Why nasty flu may take deadly turn

[Guest guest]

Researcher explains how virus can fatally infect lungs

BY ELISE STOLTE, EDMONTON JOURNALNOVEMBER 9, 2009

The H1N1 influenza virus seems to infect tissue deeper in the lungs than other

strains of the flu, which is one reason why more healthy people are falling

seriously ill, says Dr. Lynora Saxinger, an associate professor of medicine at

the University of Alberta and a specialist in infectious diseases.

People who end up in intensive care units with H1N1 often develop a rare type of

viral pneumonia, she says.

Bacterial pneumonia is more common, and usually shows up after a person has

started getting better from the flu. Bacteria grow in the lungs while the person

is still weak.

With viral pneumonia, the flu virus itself infects the deepest tissues of the

lungs. Scientists don't fully understand why, but that's what seems to be

landing younger people in the hospital. The lungs become inflamed, the thin,

delicate tissues grow thick and the body struggles to absorb oxygen.

Most people who end up in intensive care start to get sick, then rapidly feel

themselves getting sicker and sicker without a levelling off, Saxinger said.

" Those are the people who become very short of breath quickly. "

The influenza virus has adapted itself to infect the membranes in the upper and

lower respiratory tract, in the nose, throat and lungs, Saxinger said. It

changes form slightly year by year to get past the body's immune defences.

The virus itself is basically a shell filled with DNA, or its simpler form, RNA,

the programming script that dictates what an organism looks like. The virus has

no way of growing or reproducing unless it hijacks a host cell, forcing it to

spend all of its energy on making more copies of the flu virus. Then it pushes

the new viruses out to to infect others and the first cell dies.

The process also irritates the throat and airwaves, which makes the sick person

cough, spreading more viruses in small droplets to others.

They can live on a surface for days, waiting for someone else to touch the door

handle and then put their hands to their mouths or eyes.

When a person feels sick, they don't feel the presence of the invading virus,

Saxinger said.

They feel their body's response to the virus as tries to contain the infection.

When the cells detect the presence of the virus, they make proteins that alert

other cells and the body's complex immune system ramps up. The infected tissues

swell, the flow of blood changes, and the nose and airwaves increase the

production of mucus. This also makes a person cough, which is good for the body

because it helps to get rid of the virus and any weak, infected cells that

slough off from the wall of the throat.

Scientists don't entirely know why the flu makes a person feel sore all over,

Saxinger said. But a big part of the immune response is the production of

cytokines, " molecules produced by immune cells that affect every part of your

body in different ways. " They're meant to help, but they make you feel achy and

sick.

When people react to the type of flu vaccine given in Canada, they are reacting

to dead forms of the virus, which can't reproduce. But the body still gears up

to fight the invader. The person feels briefly sick but it's a good sign,

Saxinger. said " I always say, good for you. You're making yourself some good

immunity. "

The main kind of anti-viral medication, Tamiflu, works by preventing the

infected cell from releasing the thousands of new viruses it created. Instead,

it hangs on to them until a white blood cell comes along, engulfs the infected

cell and its viruses, and destroys them all. But the medication works well only

if the sick person takes it within the first three days.

Cases like that of Evan Frustaglio, the 13-year-old hockey player from Toronto,

who collapsed suddenly and died, are extremely rare. He complained of a sore

throat on a Friday night and died the following Monday.

" That's the point that scares everyone about that case, " Saxinger said. " It

seems like I can't just rely on my own judgment anymore. But really, mostly you

can.

" Any time you have an infection that can infect up to a third of the population,

you're going to see the full range (in severity) of responses to that

infection. "

People are probably getting too scared about this pandemic, she said. " It's

something to take seriously, certainly it is a real phenomenon and many more

people than usual will get sick. But I think people are losing track of the fact

we have an influenza epidemic every year. "

Even in an atmosphere where it everyone is on edge, " reasonable prudence and

logic is enough. You don't have to lose your mind with fear. "

The good news in this pandemic is that after the initial mutation, the virus

seems to have changed very little. Few people have immunity to H1N1 because its

genetic code is a combination of avian, swine and human influenza viruses, and

only those older than about 55 have been exposed to a virus that looks anything

like it.

But when the scientists picked a sample to make the vaccine in May, they picked

a good sample strain, and the vaccine so far appears to give solid immunity

against the H1N1 pandemic strain.

Without a vaccine, a person's immune system recognizes the invading virus and

starts developing antibodies, but it takes days to even build up enough to help

clear the virus. A normal case of influenza take about five to seven days to get

over.

A vaccine jump-starts that process, so that by the time the live virus comes

along, there are plenty of antibodies already in the blood to identify it, clamp

onto it, and prevent it from infecting any cells, Saxinger said. " It neutralizes

it. "

Provincial lab tests are showing that 90 to 97 per cent of the flu cases coming

in now are H1N1, so if a people have been seriously ill with classic flu

symptoms--fever, aches and a cough--they probably already have immunity.

But there are still cold viruses and other respiratory infections circulating.

The sniffles could be a mild case of the flu, but also could also be unrelated.

Her advice on the flu vaccine: " We don't know how long this flu season will

last. If you haven't been sick yet, get it. "

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