Flu

Flu and complications linked to it kill hundreds of people in the UK each year. But despite massive investment in research into the virus, there is no cure.
However, there are vaccines which have some protective effect. These are normally administered to the elderly and the vulnerable each year.
But every few years a new strain of flu appears which spreads so rapidly that precautions cannot be developed in time.
This can lead to pandemics which threaten millions of lives. The worst flu pandemic this century was the Spanish flu pandemic of 1918 which killed an estimated 40 million people - more than World War One.

What is flu?
Many people confuse flu with a common cold. There is a big degree of crossover between the two. Both are caused by viruses.
According to Cardiff's Common Cold Centre, the symptoms of a common cold include:
A scratchy, sore throat;
A blocked or runny nose;
A cough.
Common flu symptoms include:
Spells of high fever (hovering above 101°F) and chilliness;
Severe muscle aches and pains;
Followed later by the traditional cold symptoms;
Flu tends to have a more sudden on-set than a cold.
Both colds and flu tend to last for about five or six days in a normally healthy person and are transmitted in similar ways - cough, sneezing and fingers made dirty from being poked in the nose and eyes.

How to treat the flu
There is a temporary vaccine against flu and those most likely to benefit from it include the elderly, people with damaged immune systems and the very young.
These people are at greater risk of serious complications that can be fatal.
For the majority of people with flu, however, the symptoms can be treated with bed rest and over-the-counter drugs.
The most difficult symptoms to treat are aches and pains, high fever and a lingering cough.
Once a person has the flu, they should:
Take paracetamol to treat the high fever and aches and pains;
Take a linctus to treat the cough or drink lots of hot, sweet fruit drinks, such as hot lemon with honey;
Because the fever causes sweating and dries out the body, patients should increase the amount of juices, water and hot drinks they take;
Smoking aggravates the flu so patients should steer clear of smoky atmospheres;
People with a high fever and muscle pain should rest in bed. This should relieve the aches and pains and will ensure the virus is not spread.
Antibiotics are not effective against flu viruses, but aspirins can be taken, although not by children with the flu.
This is because they could be at risk of developing Reye's syndrome, a neurological disorder which is linked to aspirin use by the young.
The drug rimantadine can be used to treat influenza type A virus infections in adults - the strain now affecting the UK, but it has no effect on influenza type B infections.
However, although used to treat mainly the elderly in the US, it is not commonly prescribed in the UK and can lead to side effects.
It is not a cure, but can reduce symptoms and the length of time a person suffers fever if taken within 48 hours of the onset of flu.
Rimantadine is a derivative of the drug amantadine, which has been used to treat Parkinson's disease and causes side effects such as insomnia and dizziness.

Secondary infections
Secondary infections that develop as a complication of flu claim hundreds of lives each year.
They include pneumococcal pneumonia which can lead to bacteramia or blood poisoning.
The campaign group, Action Against Pneumococcal Infection (AAPI), says around 50,000 cases of pneumonia in the UK are caused by the flu virus every year.
Most people have pneumococci bacteria in the respiratory system, but usually they are resistant to it.
However, a bout of flu can lower that resistance, leading to pneumococcal pneumonia. Sufferers can need hospital treatment and antibiotics and some die.
The AAPI says around 20% of those who do receive treatment die and the figure rises to 40% for the elderly, very young or those whose immune system has been damaged.
There are vaccinations which can give protection against pneumococcal infection for life.

Epidemics
Scientists do not know why some viruses become mass killers, but recent research suggests a molecular mechanism may allow a virus to cause sweeping and potentially fatal damage to the body.
Normally influenza is confined to cells within the respiratory system, but some viruses have a unique key which unlocks the door to cells throughout the body.
The new discovery could allow doctors monitoring flu viruses to spot changes which might give a virus pandemic potential.
Influenza virus surface proteins alter frequently, requiring new vaccines to be developed to protect against them.
The viruses are never the same each year, but normally the surface proteins undergo slight changes.
More dangerous is a "shift" when two different viruses mix together to create a radically different strain