Monkey pox has mutated – even its name – and is creating new challenges for public health watchdogs.
By Eric Martin
Only two years ago, monkey pox was a medical curiosity for Australian doctors, but fast-forward to 2024 and WA Health is asking GPs and people at risk of contracting the virus to be vigilant after two locally acquired cases were reported in WA.
While the local cases – which are still being investigated – are the milder Clade 2 strain of mpox and not connected to the more severe Clade 1b strain that is spreading in Western Africa, experts strongly recommend that those at risk still be vaccinated against the previous strain, as Australian cases are expected to surpass previous years.
More than 17,000 cases and 5037 deaths have been detected in the Democratic Republic of Congo and the recent change in transmission dynamics in Africa have alarmed global health officials. Less than 24 hours after the World Health Organization declared the new strain of mpox virus and a global public health emergency, the first case in Europe was confirmed in Sweden.
Mpox can be spread through skin-to-skin contact, including during sex, and contact with contaminated items such as bedding and towels, with a lower risk of infection from breathing in droplets from coughs and sneezes.
Symptoms usually start within five days to three weeks of exposure to the virus and can include a rash that can look like bumps, pimples or sores, which later develop into fluid-filled lesions, pustules or ulcers. Some people also exhibit fever, headaches, muscle aches, backache or enlarged lymph glands.
WA Health’s Communicable Disease Control Director, Dr Paul Armstrong said people with the Clade 2 strain usually experienced a milder illness which could last for two to four weeks. He urged high-risk groups in the community to be alert for symptoms and seek testing promptly.
“Mpox infections have been increasing in Australia over the past few months – particularly among sexually active men who have sex with men and through higher risk activities such as casual sex and multiple partners,” Dr Armstrong said.
“The numbers seen in Australia in 2024 have all been Clade 2b. Only a few people experience more severe illness, and many cases are resolved without specific treatment. This is the same pattern we saw in 2022 with the global spread of mpox at that time.
“What has been challenging this year is the ability to identify sexual partners of mpox cases easily as many people may not know the contact details of their partners, which is why we are encouraging people at risk to exchange those details with each other so they can be contacted if someone is later identified to have mpox.
“The change in behaviours in men who have sex with men, as well as the roll out of the mpox vaccine helped control the 2022 outbreak. If people have any symptoms suggestive of mpox – even if they are mild and they have had the mpox vaccine – they should contact their GP or sexual health service for an appointment.
“And importantly, wear a mask, call ahead and cover up any rashes, bumps or pimple-like sores.”
Dr Armstrong said some of the most effective ways to prevent the spread of mpox were to avoid sex if there were any signs of sores or blisters, limiting sexual partners, and keeping contact details of new partners to help with contact tracing if needed.
“Condoms offer some protection, but only protect the area of skin covered as sores can be on and around other parts of the genitals and body,” he said.
“Now that we are seeing locally acquired cases of mpox in WA, it’s important to raise awareness of this virus and encourage people at risk to get vaccinated. Vaccination plays an important role in reducing the severity of illness and preventing spread among those at highest risk of contracting mpox, which is important to protect people who may be vulnerable to severe infections.”
The JYNNEOS® mpox vaccine is free for those considered to be at higher risk including sexually active men who have sex with men (cis and trans) and their sexual partners, as well as sex workers and their sexual partners.
Two doses at least 28 days apart are required for optimal protection, though at this stage, given the emergence of the new strain, the mpox vaccine is not being considered as a travel vaccination for people travelling to Africa unless they are otherwise eligible.
Dr Armstrong explained that while the Clade 2b virus, like all viruses, constantly mutated during replication and spread, it had not mutated to the point where it had significantly changed its transmissibility or ability to cause significant disease.
“We know this is the case as we can see genomic differences in the cases detected in Australia in 2024,” he said.
“What has happened recently in Central and West Africa, with the emergence of Clade 1b, is the mutation of Clade 1 that has created a new strain or lineage of the disease. The genomic analyses show that it is distinctly divergent from previously circulating strains in the Democratic Republic of Congo.”
He suggested that those interested should read the recently published article in Nature Medicine, ‘Sustained human outbreak of a new MPXV clade I lineage in eastern Democratic Republic of Congo.’
“We know that clade 1b has also been seen in groups other than men who have sex with men in Central and West Africa, such as children and women, but we don’t yet know if this will be the case if it spreads and sustains transmission outside Africa.
“The current vaccines are thought to be effective against all strains of mpox and were vaccines initially developed against smallpox. Smallpox and monkeypox viruses belong to the same family – the orthopoxvirus family – so the smallpox vaccine also protects against mpox.
“At the moment, we don’t know fully understand if the vaccines will be as effective against the Clade 1b strain, as it was against the strain we are seeing in Australia – the Clade 2b strain though studies have reported that the vaccine is as high as 80% (one dose) or 88% (2 dose) effective at preventing the disease in at-risk people.”
Currently, the vaccine is only considered necessary for those at higher risk due to sexual activity, and Dr Armstrong noted it was unlikely that Australia would extend the provision for people working in primary healthcare settings.
“While healthcare workers who work in clinics or practices with a high throughput of patients with sexual health complaints may be eligible for the vaccine, it is not currently recommended for most healthcare workers,” he said.
“There have not been many secondary cases in healthcare workers anywhere in the world, so the risk in healthcare settings has been deemed low. Additionally, appropriate infection prevention and control measures including personal protective equipment will protect healthcare workers from mpox.
“However, ultimately that would depend on the epidemiology of mpox.”
While there are no specific comorbidities or genetic predispositions that make certain people more susceptible to mpox infection than others, Dr Armstrong pointed out that those most at risk of severe disease included immunocompromised people, especially those living with poorly controlled HIV infection.
“In the context of spread outside of men who have sex with men, children and pregnant women may also be at greater risk of severe mpox disease – and we know this is the case with Clade 1 mpox infections in children in Central and West Africa,” Dr Armstrong said.
“This does not necessarily mean that they are engaging in sexual activity, as the most likely course of transmission in these contexts are through contact with sores and contaminated clothing or bedding.
“Mpox is still predominately seen in the men who have sex with men cohort so Australian GPs should consider relevant screening for those presenting with clinically compatible symptoms such as a rash or pox-like lesion.
“Patients may also present with proctitis, and a travel history should be taken if mpox is suspected to help ascertain the risk of Clade 1
or 2I infection.”
WA Health has developed a one-page guide for GPs to help assessment, testing and diagnosis, and infection prevention control recommendations and notification requirements. It can be found at www.health.wa.gov.au/~/media/Corp/Documents/Health-for/Infectious-disease/Monkeypox/Monkeypox-quick-guide-for-clinicians.pdf.
“The Department continues to monitor the situation closely, both nationally and internationally, and will provide additional advice to GPs if the situation changes,” Dr Armstrong said.
“Specifically, the Communicable Disease Control Directorate releases clinician alerts which provide important updates on communicable disease risks. GPs can subscribe to the disease alert mailing list and receive key updates to their inbox, and other resources include the Australian Society for HIV, Viral Hepatitis and Sexual Health Medicine (ASHM) decision making in mpox quick reference tool – found on ASHM’s webpage, as well as the STI guidelines.”