Professor Hugh Pennington, a bacteriologist at Aberdeen University, said underlying health problems were likely to have been a "significant factor" in the death of a woman at the Royal Alexandra Hospital in Paisley
"It's very sad but with the number of cases we have seen it is really something which was always going to happen sooner or later. Unfortunately it is to be expected," said Prof Pennington,
"This is what the authorities have been saying will happen for a long time.
"It does not point to the virus getting nastier. All the evidence to date suggests the virus is not changing at all.
"This is a flu virus, it is in no way different from an ordinary winter flu virus, so if there are enough cases some people will have to be admitted to hospital and some will die.
"I don't think anyone can read anything into it other than it's what one might expect."
He said the presence of underlying health problems was likely to be a "significant factor", adding: "It makes it more likely that they will get the serious form of the virus in the first place.
"If your lungs are already only working at half capacity when the virus kicks in and takes half of what is left, you will be left teetering on the edge.
"It raises the odds that a patient will experience serious difficulties."
Prof Pennington said it was very difficult to measure death rates from flu, but one death out of more than a thousand cases was "quite unremarkable" and compared favourably to ordinary seasonal flu.
He said anti virals could help make flu easier to manage but they were 'not a magic bullet' and worked best if administered very early on in the infection.
Patients already experiencing health problems would be more difficult to diagnose with the H1N1 virus and were therefore more likely to experience a delay before receiving treatment.
"Anti virals damp down the virus but they are not curative, and once symptoms have developed they don't work nearly as well," he said.
Patients with swine flu who were admitted to intensive care were likely to be given oxygen and help to breath.
The virus develops as pneumonia, attacking cells lining the lungs, and preventing the transfer of oxygen.
Patients respond by making secretions in the lungs, with some responding more vigorously than others.
In the worst cases patients 'effectively drown in their own secretions'.
Prof Pennington said the majority of swine flu deaths recorded in the US involved patients already suffering from significant health problems.
On Friday Health Secretary Andy Burnham encouraged people not to panic after the World Health Organisation announced the world is now in the grip of a flu pandemic, the first in more than 40 years.
He said the UK was well-prepared and the WHO's announcement did not affect the assessment of how the virus was behaving in the UK.
Dr Margaret Chan, director-general of the WHO, said the world should brace itself to see more deaths.
However, she said WHO did not expect to see a sudden leap in the number of people with fatal infections and described the current pandemic as moderately severe.
Mr Burnham said most of those catching the virus were making a full and fast recovery - though a small minority of cases have been more serious.
At present, the UK has enough of the anti-viral Tamiflu to cover half of the population but orders are in place for 50 million doses - enough to cover 80 per cent.
As far back as April 30 the Government's Chief Medical Officer Professor Sir Liam Donaldson warned there were likely to be deaths from the swine flu, just as there are with seasonal flu.
Swine flu has been making pigs ill since it was first identified in the US in 1930 but the virus has undergone a genetic change enabling it to passed easily between humans.
Experts have said a surge in the number of infections can be expected in the autumn and winter.
This was the pattern of the major flu pandemics of 1957 and 1968, both of which took off in the autumn after small scatterings of cases had been reported during the preceding summer.
The symptoms of swine flu are similar to those of most influenza infections, commonly consisting of a temperature, cough, runny nose, body aches, extreme tiredness and headache.
Some patients also suffer nausea, vomiting and diarrhoea, and a few have developed severe respiratory symptoms and pneumonia.
Yesterday, the first fatality in the UK caused by swine flu was announced.  Jacqueline Fleming, who was 38, from Glasgow, Scotland, died at the Royal Alexandria Hospital in Paisley.  She had been admitted to hospital two weeks earlier after the premature birth of her baby son, Jack.  Reports suggest that she was admitted having suffered a  and suffered further complications, in part related to the birth of Jack.

Map of the UK colour coded by severity of H1N1 outbreak, as of 14 June.
Professor Hugh Pennington, a bacteriologist at  was quoted as saying that underlying health problems were likely to have been a significant factor in Jaqueline's death.  He also dismissed speculation that the virus was getting worse, saying "This is what the authorities have been saying will happen for a long time.  It does not point to the virus getting nastier. All the evidence to date suggests the virus is not changing at all."

Her son Jack died today in the special care unit of the same hospital at the age of two weeks, having been born 11 weeks early.  He was not affected by the H1N1 virus.

Jaqueline's husband stated today "My beautiful son was born on the first of June 2009, 11 weeks early. He suffered from a number of complications and despite his brave fight he passed away earlier this evening at the Special Care Baby Unit at the Royal Alexandra Hospital in Paisley." 

On Friday, the  said confirmed swine flu cases in the UK had reached 1004.  Recently, the World Health Organisation declared the outbreak to be a worldwide .