The most recent case of mpox in New Zealand has been linked to the Winter Pride Festival in Queenstown. File picture. Photo: SERGII IAREMENKO/SCIENCE PHOTO L / SIA / Science Photo Library via AFP
Health professionals are continuing to investigate after a case of mpox was linked to the recent Winter Pride Festival in Queenstown.
National Public Health Service clinical director Dr Susan Jack said a number of people who attended the event, came into contact with people who later tested positive for mpox overseas.
Te Whatu Ora said its response to the outbreak includes contact tracing and support, testing and treatment, prevention activities and mpox consultations where appropriate.
Five cases of mpox have been detected in New Zealand this year, while the World Health Organisation has declared an outbreak in Africa of one strain of the virus, a public health emergency.
But health experts say the mpox outbreak in New Zealand is manageable - the virus spreads differently in developed countries and there have been no cases of most severe strains detected on our shores.
What is mpox?
The Centers for Disease Control and Prevention says mpox is a zoonotic disease caused by infection with a virus. It is an infectious illness that can be transmitted between animals and humans.
It was first discovered in 1958 in colonies of crab-eating macaques that were being kept for research. Despite originally being named "monkeypox", the source of the disease remains unknown although scientists suspect African rodents and non-human primates, like monkeys, might harbour the virus and infect people.
It is now endemic in parts of central and west Africa. The first human case was recorded in 1970, in what is now the Democratic Republic of the Congo.
In 2022, mpox spread throughout the world. Before that cases outside Africa were rare and usually linked to travel or to animals being imported from regions where mpox is endemic.
It is transmitted through close physical contact with an infected person or animal, and through contaminated materials (such as clothing and linen).
Is there a cause for concern in New Zealand?
In New Zealand, there have been 54 cases since the disease became notifiable in June 2022, with five cases confirmed so far this year - the most recent linked to the Queenstown Winter Pride Festival.
These cases have all been a strain called clade II, the type that caused the global outbreak in 2022. Infections from this strain are generally less severe.
Last month, the World Health Organisation's director general, Dr Tedros Adhanom Ghebreyesus, declared the mpox outbreak a public health emergency of international concern, in part due to the rapid spread of a new virus strain in the Democratic Republic of the Congo, called clade 1b. Cases of the virus have been recently detected in Burundi, Kenya, Rwanda and Uganda, where it had not previously been seen.
University of Canterbury's professor Michael Plank said the different strains of mpox were currently spreading globally with different characteristics.
He said the increase in global transmission of mpox was likely due to the fact the smallpox vaccine provided cross-immunity against mpox, but it was discontinued after the disease was eradicated in 1980, so the number of people without immunity had been increasing since then.
All cases detected in New Zealand so far were clade II.
Plank said it was important that samples from new cases were genomically sequenced so if clade Ib did arrive in New Zealand, the health system could respond appropriately.
"There have been some reports that clade Ib has a higher fatality rate. However, this is difficult to pinpoint because the number of undetected cases is unknown, and it is difficult to disentangle the impacts of the different clades and subclades that are spreading concurrently in Africa."
Plank said New Zealand also needed to play its part in getting vaccines to African countries that were struggling to control outbreaks and where vaccines were in short supply.
Who is most at risk and what are the symptoms?
An infectious diseases specialist says the spread of mpox in New Zealand can be limited - if people are vigilant and follow public health measures.
University of Auckland professor Mark Thomas said in developed countries - the virus was mainly spread through sexual contact and can be brought under control by vaccination.
"Mpox has become established as a new sexually transmitted infection in many countries, including New Zealand, and is likely to continue to cause intermittent outbreaks in those countries where sufficient numbers of high risk MSM [men who have sex with men] remain unvaccinated.
"The disease lasts about two weeks, and may cause significant discomfort at the site of initial infection, but is very rarely fatal."
He said it could take a week, or even 10 days for someone to start developing symptoms. This is referred to as the incubation period.
The symptoms are similar to a flu-like illness; fever, aches, and pains, feeling tired, lack of appetite.
After these symptoms appear, a person will start noticing small lesions. These start as small raised red bumps, develop into a blister, then scab over and fall off. That process usually takes up to two weeks.
The virus is transmitted through close skin to skin contact with someone who is infected, there is a low risk of this occurring during the incubation period, but a person is most infectious once they've developed the skin lesions.
"I'm hoping that it won't spread widely through the population of men who have sex with men in New Zealand, because I think it's likely that with one case identified, and hopefully not too many more identified that those people will not be exposing other people to their skin while they are infectious," Thomas said.
Health professionals say vaccines are the best way to proactively prevent against contracting mpox.
But the vaccine is currently unapproved in New Zealand, and can only be made available to patients by a medical practitioner through section 29 of the Medicines Act 1981.
In Aotearoa New Zealand, gay, bisexual and other men who have sex with men (MSM) have the highest risk of transmitting mpox.
Auckland University researcher and associate professor of social and community health Peter Saxton believes this was due to the community's close sexual networks.
"We are a globally interconnected community and vaccine coverage among New Zealand men who have sex with men remains woefully low."
Trans and non-binary people who have sex with MSM are also considered high risk, and are eligible for free vaccinations through their GP, as well as anyone who is a close contact of someone who has been infected with mpox.
How do we deal with an outbreak?
Burnett Foundation Aotearoa chief executive Joe Rich said not everybody who attended the Winter Pride event needed to be concerned, but if someone was experiencing symptoms, or had been notified as a contact, they should refrain from sex and get tested at a local sexual health clinic.
Public Health professor Michael Baker said the mpox epidemic was manageable and eliminating it in New Zealand was a realistic goal.
"It is important to remember that mpox has continued to circulate widely since the epidemic in 2022-23. Even though that epidemic peaked in August 2022, this infection continues to spread in many counties with more than 100,000 cases reported to date."
He said basic public health and social measures such as case diagnosis, isolation, contact tracing and quarantine of contacts were highly effective at limiting the spread of the virus.
While all the cases in New Zealand had been clade II, he said we were likely to see clade I cases in the future.