Unravelling the influenza code

IN this week’s Friday science feature we look at swine flu, its causes, spread and treament, with Professor Rob Smith, Dean of Applied Sciences at the University of Huddersfield — Oldham’s university partner.

Summer flu can be a real swine! This year especially, the discomfort of a high temperature and other flu symptoms is made more stressful by reports of deaths of healthy people from a strain of influenza that we call swine flu.

It seems hardly any time since we were all worrying about bird flu, so what is it about flu and domestic animals, why are older people less likely to suffer from swine flu, and why do we have to wait weeks or months for a new vaccine?

Answers to these questions come from the new science of medical genetics. Medical genetics is about how disease is affected by the genetic material (in our case the DNA that makes up our genes) that makes offspring resemble their parents.

But the genetics of disease do not just involve variation in human DNA. The genetic material (RNA) of both human and pig flu viruses is also involved, along with defensive substances called antibodies that circulate in our blood.

A virus is a fairly simple organism that lives and reproduces by taking over the cells of more complex organisms.

Viruses that attack us find their way into vulnerable cells such as those found in the mouth, nose or eyes.

We then act as “hosts” in the sense that the viruses turn our cells into factories that make more viruses instead of supporting our normal body processes.

The virus spreads within our bodies, destroying millions of cells and causing us to spread the virus to others, for example through runny noses or other bodily secretions.

Our bodies usually fight back by making antibodies.

These are proteins that we produce to combat viruses and bacteria. Antibodies are produced in response to a “foreign” protein such as the protein coat that surrounds the genetic material of a virus, and they attach themselves to the foreign protein and neutralise the virus. We develop immunity to a virus after either we have been infected by it or we are exposed to virus protein through immunisation.

Generally we recover from infections by viruses and bacteria and retain a degree of immunity that protects us against future infection, unless the virus changes its coat.

That is why older people are less likely to suffer from swine flu than youngsters — this new virus is similar to a strain of flu that was around 40 or 50 years ago.

Viruses evolve by Darwinian natural selection, which favours those genetic variants that reproduce quickly and have a high infection rate.

Viruses bear us no malice —the fact that we suffer ill health or death along the way is purely incidental to the virus.

In fact it is usually in the long-term interests of viruses not to kill their hosts. But viruses sometimes cause great harm to human populations.

The infamous Spanish flu pandemic in 1918 killed at least 50 million people, including almost a quarter of a million in Britain.

The RNA of flu viruses changes (mutates) all the time and medical geneticists are always on the lookout for new strains that are either more harmful or more infective or, in a real nightmare scenario, both. New vaccines can be produced but it takes some time to characterise the virus and to develop a vaccine before testing for safety and producing it in large quantities.

Viruses generally specialise in infecting a particular sort of animal or plant, but they sometimes cross over between species.

This is made more likely when people live very close to their animals.

Viruses of birds, pigs and man sometimes mix RNA to make new strains of virus. New strains can be deadly if the human population is then infected by a new virus to which there is little or no immunity, as in the case of the H5N1 strain known as bird flu.

The current outbreak known as swine flu is caused by a new strain of a type of virus called H1N1.What should we be doing about it? First, there is no point in worrying – all forms of flu are unpleasant and a small number of people need hospital treatment for complications, and this is nothing new. As individuals, we can all help slow down the spread of swine flu by simple measures — wash your hands frequently using soap and warm water, keep your hands away from mouth, nose and eyes, and stay at home if you have a raised temperature or other flu-like symptoms.