This week, the World Health Organisation declared a global emergency for the infectious disease mpox, formerly known as monkeypox.

In central Africa more than 500 people have died – most of those deaths are in children under the age of 15 – and many thousands are infected.

It’s important to note that the variety of mpox in Australia – where infections have become more frequent – is far less lethal than that plaguing central Africa.

And we’ll get back to that.

Australian situation

In Australia, there has been a significant spike of mpox cases over the past two months.

Indeed, there have been many more cases recorded in those two months than were recorded in the whole of 2022, when the virus first arrived in Australia.

In June, there were about 40 or so cases of mpox in Australia.

As of Thursday, according to the National Notifiable Diseases Surveillance System, Australia has recorded 241 cases for 2024.

In 2022 there were 144 cases recorded for the year – a situation that epidemiologists described as a serious outbreak.

Of the new cases, one of them was a female, which is unusual.

As a Conversation piece in June noted: “It appears mpox has become established as a sexually transmitted infection in gay, bisexual, and other men who have sex with men.”

Two of the cases were in the 15 to 19 age grouping. One of them was in the 85-plus grouping.

What is mpox?

Mpox is a completely different virus to SARS-CoV-2.

It’s a less-deadly relative of the smallpox virus.

However, while smallpox was confined to humans, monkeypox occurs in animals, such as monkeys and rodents – and can be spread to a person via a bite.

The virus is spread to other people through direct contact with body fluids or sores on the body of someone who has mpox – or with direct contact with materials that have touched body fluids or sores, such as clothing or linens.

It may also spread through respiratory secretions when people have close, face-to-face contact.

However, mpox is “not known to linger in the air and is not transmitted during short periods of shared airspace”.

According to the WHO, symptoms of mpox typically include a fever, intense headache, muscle aches, back pain, low energy, swollen lymph nodes and a skin rash or lesions.

Symptoms typically last between two to four weeks and go away on their own without treatment.

The different varieties

According to the June Conversation piece, co-authored by Raina MacIntyre, Professor of Global Biosecurity, Kirby Institute, UNSW:

There are two clades, or varieties, of mpox: Clade I and clade II.

Up to 10 per cent of people infected with clade I may die. This is the variety that’s causing havoc in central Africa.

Death rate of clade II is one per cent or less of those infected with clade II.

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

Mpox outbreaks began occurring outside Africa in 2018.

The 2022 epidemic spread to non-endemic regions such as Europe, the Americas and Australia, with more than 97,000 cases confirmed globally to date.

These outbreaks were caused by clade IIb, a variant of clade II, with case fatality below one per cent. Clade IIb is also behind cases in Australia.

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

These mutations suggest a shift from its historical zoonotic transmission patterns toward sustained human-to-human spread.

Vaccine highly effective

The primary strategy for preventing further outbreaks of mpox in Australia is vaccination.

The recommended shot is the JYNNEOS vaccine, which was developed as a smallpox vaccine.

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 84 per cent effective in preventing mpox and protection is believed to last for at least a couple of years.

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

 Vaccination guidelines

Australian guidelines 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.

Healthcare 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.

Cases of mpox can occur in fully vaccinated or partially vaccinated individuals. But these cases tend to be milder.