A worrier's guide to risk

They're the illnesses we fear the most. But how much of a threat are they really - and which diseases should we be concerned about?

HIV/AIDS

THE PERCEPTION

For the worried well, the fear of being HIV positive is never far away. "It's not even necessarily related to unprotected sex," says Dr Graham Archard, vice chairman of the Royal College of General Practitioners. "GPs regularly see adolescents with mouth ulcers who've never had sex, but who are convinced they've got Aids." Because there is no cure yet for Aids and effective therapies are reportedly beginning to fail, becoming HIV positive is still widely seen as a death sentence.

THE REALITY

The number of heterosexuals who have been diagnosed HIV positive has risen dramatically in the last 15 years, with around 3,000 new diagnoses every year. Homosexuals account for 45 per cent of all the 58,000-plus people living with a HIV-positive diagnosis, while only around 4,000 acquired the virus through injected drug use. The risk of developing Aids in the UK is minute compared to Africa, however. And with the introduction of Highly Active Antiretroviral Therapy (HAART) in 1996, the number of people with HIV who go on to develop Aids has reduced dramatically. But it's not an undiluted success story. "Antiretroviral drugs have unpleasant side effects and resistance can occur, even if people miss the medicine only occasionally," says Annabel Kanabus, director of the Aids charity, Avert. Even so, there are sufficient alternatives to keep almost everyone with access to Western drugs alive and well, and different classes of drugs should soon become available for people now faced with limited options for treatment.

RISK FACTOR

Low, but not to be ignored. You're right to be concerned because exercising care and caution really can help you avoid this illness, unless you are unfortunate enough to have been born with it.

WHAT TO DO

Only one in two people always use a condom with a new sexual partner - putting themselves at risk of HIV and other common sexually transmitted infections, including chlamydia, genital warts and genital herpes. Make a joint trip to an STD clinic the start of a new relationship.

BREAST CANCER

THE PERCEPTION

Breast cancer is the most common cause of death from cancer in women and it's on the increase in younger women.

THE REALITY

Although one in nine women develop breast cancer, modern therapies have nearly doubled the odds of surviving it. Two out of three women who are now diagnosed with it will survive for 20 years, as will three out of four women who are diagnosed with it after they have reached 50. Jackie Harris, a clinical nurse specialist at Breast Cancer Care, says: "A woman aged 40 has a one in 200 risk of developing the disease, but our helpline is often jammed by young women anxious about entirely normal symptoms." There are fears that the wrong group of women are being targeted by the press. "The worst-case scenario," says Dr Graham Archard, of the Royal College of General Practitioners, "is the woman in her 60s who says, 'I've had this lump in my breast for years but I haven't bothered you about it because it doesn't hurt.'"

RISK FACTOR

The younger you are, the lower the risk. The risk of dying from breast cancer is getting lower all the time. Not worth losing sleep over - just be breast aware

Early diagnosis gives women the best chance of survival. See your GP if you find a lump or thickening in the breast or armpit region, a change in the size or shape of a breast or nipple, dimpling in the skin or a blood-stained discharge from the nipple.

PROSTATE CANCER

THE PERCEPTION

Heightened publicity about the high risk of developing this most commonly diagnosed male cancer (a one in four risk during their lifetime) scares increasing numbers of symptomless middle-aged men to ask for a blood test for elevated PSA (Prostate Specific Antigen).

THE REALITY

Although around 32,000 cases are diagnosed every year, the number of people who go on to die of prostate cancer is much less - around 10,000. This means that the majority of men diagnosed with the disease actually die of something else. What's more, there is a growing body of evidence that there are two different forms of the disease and that the most common form is so slow-growing that it will never become fatal. Unfortunately, there is no test at the moment that can distinguish between the two types of cancer. Another risk factor is that one in two men become impotent and one in 20 incontinent as a result of both prostate cancer surgery and radiotherapy, the main alternative to surgery.

RISK FACTOR

One in three men over 50, and one in two over 80 have cancerous cells in their prostate. Yet only one in 25 men will die from this disease, most of them very late in life.

WHAT TO DO

Prostate Cancer UK ( www.prostate-cancer.org.uk) does not recommend PSA testing without the presence of symptoms - even though it recognises that lives can be saved when prostate cancer is picked up in healthy men. One possible solution is to have the PSA test and then, if it is positive, have "active monitoring". Recent research at the Royal Marsden Hospital in London suggests that a blood test every three months and a biopsy every two years picks up cancers in plenty of time. "It's important that men understand the real risk of the cancer before embarking on treatment," says researcher Dr Chris Parker.

AVIAN FLU

THE PERCEPTION

Britons appear to be keeping a level head about the threat of bird flu. While poultry sales in Europe have slumped by up to 80 per cent, UK supermarkets are reporting business as usual. One internet conspiracy theory blames American leaders for whipping up the scare, in order to make money out of the anti-viral drug Tamiflu. Yet reports of Government stockpiling of this drug, along with an increasingly desperate search for a vaccine, means we are keeping a watchful eye on swans - and wondering whether, having survived AIDS, Creutzfeldt-Jacob disease and nuclear obliteration, the birds will finally finish us off.

THE REALITY

H5N1 is a dangerous strain of flu that is showing an unprecedented capacity to jump the species barrier. When it does affect humans, the mortality rate is very high. At the same time, scientists worry that a flu pandemic is way overdue. The fear is that H5N1 could mutate, creating a new subtype of flu virus to which few humans would have natural immunity. The worst recorded such pandemic was in 1918, which killed 50 million. The Health Protection Agency estimates that an avian flu pandemic could kill up to 700,000 Britons. On the other hand, H5N1 has been around for nine years and so far has been responsible for only 200 deaths. Compare that to the 4,000 deaths and 2.7 million visits to casualty as a result of accidents in the home every year and it's probably a good idea to get your stair carpet fixed before you go shopping for Tamiflu.

RISK FACTOR

Very uncertain. The worst-case scenario of 700,000 deaths in UK means that we all have just over a 1 per cent chance of catching avian flu. Scientists are not sure whether the very young and very old would be more at risk - as happens with ordinary flu epidemics.

WHAT TO DO

Normal flu-prevention activity is a good idea, including washing hands regularly and avoiding being in the line of fire of splutterers and sneezers on public transport. Sambucol, an extract of black elderberry, has been shown to fight bird flu virus in test tubes - start taking it now if you're anxious.

INFERTILITY

THE PERCEPTION

Currently, one in six couples have a problem with conception. But scientists predict that within 10 years, one in three couples are likely to have problems conceiving, due to a combination of low sperm count, obesity and the ageing eggs of women who wish to establish a career before motherhood.

THE REALITY

The risk of infertility has not changed significantly over the years - though women today are waiting longer before deciding to have children compared to 20 years ago, and are therefore having slightly more difficulty in achieving and maintaining a pregnancy. The biggest change, however, is in expectation, particularly in women who have come off the Pill after several years of use. "When couples decide that they want a baby, they expect to be able to dictate when it will happen. They assume that pregnancy should occur instantly and are left with the impression that any delay is an indication that they have a fertility problem," says Professor Lesley Regan, a gynaecologist at St Mary's Hospital, London.

RISK FACTOR

Only one in 20 couples currently seek IVF treatment and experts believe that far fewer need assistance with conception - provided they are prepared to wait.

WHAT TO DO

Sign up for a consultation at the Zita West Clinic in Harley Street (£140), which offers psychosexual counselling along with physiological tests. "We regularly see couples where the man knows the exact consistency of his wife's vaginal mucus and is used to being ordered home early on fertile days," says West, whose therapy protocols will be presented at a leading gynaecological conference next month. "The mind/body link to conception is far greater than most couples realise. People who want a baby should focus on a healthy lifestyle."

What you should be worried about

Depression

Up to 10 per cent of people are likely to be depressed at any one time - with one in five suffering at least one episode in their lifetime. Women are twice as likely to become depressed as men, particularly after having a baby. "One in three new mothers are still depressed after a year, with significant adverse consequences for both mother and child," says Dr Roch Cantwell, a perinatal psychologist at Glasgow University. "Greater awareness of the risk of this disorder by family, friends and health professions could prevent enormous suffering for a large number of people."

Heart disease

Huge strides have been made in the treatment of heart disease with 30 million prescriptions for cholesterol-lowering drugs every year and a busy programme of heart bypass and angioplasty operations. Yet more than 106,000 people still died of heart-related disease in 2004, a third of whom are under the age of 75. "We have become pretty good at managing the disease when we know it's there," said Peter Weissberg of the British Heart Foundation. "Fewer people die when they have a heart attack. The problem is that we have done nothing to prevent the disease occurring in the first place." The foundation recommends a five-step plan to prevent heart disease: healthy eating, an active lifestyle, giving up smoking, cutting down on alcohol and reducing excess weight.

Diabetes

More than one million people in Britain have diabetes and don't know it - putting themselves at risk of high blood pressure, stroke, nerve damage, heart disease, poor circulation and kidney problems. Symptoms include increased thirst, excessive trips to the toilet to urinate, tiredness and genital itching.