- guardian.co.uk, Monday January 10 2000 08.49 GMT
The far-flung origins of these different strains and the diverse means by which they are transmitted illustrate the greatest problem faced by doctors attempting to combat the flu virus: its ability to mutate to confound the body's immune system make it almost impossible to predict what shape it will take each winter.
A nucleus of genetic material coated in protein, the virus has the ability to change its make-up to survive. While the body may have adapted an immune strategy to combat the flu that laid you low last winter, the chances are that come next winter the virus will have reinvented itself.
There is no cure for flu. The primary tool for reducing cases during the midwinter peak is vaccination - 9m jabs were given in Britain this winter. But flu's adaptability continually confounds vaccine manufacturers.
The flu cycle begins in the Far East, where the first cases of new strains are typically detected some six months before reaching Britain. In Hong Kong, Shanghai and other Far Eastern cities that have lent their name to outbreaks, densely populated areas with imperfect hygiene, where humans and animals live closely together, provide the breeding grounds for new strains.
As the virus passes from one species to another, from chicken or pig to human, it mutates, occasionally becoming lethal on a massive scale. In 1918 over 20m people died in a pandemic of "Spanish" flu, thought to have originated in China, while in 1957 Asian flu killed 9m. An outbreak in 1968 of Hong Kong flu affected over 1% of the British population.
Manufacturers begin developing new vaccines to combat the strains as soon as they are identified, and the first consignments of vaccine generally arrive in British GPs' surgeries in October. By the time the bug arrives, however, it may have changed its protein "coat" and defeat the vaccine.
Vaccination reduces the pressure on GPs' surgeries, and many buy the vaccine and administer it to patients for free, before being refunded by the NHS at a profit of around £1 per jab.
Laurence Buckman, of the British Medical Association's general practitioners' committee, said that despite the unpredicability of the virus, vaccination was the best course of action open to GPs and patients alike.
"The vaccines are not wonder cures ... but they do stop an awful lot of people going down with the virus," he said.
"I would recommend any old person, any child, anyone with bronchial complaints, asthma or other respiratory problems to have a vaccine."
The widespread nature of the present outbreak has less to do with the strength of the Sydney strain than the collective immunity of the population, said Dr Buckman.
"What is important is herd immunity," he said. "If the herd has a low immunity to a strain, and it occurs at a time that doctors and nurses get it to, then the virus will potentially affect millions."
A big problem faced by doctors attempting to prescribe effective treatment is that patients tend to bundle together a number of symptoms under the lay-heading flu, when in fact they may be suffering from other viruses.
"The term flu is misused regularly and in both directions. People say they have flu when they just have a common cold, and similarly I have had patients who have dismissed pneumonia or meningitis as flu," said Dr Buckman.
"Flu is rather distinct in its symptoms. The sufferer will have a dry cough, a high fever and muscular aches and pains. However, flu does not give you a runny nose and it doesn't give a sore throat ... Flu is a profound malaise, people feel truly awful - if you've genuinely had flu there is no danger of you mistaking it for a cold."
To get well...
Do:
Get vaccinated
Maintain a 'comfortable' temperature. You shouldn't be cold but overheating is as dangerous
Drink plenty of liquid. You're going to sweat a lot so replace the fluid
Take two paracetamol every four hours
Try to keep temperature under 102F. Take regular cool showers to stem the fever
Don't:
Go to work. Flu sufferers are unproductive and succeed only in giving the rest of the office the bug
Expect miracles. There is no cure for flu
