Swine flu is on a lot of people's minds right now, so for those who are worried, here are a few facts.

What is a pandemic?

You could be forgiven if your first reaction is panic at the word 'pandemic'. In the past, the WHO defined an influenza pandemic as causing "enormous numbers of deaths and illness". By contrast, the current definition requires only "community-level outbreaks" in two continents at the same time. They have changed their definition - trouble is, most of us hear 'pandemic' and think of the old definition. 

Is swine flu more deadly than other flu?

No, it isn't, but it's new, so fewer people have immunity to it, which means more people will get it and therefore statistically more people will die of it. Worst-case scenario is currently about 65,000 deaths. Remember, this is a worst-case scenario, not a prediction. The Government has to prepare for the worst, but it will probably be much, much lower than this. To give you a comparison, when the recent bird flu broke out, the worst-case scenario in the UK was 750,000 deaths, not one of which came to pass.

How does it compare with other illnesses?

In 2007, 155,484 people died of cancer in the UK.

In any given year, about 150,000 people have a stroke.

In any given year about 115,000 people die of smoking-related illnesses (including cancer, stroke, heart attack and COPD).

The Hong Kong flu of 1968 killed about 30,000 UK citizens (out of a population of about 55 million, in contrast to today's 60 million).

98% of people who get infected will recover fully without any hospital treatment.

You have a one in three chance of getting cancer in your lifetime - about the same chance as catching this flu. 

What are the symptoms?

The important one is fever - which is a temperature of 38ºC (100.4ºF) or above. This is the key symptom, combined with other complaints which may include a cough, sore throat, body aches, chills and aching limbs. Some people with the virus have also reported nausea and diarrhoea. Most people feel ill for about five days and are better in about a week. If you don't have a fever, you almost certainly haven't got the flu, though you may have a bad cold, bronchitis or something else. 

How many people have got it?

Who knows? The statistics aren't worth much. Lots of people have it and haven't contacted a doctor because their symptoms aren't bad enough. Lots of people probably carry it and don't have any symptoms at all. Quite possibly, two thirds of people won't get it.  See picture of iceberg. 

Can I avoid it?

It's going to be with us for four or five years, so if you don't encounter it this year, you'll probably encounter it in the future.

Is the virus mutating?

Of course it's bloody mutating - that's what viruses do. But it's not mutating into a worse version of itself. In fact, it might mutate into a milder version of itself. We continually hear that the 1918 virus mutated into a more deadly form in its second wave but in fact the scientists aren't sure that the flu that hit in spring 1918 was even the same flu as the autumn 1918 version because no-one has found a body to exhume to provide any verifiable data. 

If flu rates are high now, in summer, will they be worse in winter?

Possibly, possibly not. It might be that it moves so quickly in summer that infections peak sooner rather than later and winter rates will be lower than expected. 

When will the vaccine be ready?

September, October, this year, next year....The goalposts keep moving on this one. Chances are, the scientists will tweak an existing vaccine.

* Children under five. This is because any disease in a child under five can be serious but in the case of this flu, children's very active immune systems may over-react to the virus and this is what can kill. Children are also more likely to catch the virus in the first place because they attend schools, have their heads together, etc, in the same way that they are exposed to head lice more than adults are. Now that the English schools have broken up for summer it is possible that transmission rates will fall. 

* People under 20, because they have no immunity from previous outbreaks and because their immune systems are VERY healthy and may over-react to the virus. 

* Elderly people who are in poor health. The frail elderly are most at risk for every kind of disease.

* People with underlying health conditions such as severe asthma, emphysema, chronic bronchitis, AIDs or HIV, diabetes etc. The more severe the condition, the higher the risk.

* People undergoing chemotherapy or immunotherapy for conditions such as cancer, IBD or rheumatoid arthritis. Note that it is not so much the disease that increases your risk in this case, it is the treatment, which lowers your ability to fight infection. 

* The obese, particularly the morbidly obese. Of the people in the US with 'no underlying health conditions' who have died of this flu, evidence suggests that the vast majority were obese. 

* Pregnant women, because pregnancy lowers your immune system.

* Hazarding a guess here: smokers, rough sleepers, intravenous drug users, alcoholics, etc. 

Well, that's pretty much all of us then, isn't it? Actually, it's at least a third of the UK population. Including me, by the way.  

* Avoid people who've GOT the flu. If people around you are coughing and sneezing, get out of there - the virus is predominently airborne but carries only a few feet.

* Maintain good hygiene. It is actually quite difficult to catch flu from doorknobs, etc, but you can catch it from - for instance - shaking hands with someone with flu who covered their mouth when they coughed and then didn't wash their hands. Keep some alcohol-based hand sanitiser in your bag and in the car, keep washing your hands frequently throughout the day and don't put your hands near your mouth or eyes without washing them first (the nostrils, mouth and tear-ducts are all entry point for the virus). But don't use anti-bacterial soap - it weakens your immune system.

Stay healthy. As with any other illness, there is no better defence than simply being in good health to start with.  

Nominate a 'flu friend' who can pick up meds for you. 

Keep your levels of vitamin C high, preferably by diet, and have in a box of vitamins A, C and E with added zinc to take at the first sign of flu. 

Make sure you get plenty of sun while you can - the vitamin D helps to prevent the 'cytokine storm' which is what actually kills people with this flu. 

Take a vitamin D supplement, but be cautious - this is a fat-soluble vitamin and it is easy to overdose. 

Make sure you have enough food in your house for about two weeks so that if you get flu, you don't have to shop. Things like tins of spaghetti, ratatouille, baked beans, fish, tomato soup, and long-life rice desserts are useful as they don't need to be heated. If the flu gives you diahorrhea, remember BRAT: banana, rice, applesauce, toast - this is a good maintenance diet for diahorrhea. 

Make sure you have in a stock of paracetamol, ibuprofen or other painkillers, or Lemsips or something similar - anything that reduces your fever and makes you feel a bit better. Some of the latest 'Max' or 'Power' versions of Beechams and Lemsip are very effective combination remedies for treating flu symptoms. 

Cough syrups containing cystine thin out bronchial secretions and are useful in any respiratory illness. 

What do I do if I get flu?

Stay home - don't go around infecting everybody else.

Let your doctor know you are ill. 

Stay hydrated. Drink LOTS of water, preferably with a bit of sugar and salt in it.

Relieve your symptoms - don't suffer unnecessarily: take paracetamol or ibuprofen (see above) to lower your fever. Get plenty of Vitamin C down you. 

Keep monitoring your temperature. 

Don't rush back to work before you're truly well. 

With swine flu burgeoning in the UK and the death toll approaching 30, it might be time to take a little look at why comparisons between 1918 and 2009 may be somewhat misleading.

The Spanish Flu of 1918 was possibly the biggest killer in history - bigger even than the Black Death in terms of numbers (though not in terms of percentage of population). But 1918 is a long way from now and the western world has changed immeasurably. Even if this virus is related to the earlier virus, here are some facts about 1918.

* Many people lived below the poverty line - they were literally hungry poor.

* Every year, thousands died in childbirth and of diseases such as diphtheria, typhoid and measles. 

* Housing was overcrowded and insanitary.

* The physiology of infections, nutrition etc were not as well understood as today.

* Europe was coming to the end of a terrible war and the health of the general population was very debilitated.

* Close troop quarters and massive troop movements hastened the pandemic.

* Seriously ill people were moved (from the Front to hospitals back home), allowing the more severe form of the disease to spread, rather than the milder strain.

* Antibiotics did not exist.

* Nor did anti-virals.

* Nor did biocides such as Dettol. 

* There was no national health service and many people could not afford to see a doctor.

* There was no flu vaccine, and no prospect of one. 

* There were no government plans in place to deal with an epidemic.

* The vast majority of people who died of 'flu' actually died of secondary bacterial infections, not the virus itself. Today, these are treated with antibiotics.

* Many people lived in close proximity to animals such as pigs and fowl, much as they do in the third world today. 

In the UK today, however, people are much healthier and live much longer. Few go hungry. Rates of all diseases have dropped. The vast majority of people live in good or adequate housing and not in unsanitary conditions surrounded by animal faeces. Everyone has unlimited access to free healthcare. All have access to antibiotics and doctors. Most will have access to anti-virals. When a vaccine comes, which will hopefully be in September, those at risk will be first in line, and seriously ill people will remain at home, as they do in most flu epidemics, rather than being put on overcrowded trains. 

Flu can kill, but that is true of all flu. This flu is not more virulent than any other, but fewer people have immunity to it, which means it's probable more people will die, especially in the younger age groups (I know, this is scant comfort to parents).

If you are in an at-risk group (roughly a third of the population), you should take special care - 70 per cent of all hospitalisations are of people in at-risk groups. However, if you are over 40, you may have higher immunity to this flu due to exposure to similar viruses throughout your lifetime.

At-risk groups include:

More on swine flu later.