Hepatitis infection is on the increase - but only a minorityof those infected are aware they have it. If an early death, following years of expensive illness, is to be avoided then early diagnosis and immediate treatment is essential, writes Dr Thomas Stuttaford

Pamela anderson, actress and former Playboy pin up, will very probably be resting for up to a year from next December. This is no stage euphemism to disguise her inability to find parts, or that her popularity is waning, but is dictated by a wise, and well publicised, decision to receive life saving treatment for hepatitis C.

Hepatitis C, like hepatitis A and B, is a virus which targets the liver and in time causes liver damage. It is known as the silent killer because the initial symptoms are sometimes so trivial, and their origin from the liver so unobvious, that they remain unnoticed and unlinked to whatever incident initially caused the infection. After many years, sometimes up to 20 or 50 years later, the infection, which has been smouldering in the liver, produces enough liver damage for the patient to suffer from general malaise - the medical term for not feeling well. Hepatitis C is becoming an increasingly common cause of the well known, and diagnostically demanding, syndrome TATT - tired all the time. The general malaise progresses, if not treated, to more obvious signs and symptoms of liver damage and in a proportion of cases the cirrhosis, which has resulted from this, induces end stage liver damage and death, and occasionally the damaged cells undergo malignant change.

In my youth all types of infectious jaundice were lumped together as viral hepatitis. Increased knowledge has shown that there are now at least six different types of specific viral hepatitis - labelled from A to G - and that other unrelated viruses may also cause hepatitis. Even within these major groups there are subdivisions. There are, for instance, also six different major genotypes of hepatitis C. Unfortunately the most common genotype of hepatitis C to be found in the UK is genotype 1, which is also the most difficult to treat.

Hepatitis A is the form of infectious hepatitis caught from food and drink contaminated by sewage. It is therefore associated with poor sanitation, particularly in hot climates, and is too often the sequel to unwise holiday meals. Immunisation against hepatitis A is available. Its symptoms are very variable but even in a reasonably severe attack they are not only acute, but devastating. Fortunately full recovery is the rule in hepatitis A because it doesn't lead to the development of cirrhosis and lasting liver damage.

Hepatitis B is caused by a totally different virus which is spread by blood, blood products and bodily fluids. In the UK the major groups of people in danger of developing hepatitis B are those who come in contact with blood - such as intravenous drug users, medical workers, care assistants, and those who are exposed to many different peoples' bodily fluids, including prostitutes. In the developing world hepatitis B is frequently transmitted at the time of, or soon after, birth. Its initial symptoms, if not complicated by another infection, are usually in comparison to hepatitis A relatively mild. But so many patients proceed to liver failure after infection with hepatitis B that it is the commonest worldwide cause of death following an infection. Immunisation against hepatitis B is possible and is routinely carried out in people in risk groups. Now that distant travel is becoming easy, and populations global, a strong case can be made for extending hepatitis B injections to the population at large.

Hepatitis D is a virus which complicates patients already infected with hepatitis B. Hepatitis E is spread by contaminated water, it is only common in developing countries. Hepatitis E is only life threatening in pregnancy and doesn't lead either to the carrier state or to cirrhosis. Hepatitis F may not be a separate virus at all and hepatitis G is spread by blood but is rare.

One hundred and seventy million people worldwide - three per cent of the world's population - have, like Pamela Anderson, been infected by this blood-borne disease. The estimated number of people in the UK who are hepatitis C positive, which is lower than in many parts of the world, varies considerably, but there is a general agreement that it is between two and four hundred thousand. The prevalence isn't scattered uniformly throughout the population as the risk isn't evenly distributed. Any occupation, or habit, which carries the hazard of coming into contact with contaminated blood, or less often other peoples' body fluids, increases the chance of becoming hepatitis C positive. In Ms Anderson's case she is certain that she picked up the virus from using the tattoo needles she shared with her former husband.

Forty per cent of those who are found to carry the hepatitis C virus, unlike Ms Anderson, have no identifiable risk factor. In the past many cases were spread by blood transfusion, and the use of blood products in medicine, but this source has now been eliminated by screening. Very reasonably patients with hepatitis C strongly resent the assumption that this is exclusively a junkie disease and therefore undeserving of public sympathy. Although over 50 per cent of regular intravenous drug users have become infected, a large number of people who harbour the virus have never used drugs by injection and are deeply offended by this suggestion. There are also many people who perhaps experimented once or twice in long forgotten student days, who could neither then nor now be described as being junkies, who unfortunately caught hepatitis C as the result of a misguided adventure. Hepatitis C may also be spread by semen. Other bodily fluids may spread hepatitis C but in practice this only seems to represent a problem in those who have a very large number of partners.

The recent decision by NICE to approve the use of pegylated interferons in combination with another anti-viral drug ribavirin offers hope to those like Pamela Anderson who might otherwise have suffered cirrhosis, liver failure and in a minority of cases (three per cent per year once cirrhosis has developed) cancer. The latest trials have shown that over 50 per cent of patients may expect to be cleared of the virus by treatment but this therapy is not pleasant and the principal side effect, as Ms Anderson and others will discover, is the feeling that they will have to endure the symptoms similar to those of a bad attack of flu for 12 months.

Hepatitis C has presented a challenge. Twelve years ago, when the first treatment for it was introduced, only six per cent of the people with it were cured. Now with the introduction of Pegasys and Pegintron (uniquely known in the UK as Viraferonpeg), particularly when used with the anti-viral ribavirin, over 56 per cent can expect a good result. If infected with some of the six genotypes, results that patients might expect are even better. The factors which influence the likelihood of treatment being successful include the genotype of the hepatitis C virus involved, the absence or otherwise of cirrhosis, body weight, the age of the patient (preferably they should be under 40) and some studies have suggested that the gender of the patient is also relevant. Co-existing infection with HIV is also highly significant.

Hepatitis is a silent killer and as such probably only a minority of the people who have been infected are as yet aware of this. If an early death following years of a lengthy and very expensive illness is to be avoided, early diagnosis, and, whatever its expense, immediate treatment, is essential.