Whakaari / White Island eruption: Victims still fighting for their lives one month on

Families of victims of the Whakaari / White Island eruption are preparing to mark a month since the devastating blast that took the lives of 19 people.

Twenty-five others are still in hospital here and in Australia, with some still requiring round the clock care and fighting for their lives.

The island itself is still off-limits; scientists say its peak activity may have come and gone with the eruption, or this might be the start of something bigger.

The brother of missing tour guide Hayden Marshall-Inman is hopeful his body will be found.

But the way Mark Inman sees it is that Hayden is now the guardian of Whakaari/White Island. Living on the East Coast in Ōhope, he's not far from the island his brother loved so much and visited more than 1000 times.

"We look at White Island every single day. We wake up seeing White Island. I mean, what better monument to have. It's pretty special," Inman said.

Inman hasn't been told of any clues of Hayden's whereabouts since police suspended the search for his body, and that of Australian teenager Winona Langford, on Christmas Eve.

He said the focus was now on those in hospital recovering, many of whom have a long road ahead of them.

Middlemore Hospital's chief medical officer Peter Watson said some of the injured were still in life-threatening conditions, with the National Burns Centre still at maximum capacity.

"Some of them are still unwell and in our intensive care unit, and others are making good progress - we're hoping they'll actually be able to leave hospital in the coming weeks."

Thirteen are still in New Zealand hospitals, including four in critical condition, and another 12 are in Australian hospitals. Eight are in Middlemore, two in Waikato, two in Hutt Valley, and one in Christchurch. All four hospitals have specialised Regional Burn Units.

Dr Watson said some patients still needed major surgery, including more skin grafts, while some have had all the surgery they need and are now moving into rehabilitation.

Injured Australians were able to transferred back home, but not tourists from other countries.

"To date we still have all of the other overseas visitors here, but we would hope that a number of them would be able to, by the end of January, be planning or actually be able to make the trip home," Watson said.

"They have to be reasonably well before we can escort them with our medical teams back to their homelands."

For scientists keeping tabs on the still off-limits volcano, nothing is certain. About 90 percent of monitoring by GNS Science is done remotely, and miraculously, a lot of the equipment survived.

There have been no further eruptions since 9 December, but the island is in a state of unrest, with gas and steam still being emitted.

GNS volcanologist Yannick Behr said from now, activity could go one of two ways.

"One scenario [is] that we've seen the height of activity, and it'll slowly decrease to what we've seen over the last few years.

"Another scenario is that this is basically the beginning of a more active period, with several eruptions. We've seen those periods at White Island in the past ... and we can't really tell which one we're heading towards at the moment."

He said they were quite certain there was fresh, shallow magma below the island, which indicated that there could yet be more activity on the horizon.

There were up to 100 eruptions a year in its most active recent period, when it almost continuously erupted in the three decades between the 1970s and 2000.

For Inman, the island is a constant reminder and monument to his brother, and will certainly be so on Thursday - a month since the eruption.

"We'll see White Island for sure first thing in the morning, like we do every morning - we'll wake up, look out to sea and see him. That's what we'll do with our family."