We thought it was almost eradicated in the UK, but TB is back. Dr Howard Lee considers the problems tuberculosis poses

TB remains an important health issue in the UK, especially in larger cities and among certain ethnic groups.

After an 11 per cent increase in the number of cases report in 2005, the number of people is now stable at this higher level, so the disease seems to be staging a comeback. Iun 2007, 8496 people contracted TB in the UK, with most cases occurring in London.

This trend is reflected worldwide. There are now more confirmed cases of TB than there were in 1950 and the most worrying feature of the current outbreak is the emergence of a drug-resistant form that's extremely difficult to treat.

Of course, tuberculosis was rife in the 19th century, causing up to 25 per cent of deaths in Europe, but the death toll began to fall as living standards improved and by the 1940s effective medicines were developed.

In fact, a few years ago, when supplies of the vaccine became scarce, routine vaccination was stopped.

What is the disease?

First and foremost, TB is a disease of the lungs. It's an infection by the bacteria Mycobacterium tuberculosis, which can spread via the blood to all organs of the body.

This means that TB can develop in the outer linings of the lungs, in the bones, the urinary tract and sexual organs, the intestines and even the skin.

There are several forms of TB

Young children usually contract primary pulmonary tuberculosis (first tuberculosis infection in the lungs), which often clears over a six to ten-week period as a child develops immunity.

But in some cases, it can progress and spread all over the lungs (progressive TB) or to other organs. Another type of infection is called reactivation tuberculosis. After the primary infection has passed, the bacteria can remain dormant.

When conditions become favourable, the bacteria become active - this may be years later. This is how older children and adults often develop the disease.

How is the disease passed on?

If an infected person is coughing or sneezing, the disease can be spread through inhalation of microscopic droplets.

Droplets, which are expelled into the air, dry out quickly, but the bacteria can remain airborne for hours. (They can be killed off, though, if they're exposed to UV light, including sunlight.)

After the bacteria are inhaled, they travel to the lungs, where over a period of six to ten weeks, a small local infection can develop. After this, the bacteria can spread through the blood.

A healthy immune system will usually cause the infection to remain dormant. Months or even years later, the disease can become reactivated in different organs, if the immune system is weakened in any way.

Signs and symptoms

There are few or no symptoms in the early stages. But children can have:

• Chronic or persistent cough with phlegm
• General illness with a persistent fever, and sweating at night
• Fatigue and weight loss and weakness may follow
• Coughing and sputum, which may be blood-tinged, follows if the disease progresses.

How is the diagnosis made?

In children, the Mantoux skin test is used when tuberculin (a substance extracted from the bacteria causing tuberculosis) is injected into the skin.

If a strong reaction occurs after 72 hours it may indicate an active infection. A Chest X-ray will confirm this and sputum will be sent for microscopic examination and culture. An accurate diagnosis takes time because the culture takes up to 12 weeks to develop.

Treating TB

The most important step is to find, isolate and treat all disease carriers until they are no longer an 'infective risk' to others.

Most children with TB can be cared for at home using a combination of drugs that are powerful anti-microbial agents - the major ones being Isoniazid, Rifampicin and Pyrazinomide.

A single tablet is available that contains all these chemicals. The course of treatment can last several weeks or even months, but it's vitally important to complete the course of medications in order to cure the TB.

Pregnant women with TB are treated urgently, to prevent the disease progressing and posing a risk to both mother and baby.

Vaccination at secondary school level

As I mentioned, senior school children used to be vaccinated. This involved injecting a live, but weakened tuberculosis bacteria (BCG), which caused the body to set up a protective mechanism, greatly reducing the risk of lung TB - and effectively preventing varieties of blood-borne TB.

A shortage of vaccine means that the BCG isn't given as a matter of routine but, if young people are travelling to Africa, Asia or Eastern Europe for a prolonged trip, they should make sure they're vaccinated.

Recent outbreaks

It's the homeless and people with other problems, like HIV infection, drug abuse and alcoholism, who are particularly at risk at the moment.

All of these conditions tend to weaken the body's general defence mechanisms. We also know that an increasing number of immigrants arriving in this country have been exposed, or may be carrying active tuberculosis from their own country.

Treatment regimes are strictly managed and observed in the UK and we probably have the lowest incidence of drug resistant TB in the world. Only around one per cent of all TB cases in the UK are caused by a multi-drug resistant strain, and only a very small proportion of these are extensively drug resistant.

Preventing TB depends on maintaining good living standards, eating well, having plenty of sunlight and taking exercise.

It also depends on vaccination but, the national schools vaccination program has now been replaced with targeted immunisation of children with an increased risk of TB - infants living in areas with a high incidence of TB, and any child whose parent or grandparent was born in a country with a high incidence.

Tuberculosis is certainly not a disease of the past. We've been lulled into a sense of false security, doctors included, and now that we take foreign travel for granted, we also need to be aware of the risks a disease like TB poses.

An undetected infectious TB victim can infect another 10 people annually - each of whom could transmit the disease.

In future, children in the most vulnerable age groups will be screened or monitored more closely, and the outlook for those children diagnosed recently is excellent.

They will receive effective treatment, long-term monitoring and declared cured by the end of the regime.