The seasonal version of the H1N1 flu virus circulating today may have a far more sinister origin than first thought, with researchers saying it could be a direct descendant of the 1918 Spanish Flu strain that killed up to 100 million people.

Tiny lung fragments from people who died in the catastrophic 1918 pandemic, which wiped out millions, provided the crucial scientific clues, they said in a study.

Genes taken from the lungs of those killed more than 100 years ago, when mapped against the current H1N1 strain, suggested a genomic ancestor to our now-yearly flu, the team of international researchers found.

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Scientists analysed 13 lung specimens collected from different people between 1901 and 1931 and carefully stored in historical archives of museums in Germany and Austria.

The century-old specimens included six samples taken from Spanish Flu victims in 1918 and 1919, during the peak of the killer pandemic.

In the peer-reviewed study published on Wednesday in Nature Communications, researchers conducted molecular clock modelling, a method which allows evolutionary timescales to be estimated, and suggested that all genomic segments of the seasonal H1N1 flu could be directly descended from the initial 1918 pandemic strain.

This finding, scientists said, contradicted earlier thinking that H1N1 emerged through a process of reassortment, a phenomenon which involves the exchange of genomic segments between different viruses.

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The H1N1 virus, once commonly referred to as swine flu, caused a flu pandemic in 2009.

In 2009, the global population had little immunity to H1N1 because it was new, with the World Health Organisation estimating 100,000 to 400,000 died from the pandemic that year.

As the virus continued to circulate in people in Australia and around the world, it became a seasonal human flu virus.

The 1918 Spanish Flu caused the largest global pandemic catastrophe in the last century.

It had similarities to COVID-19, in that the virus spread worldwide, but the 1918 flu strain was far more deadly than the coronavirus, which emerged from Wuhan in China.

Spanish Flu peaked in the northern hemisphere autumn of 1918 and continued through the winter of 1919.

It is believed the virus reached Australia in 1919, causing up to 15,000 deaths, and infecting between between one-quarter and one-third of all Australians.

Australia's population at the time was about five million.

While young children and the elderly were severely affected, the 1918 pandemic caused exceptionally high mortality in healthy people aged 20-40.

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Australia's dramatic two-year drop in influenza cases is well and truly over, with cases roaring back in April, particularly in the eastern states.

"We've had an eight-fold increase from March to April," Professor Ian Barr, Deputy Director of the WHO Collaborating Centre for Reference and Research on Influenza, told 9news.com.au.

Lab-confirmed cases, which generally under-represent the reality, rose from 512 in March to 4663 in April.

"It's quite a lot of influenza for this time of year," Barr said.

"Normally, we don't see start to see these sort of rises for another month or so."

New South Wales, which leads Victoria and Queensland on April cases, should brace for a significant epidemic outbreak to hit this winter, he said.

The death of an Alabama jailer found shot in the head with a gun in her hand after a week-long manhunt has only deepened the mystery of why a trusted official would help free a hulking murder suspect with a violent and frightening history.

Vicky White, 56, was pronounced dead at a hospital after Casey White, 38, gave up without a fight in Evansville, Indiana. The fugitives had spent more than a week on the run.

NBC's Today show reported federal marshals said Casey White told officers at the scene, "Please help my wife. She just shot herself in the head and I didn't do it."

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The two Whites were not related, let alone married, officials said.

Before Vanderburgh County Coroner Steve Lockyear announced her death, the sheriff in Alabama had said he hoped to get answers from his once trusted jail employee.

"I had every bit of trust in Vicky Whit. She has been an exemplary employee," Lauderdale County Sheriff Rick Singleton said.

"What in the world provoked her, prompted her to pull a stunt like this?

"I don't know. I don't know if we'll ever know."

Authorities closed in after receiving a tip on Sunday that a man closely resembling Casey White had been recorded by a surveillance camera at a car wash getting out of a 2006 Ford F-150 utility, the Marshals Service said.

He stands 2.06 metres tall and weighs about 118 kilograms.

A local police officer then spotted a vehicle they were looking for on Monday, and members of a US Marshals task force went to investigate, leading to a brief chase, Vanderburgh County Sheriff Dave Wedding said on Today.

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"The pursuit was very short. It went up a major artery here in Vanderburgh County and they cut across a parking lot at a large factory," Wedding said.

"They were in a grassy area so three of our task force members actually rammed the vehicle, pushed it into a ditch so it ended up on its side.

"As they approached the vehicle it was obvious that the female driver was unconscious and still had a weapon in her hand. And they removed the murderer from the vehicle simultaneously."

Wedding said it has not been officially determined yet that Vicky White had in fact taken her own life.

"The coroner's office will do an investigation and they will determine if it was a self-inflicted gunshot wound," he said.

"The initial indication is that it was, but we won't rule anything out until we have a thorough investigation by the coroner."

The manhunt began April 29 after Vicky White, the assistant director of corrections for the jail in Lauderdale County, told co-workers she was taking Casey White, who was awaiting trial in a capital murder case, from the jail for a mental health evaluation. There was no such appointment.

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"We got a dangerous man off the street today. He is never going to see the light of day again," Singleton said.

"That is a good thing, for not just our community. That's a good thing for our country."

Casey White was serving a 75-year prison sentence for attempted murder and other charges at the time of his escape.

He was awaiting trial in the stabbing of a 58-year-old woman during a burglary in 2015. If convicted, he could face the death penalty.

Federal and local law enforcement officials also learned Casey White threatened to kill his former girlfriend and his sister in 2015 and said "that he wanted police to kill him", the Marshals Service said.

A warrant was issued on May 2 for Vicky White charging her with permitting or facilitating escape in the first degree.

Her family members and co-workers said they were stunned. Singleton said it appeared the plan had been in the works for some time. Jail inmates said the two had a special relationship and she gave Casey White better treatment than other inmates.

In the past several months, she bought a rifle and a shotgun and also was known to have a handgun, US Marshal Marty Keely said.

She also sold her house — for about half of market value — and bought a 2007 orange Ford Edge that she stashed at a shopping centre without license plates.

"This escape was obviously well-planned and calculated. A lot of preparation went into this. They had plenty of resources, had cash, had vehicles," Singleton said.

On what Vicky White said would be her last day at work, video showed the pair went from the jail to the shopping centre, where they picked up the Ford and left, Singleton said. Their flight was not discovered for much of the day.

A group of Perth marine scientists have made a spectacular ocean discovery, reeling in the deepest fish caught off Australian waters.

Scientists from the University of Western Australia found the fish more than 3000 kilometres off the coast of Western Australia and 6500 metres below the Indian Ocean's surface,

In the process, they may have discovered a new species.

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With backing from the Minderoo Foundation — an Australian non-for-profit aimed at solving global issues — Dr Bond and his fellow scientists snagged the two new unnamed species of Snailfish using a $100,000 piece of exploration equipment.

It was fitted with a simple $30 yabby trab and a cheap piece of PVC drain pipe.

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The small deep-sea dwellers live in temperatures of around 2 degrees and normally melt in warmer conditions.

So, the scientists had to work quickly to bring the creatures to the surface where the mercury was closer to 20 degrees.

"When we bring them up they have this gel that breaks down very, very quickly so they're quite soft, almost transparent, through their entire body so you can see all their internal organs," Dr Todd Bond from UWA told 9News.

"You can see their bones."

With very minor exploration conducted in the Indian Ocean before now, scientists are hoping the discovery will help them learn more about the waters that encircle WA.

"For us it may seem like a different world but this is one of the biggest habitats on the planet," Dr Bond said.

A NSW government proposal to slug Sydney drivers a congestion tax to travel into the city has been revealed in confidential documents.

9News has obtained a confidential report called the Future Transport Strategy prepared for the state's cabinet.

The report aims to introduce a congestion tax to encourage more Sydney drivers to swap their cars for bikes when motoring around the CBD.

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"Currently, road users do not pay the true costs of driving… charging for road use at certain locations or times can encourage customers… to choose other options," the report said.

The proposal is similar to one currently in place in the UK where drivers pay a $25 daily fee to drive within 25 square kilometres of the city of London.

In Sydney, 25 square kilometres would encompass Glebe and Camperdown to Rushcutters Bay and Centennial Park as well as Circular Quay to Redfern and Waterloo.

Drivers would be charged through a ring of cameras between 7am and 6pm Monday to Friday and midday to 6pm on weekends.

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The NSW Labor party has condemned the congestion charge proposal, claiming motorists are already being slugged too much.

"You're going to have this ridiculous situation where people will be on their bikes on the M2 because of congestion charging," opposition leader Chris Minns said.

"They can't afford to pay a cent more, let alone a daily congestion charge every time they enter the CBD."

NRMA spokesperson Peter Khoury said the proposal goes against the government's desire to bring people back into the city.

"If we want to encourage people in the short term to come bank into the CBD because the CBD is struggling, maybe this is not the best idea," Khoury said.

Not only does the government proposal suggest a congestion charge but it also intends to introduce new speed limits such as 30 kilometres per hour zones in neighbourhood road networks and local centres.

Khoury added the proposal for new blanket speed limits "does not work".

"You've got to use science and data and research and history when you are setting speed limits," Khoury said.

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Minister for Cities and Active Transport Rob Stokes refused to comment publicly and cited cabinet confidentiality.

Stokes added the report is only a draft and is yet to be adopted by the NSW government.

"Yesterday's draft is tomorrow's policy, this government's approach to tolls is motorists pay more," Minns said.