaccine.

Older smallpox vaccines are made from a live virus called vaccinia, a related orthopoxvirus that protects against smallpox and mpox. The older vaccines have fully replicating vaccinia virus in them, which can be risky for people with weakened immune systems. The JYNNEOS vaccine is modified so the vaccinia virus doesn’t replicate in the body and is safer for people with conditions such as HIV.

For full protection, two doses are required at least 28 days apart. Two doses given before exposure to the virus is in preventing mpox and for at least a couple of years.

Cases in people who are vaccinated, but these infections are typically milder.

The vaccine is also effective to the virus, but less so than if it’s given beforehand.

Who should get vaccinated?

Australian recommend vaccination in gay, bisexual, and other men who have sex with men. They also recommend vaccination for sex workers, and people with HIV who may be at risk of exposure to mpox.

Health-care workers who treat or are likely to treat patients with mpox are advised to consider having the vaccine.

Post-exposure vaccination is recommended for people who public health authorities classify as having had a high-risk mpox contact in the previous 14 days.

Australia’s approach to the 2022 mpox outbreak involved ensuring early access to vaccination and working closely with LGBTQ+ community and health organisations. These organisations of mpox symptoms, modes of transmission, and vaccination.

In 2023, 48% of gay and bisexual men in and reported having received at least one dose of mpox vaccine. Rapid uptake of vaccines may have contributed to low rates of mpox in Australia.

Future focus

It appears mpox has become established as a sexually transmitted infection in gay, bisexual, and other men who have sex with men. Achieving and maintaining high rates of vaccination in this group will be crucial in long-term prevention efforts.

Ongoing surveillance is also important, while contact tracing will help minimise the size of any clusters, facilitating post-exposure vaccination where warranted. In Australia, state and territory health departments have extensive experience in contact tracing and work with affected communities.

Australia has so far been successful in avoiding a major epidemic, including in early 2023 when brought thousands of gay men from around the world to Sydney.

In the next few years, unequal access to vaccination around the world will likely mean continued introductions of mpox from settings with lower vaccination rates. Ensuring is vital to global and local disease control.

A global approach to controlling mpox is essential, as infections in one country can spread rapidly internationally, as the 2022 epidemic showed.

C Raina MacIntyre receives funding from NHMRC and MRFF. She has been on advisory boards for Bavarian Nordic and received funding for a smallpox workshop she conducted in 2019 from Emergent Biosolutions, Bavarian Nordic, Siga technologies and Meridien Medical. She is on the WHO SAGE Smallpox and Monkey Pox Ad Hoc Advisory Group.

Andrew Grulich and Mo Hammoud do not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and have disclosed no relevant affiliations beyond their academic appointment.