It's advisable to visit a doctor as early as possible before you travel to allow time to complete any courses of vaccinations you need. If you have any longstanding medical conditions, or are travelling with small children, consult your doctor and take any necessary medicine with you. It's also wise to get a dental check-up, and if you decide to take a course of anti-malarial tablets, start taking them before you go.

It's worth taking a first-aid kit with you, particularly if you will be travelling extensively outside the cities, where the language barrier can make getting hold of the appropriate medicines difficult. Include bandages, plasters, painkillers, oral rehydration solution, kaolin and morphine for diarrhoea, vitamin pills, antiseptic cream and a sterile set of hypodermics if you will be in the country for a significant period.

There's no point in being over concerned with your health while travelling in China, but it's sensible to be aware of the dangers and take sensible precautions. China is not an easy country to be in, and some visitors, particularly if they are travelling quickly or on a very tight budget, find it exhausting and stressful, thus leaving themselves vulnerable to infections. A good general tip is not to be too hard on yourself. Travel at an easy pace, and treat yourself to decent accommodation and food, at least occasionally. Take vitamin pills (you can buy them in Hong Kong and Beijing) if you think your diet is lacking in variety.

Personal hygiene is one area you can control and it pays to be scrupulous. Wash your hands often and don't share drinks or cigarettes. When in the shower, always wear flip-flops or shower shoes, provided free at most hotels - look under the bed. The smallest cuts can become infected, so clean them thoroughly and apply an antiseptic cream, then keep them dry and covered.

Water is a potential cause of sickness as its quality varies widely across the country. Don't drink unboiled tap water, or use it to clean your teeth; avoid ice in drinks, and the ice lollies sold by street-side entrepreneurs. The Chinese boil all their drinking water scrupulously, and every hotel room is equipped with a Thermos, which the floor attendant will fill for you. Chemically treated bottled water is widely available from street stalls, though it tastes disgusting. If you stick to this and drink tea or carbonated drinks in restaurants, you shouldn't need to take any further precautions. However, if you're heading off the beaten track, it's well worth taking a water purifier with you. While boiling water for ten minutes kills most micro-organisms, it's not the most convenient method. Sterilization with iodine tablets is effective, but the resulting beverage doesn't taste very pleasant and you'll probably want to filter the water as well. (Iodine is unsafe for pregnant women, babies and people with thyroid complaints.) A range of low-cost portable water purifiers, which sterilize and filter the water, giving the most complete treatment, is now available. Made by Pre-Mac, they are available in the UK from British Airways Travel Clinics and specialist outdoor equipment retailers (call 01732/460333 for details of local stockists); in Ireland through All Water Systems Ltd, Unit 12, Western Parkway Business Centre, Lr Ballymount Rd, Dublin 12 (tel 01/456 4933); in the USA and Canada, contact Outbound Products (tel 1-800/663-9262; in Canada tel 604/321-5464).

As for food , the two most important considerations are to eat at places which look busy and clean, and to stick to fresh, thoroughly cooked food. Beware of food that has been pre-cooked and kept warm for several hours. Fish and seafood are risky as local water pollution levels are extremely high, even in many rural areas. Fresh fruit you've peeled yourself is safe; other uncooked foods may have been washed in unclean water. The other thing to watch for is dirty chopsticks . The disposable chopsticks provided in most restaurants are fine but other chopsticks are often just given a quick rinse and put back on the table. If you want to be really sure, bring your own pair.

Diarrhoea is the most common illness to affect travellers, usually in a mild form while your stomach gets used to the unfamiliar food. Rest and rehydration is the only treatment required, and it will probably be over in a couple of days. The sudden onset of diarrhoea with stomach cramps and vomiting indicates food poisoning; again, rest up for a couple of days and the sickness should pass. In both cases, it is important to drink lots of water and in serious cases replace lost salts with rehydration solution (ORS); this is especially important with young children. Take a few sachets with you, buy it at any pharmacy, or you can make your own by adding half a teaspoon of salt and three of sugar to a litre of cool, previously boiled water. At the same time avoid milk, greasy or spicy foods, coffee and most fruit, in favour of bland foodstuffs such as bread, rice, dumplings, noodles and soup. If symptoms persist, or if you notice blood or mucus in your stool, consult a doctor.

Dysentery is inflammation of the intestine, indicated by diarrhoea with blood or mucus and abdominal pain. There are two varieties, bacillary and amoebic. Bacillary dysentery has an acute onset with discomfort, fever and vomiting, plus severe abdominal pains with bloody, watery diarrhoea. In mild cases recovery occurs spontaneously within a week, but a serious attack will require antibiotics. Amoebic dysentery is more serious as bouts last for several weeks and often recur. The gradually appearing symptoms are marked by bloody faeces accompanied by abdominal cramps, but no vomiting or fever. If left untreated, amoebic cysts enter the bloodstream and may cause long-term problems, but a prompt course of antibiotics should restore you to health.

Giardia is distinguished by smelly burps or farts, discoloured faeces without blood or pus, and fluctuating diarrhoea; left untreated, these symptoms disappear but recur around once a month. Again the disease is treatable with antibiotics under medical supervision. If you're heading for Tibet, however, where the disease is most likely to be a problem, you will not be able to get the appropriate antibiotics there, so take some Flagyll with you.

Typhoid and cholera are also spread by contaminated food or water, generally in localized epidemics. The varied symptoms of typhoid include headaches, high fever and constipation, followed by diarrhoea in the later stages. The disease is infectious and requires immediate medical treatment but it's also difficult to diagnose. The first indication of cholera is the sudden but painless onset of watery and unpredictable diarrhoea, later combined with vomiting, nausea and muscle cramps. The rapid dehydration caused by the diarrhoea rather than the intestinal infection itself is the main danger. However serious the vomiting and diarrhoea you can treat cholera with plenty of oral rehydration solutions, but if you can't retain enough fluids, get medical help.

Finally, if you're suffering from diarrhoea, remember that oral drugs such as anti-malarial and contraceptive pills pass through your system too quickly to be effectively absorbed.

Malaria is not widespread in China; it's only a problem in the south in summer and all year round in tropical areas such as Hainan Island. Even there it's not common, but you should still take precautions. The key measure is to avoid being bitten by mosquitoes which carry the disease. Though mosquitoes lurk all day in dark, humid environments like bathrooms, they are most active at dawn and dusk. At these times wear long sleeves and trousers and avoid dark colours. Use repellent on exposed skin. Sprays and lotions containing about forty percent DEET (diethyltoluamide) are effective and can also be used to treat clothes, but the chemical is toxic; keep it away from eyes and open wounds, and follow the manufacturer's recommendations carefully, particularly with young children. DEET has been known to cause bad dreams, nausea and dizziness. Good alternatives based on natural ingredients are Mosi-Guard Natural and Gurkha repellents.

Most hotels and guesthouses in affected areas provide mosquito nets but you may want to bring your own if you intend heading to any rural areas. A net which hangs from a single point is the most practical. Many nets are already impregnated with pyrethroids, but need retreating every six months; all the gear is available from travel clinics and good travel shops. Tuck the edges in well at night, sleep away from the sides and make sure the mesh is not torn. Air-conditioning and fans help keep mosquitoes away, as do mosquito coils and knockdown insecticide sprays , both available in China.

If you're travelling in a high-risk area it is advisable to take preventative tablets , although medical opinion varies on the safety and effectiveness of the different drugs available. Mefloquine is widely regarded as the most effective since the malaria-carrying mosquito is now largely resistant to chloroquine. However, mefloquine has some unpleasant side effects such as dizzy spells, nausea and neuropsychiatric disturbances, which can persist after you've stopped taking the drug; ensure you discuss any concerns you have with your prescribing doctor. Women in the first months of pregnancy or during lactation should avoid mefloquine and it's also important not to get pregnant for three months after taking the drug. The most common alternative is daily proguanil (Paludrine) combined with weekly chloroquine (Avloclor). Note that you need to start taking tablets at least a week before exposure, and then continue with them for four weeks after leaving a malarial region. Many doctors in Australia are now prescribing Doxycycline, a low-level antibiotic, as a malaria preventative, and it is used as standard by the Australian Army.

None of these precautions is infallible, however. Symptoms of the onset of malaria are flu-like fever with intense headaches and shivering, with later joint pain. A blood test will confirm the diagnosis and, if caught early, treatment can be quick and effective. If you can't get to a doctor straight away, take 600mg of quinine three times a day for seven days.

The biggest hazard to your health in China is the host of flu infections that strike down a large proportion of the population, mostly in the winter months. The problem is compounded by the overcrowded conditions, chain-smoking, pollution and widespread spitting, which rapidly spreads infection. Initial symptoms are fever, sore throat, chills and a feeling of malaise. Afterwards, severe coughing and bronchitis set in, making for some very uncomfortable nights. Initially, try drinking lots of fluids and get plenty of rest. If symptoms persist, you are advised to take an antibiotic such as Tetracycline, available at pharmacies or on prescription from a doctor. As with all antibiotics, it is important to complete the course, usually four tablets daily for five days.

More serious is tuberculosis , a respiratory disease transmitted by inhalation, and spread by coughing and spitting - so it's not hard to see why China has a high incidence. The disease becomes active when the body is weakened by fatigue, other forms of illness, or malnutrition. It strikes at the lungs and in a small number of cases can be fatal. There is no need for visitors to be overly worried about the disease, though budget travellers, who spend a lot of time on crowded trains and buses, are likely to be more at risk than other tourists. Those embarking on prolonged travel should consult their doctor about their TB-immune status - many people are immune thanks to previous, mild infections.

It is doubtful that China was ever as strictly moral as the government suggests, a place where prostitution didn't exist and sexually transmitted diseases were a foreign problem, but it's certainly not true now. In the contemporary, more liberal climate, with a burgeoning sexual revolution, STDs have become much more common. As yet, though, China has only a minor problem with AIDS , though there are bound to be more than the official number of two thousand cases in the country. Paranoia about the disease, and its transmission by foreigners, is rife, however, and you may find that if you turn up at a Chinese hospital the first thing they will do is test you for it. There have even been cases of hotels burning their bedsheets after foreigners have stayed in them.

The more common diseases, gonorrhoea and syphilis , identifiable by rashes around the genitals and painful discharge, are treatable with antibiotics, available from doctors. As ever, it is extremely unwise to contemplate unprotected casual sex. Local Chinese condoms vary in quality, but imported brands are available in big cities. If it becomes essential for you to have an injection or blood transfusion in China, try to make sure that new, sterile needles are used - to be sure, bring your own. Similarly, don't undergo acupuncture unless you are sure that the equipment is sterile.

Parts of China are tropical and here it can require a couple of weeks to acclimatize to the temperature and humidity, during which time you may feel listless and tire easily. Don't underestimate the strength of the sun in tropical areas such as Hainan Island, in desert regions such as Xinjiang or very high up, for example on the Tibetan plateau. Sunburn can be avoided by restricting your exposure to the midday sun and by liberal use of sunscreens, sometimes available in China. Dark glasses help to protect your eyes and a wide- brimmed hat is a good idea. Drinking plenty of water will prevent dehydration , but if you do become dehydrated - signs are infrequent or irregular urination - drink a salt and sugar solution (see under "Intestinal Troubles"). Heat stroke is more serious and may require hospital treatment. Indications are a high temperature, lack of sweating, a fast pulse and red skin. Reducing your body temperature with a lukewarm shower will provide initial relief. High humidity causes heat rashes , prickly heat and fungal infections . Prevention and cure are the same: wear loose clothes made of natural fibres, wash frequently and dry off thoroughly afterwards. Talcum or anti-fungal powder and the use of mild antiseptic soap helps too.

At the other extreme, there are plenty of parts in China that get very cold indeed. If you're trekking in Tibet or visiting northern China during the winter, it is essential to be prepared. Hypothermia , where the overall body temperature falls, is the most serious condition, and can be fatal. Symptoms are exhaustion, numbness, slurred speech and dizzy spells. To prevent the condition, wear lots of layers and a hat, and try to stay dry and out of the wind. Sugary food will help raise the body temperature but alcohol lowers it. To treat hypothermia, try to get the victim into shelter, away from wind and rain, give them hot drinks and easily digestible food, and keep them warm.

Pharmacies , found in all towns, can help with minor injuries or ailments. Larger ones sometimes have a separate counter offering diagnosis and advice, though you're very unlikely to find staff who can speak anything but Chinese. The selection of reliable Asian and Western products available is improving (though always check expiry dates on brand-name products), and it's also possible to treat yourself for minor complaints with herbal medicines. Contraceptives are widely available, as are antibiotics. You'll have to ask for what you want, so take along a phrasebook or a Chinese speaker. The staff will usually be able to help if you describe your symptoms.

Large hotels usually have a clinic for guests offering diagnosis, advice and prescriptions - ask an English speaker from the reception desk to accompany you. Beijing, Shanghai, Guangzhou and Hong Kong have clinics specifically for foreigners where staff speak English. If you're interested in being treated with traditional Chinese medicines - of most use for minor and chronic complaints - many hospitals have attached traditional institutes, while some hotels have their own massage or acupuncture services. If you are seriously ill, head straight to a hospital - the local CITS might be able to give you useful advice in an emergency. Addresses of clinics and hospitals can be found in the "Listings" sections under major towns and cities. You will be expected to pay for your treatment on the spot, but it should not be too expensive, although foreigner surcharges may well be added. Keep all medical bills and receipts so you can make an insurance claim when you get home.