Monkeypox outbreak: Some older Kiwi globetrotters may already be immune

A local monkeypox case is likely but a big outbreak is not, and some older people might already have immunity, a public health expert says.

Monkeypox has been spreading in North America, Europe and Australia.

"It's quite likely we will see an imported case at some stage," Professor Michael Baker said.

He said the disease had now been recorded in at least 18 countries where it was not endemic, and case numbers earlier today numbered 237 outside Africa.

"We expect those numbers to grow, just because it's got a long incubation period," the University of Otago epidemiologist added.

Incubation - from infection to symptoms - usually lasted one week to a fortnight but could be as long as three weeks.

The right arm and torso of a patient, whose skin displayed a number of lesions due to what had been an active case of monkeypox in the 1990s. Photo / CDC via AP

Monkeypox was not a highly-transmissible disease, and required close contact to spread, Baker said.

A chance event appeared to have brought monkeypox out of Africa, and there was evidence it was spreading mostly between men who had sex with men, he said.

The virus had two clades and Baker understood the West African clade had arrived in Europe.

He said that clade had a fatality rate of about 1 per cent, compared to the Congo Basin version's roughly 10 per cent.

"There is a very low risk of causing deaths but it can be serious, and children in particular can get a serious illness."

The World Health Organisation has said vaccination against smallpox was shown to be protective against monkeypox.

"A lot of older New Zealanders would have had smallpox vaccinations for travel overseas," Baker said.

Smallpox was eradicated in 1980 but many other countries had mass vaccination programmes for smallpox in the past, Baker added.

New Zealand should review its smallpox vaccine stockpile, Baker said.

The so-called third generation smallpox vaccine was still used as a bioterrorism countermeasure, according to Science Direct.

It was also used as a recombinant vaccine vector for other infectious diseases, such as viral haemorrhagic fevers.

One vaccine and one specific treatment were approved for monkeypox.

"You don't have to vaccinate the whole population," Baker added.

University of Otago epidemiologist Professor Michael Baker says contact tracing and isolation would probably be used if monkeypox arrived in New Zealand. Photo / Supplied

But he said good case identification and contact tracing would help prevent any outbreak growing.

Baker said New Zealanders need not worry about a major monkeypox outbreak but health officials should be conducting risk assessments and trying to understand the virus.

Some surveillance at airports could be useful, he said.

A person arriving from a country with monkeypox cases and sporting a rash resembling chicken pox would probably have to be isolated and tested.

The US Centres for Disease Control and Prevention said in humans, monkeypox symptoms were similar to but milder than smallpox symptoms.

Infected people might have fevers, headaches, muscle aches, and exhaustion.

Scotland's first monkeypox patient was in hospital yesterday, the BBC reported.

According to US News & World Report, most current reported cases in non-endemic countries were in Spain, Portugal and the United Kingdom.

"We certainly have to be prepared for the scenario because it has been in other Western countries," Associate Minister of Health Ayesha Verrall said on Monday.

Monkeypox lesions were distinctive but the disease could incubate undetected at first.

"There is an antiviral developed but most monkeypox cases in the world recover without treatment, to be honest," Verrall told the Herald.