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Q1: I think washing hands is an option. But if you really think about it, you'd be washing your hands 24/7. This is my problem: I come home from the supermarket, I drop my bags and wash my hands very thoroughly. Next, I start emptying the shopping bags touching the bags and about everything else around the kitchen. My nose itches and in a brief moment of amnesia I slightly scratch my nose ("Oh deary ME," I think). Couple of days later we are all in bed with the flu. How far can one go with washing hands and at which point does one develop a BAD? (bug anxiety disorder). Robert Berkhout, Vancouver, BC.

A: Recent research has shown that more coughs and colds are spread by infected hands than droplets. Watch out for the door knobs and hand-shaking acquaintances. Either source of infection can, of course, transmit the viruses that cause upper and lower respiratory tract infections. Most people are aware that if they go within a couple of metres - or more - of someone suffering from flu or a cold and is coughing, sneezing or blowing their nose on a soaking wet handkerchief, they are liable to become infected,. However they are less aware that failure to wash their hands before they touch their faces, rub their lips, scratch their noses just after they have opened a door with a contaminated handle, shaken the hand of someone suffering from a respiratory tract infection, shared a towel in a bathroom or pulled the same plug in a lavatory as someone with a cold, may also result in them catching whatever viruses (or in some circumstances bacteria) that are circulating.

We can't, as the reader so rightly suggests, spend our whole day washing our hands but we should wash them with soap and water, and preferably afterwards with a medicated alcohol mix from a dispenser before we eat, even if we are only going to eat a snack.

When working in a sexually transmitted diseases clinic we obviously washed our hands before and after seeing every patient. Some days I washed my hands in medicated soap thirty times during the time I was in the clinic. I also, of course, washed at home before leaving for work, when I arrived at the office and certainly as soon as I returned to my flat in the evening. At the end of the week my hands were beginning to look a bit ragged. Ordinarily, no one would try and keep flu at bay with these tactics but hand washing, care over towels and the proper cleaning of floors and surfaces with medicated cleaning materials will help.

Q2: Avian flu: I have heard that we can combat the H5N1 virus through a product (Envirocair) from a UK company called Biotech International, but nobody wants to pay for this. Why not use it in airports and on the tube in London and stop this and even C-Dif and MRSA in its tracks before these migrate into the human population in a big way? Robert Hastings.

A. There are various systems available that help to eliminate viruses and bacteria from the ducts of air conditioning systems. In other places, whether domestic rooms or offices that don't have air conditioning ducts an apparatus is available to help to reduce the bacterial and viral load of the circulating air by using ultra violet light air cleaners. I have seen these being demonstrated for use in hospitals, offices and rooms in private houses. I am afraid that I don't remember whether these appliances were manufactured by EnviroCAIR Inc. I do remember that air cleansing was recommended by the manufacturer for people who had, for example, an asthmatic child in whom infection was the trigger for an attack. Apart from the expense that was considerable, the question was also raised as to whether people should be brought up in an entirely microbe free world and what effect that would have on their immune system. This is, of course, of importance and will need investigation. As a means of controlling hospital infections an air cleansing system of the sort I have seen demonstrated would prove, so far as I could judge from the demonstration, a great advance but also a very expensive one. I was impressed at the time by the statistics and by the quality of the doctors who were recommending it.

So far as avian flu is concerned in Britain what we need immediately is to have a larger supply of Tamiflu, the antiviral agent in our stockpile (see my article). Currently we have less in stock than most of the developed countries. If we doubled our stockpile we would then have slightly less antiviral agent ready for immediate use than, for example, does France. We also need to have some Relenza stockpiled, a different anti viral that has some disadvantages when compared to Tamiflu but even so should be held in reserve in case of resistance to Tamiflu developing. We also need stockpiles of a vaccine against H5N1. Even though this wouldn't be the perfect vaccine for an avian flu pandemic once the virus had mutated it might provide a measure of resistance. Finally we need to clean up our hospitals.

Q3: I am aware that cold and flu viruses usually enter the body by the nose. In order to prevent an onset, I have started to place in my nostrils, (twice a day) a solution of tea tree, lavendar and geranium (all antiviral essential oils) in a base oil. Is this a good idea, or not? Name and address withheld.

A: The use of herbal remedies is as old as the hills but was still part of medical practice when I qualified. It is important to remember that if any herb has a pharmacological effect that can be of benefit to people it is also likely to have side effects that could be detrimental. Many herbs may compete with the metabolic pathways of proven traditional medicines and alter their effect. Others have adverse effect unrelated to their reaction with traditional drugs.

Tea tree oil was used as an antiseptic to advantage by some forces during the Second World War when there was a shortage of standard antiseptics. Lavender is an old remedy for such diverse conditions as depression, insomnia and some forms of infection. It is even supposed to keep moths at bay. In some parts of the country lavender oil is applied to the forehead to treat migraine. Geraniums are used in herbal medicine but they come in many different forms and types and I would steer clear of them unless I was a keen botanist who knew all about geraniums and herbal medicines.