The word tuberculosis, or TB as it's commonly referred to, might conjure up images of Dickensian London, but it's a disease that's still very much around today.
Dr Charlie Easmon, specialist advisor in travel medicine, looks at the symptoms, dignosis and treatment for TB today:
What is tuberculosis?
Tuberculosis (TB) is a disease caused by an infection with the bacteria Mycobacterium tuberculosis complex. During the 19th century, up to 25 per cent of deaths in Europe were caused by this disease. It used to be called the 'white death' as opposed to the Black Death caused by plague.
The death toll began to fall as living standards improved at the start of the 20th century, and from the 1940s, effective medicines were developed. However, there are now more people in the world with TB than there were in 1950, and 1.5 million individuals will die this year from this disease – mainly in less developed countries.
It is estimated that any one time, up to a third of the world's population have been infected with TB (present but not visible disease that can be reactivated by medicines that suppress the immune system, getting older or infection with HIV).
The disease is more common in areas of the world where poverty, malnutrition, poor general health, crowded housing and social disruption are present. In the UK, too, the number of TB cases is again rising. Alcoholics, HIV-positive individuals, some recent immigrants and healthcare workers are at increased risk.
The disease is most commonly found in places such as hostels for the homeless, prisons, and centres for immigrants arriving from areas with high rates of HIV infection or inadequate health provision.
What parts of the body are affected by tuberculosis?
TB commonly presents as a disease of the lungs. However, the infection can spread via blood from the lungs to all organs in the body. This means that you can develop tuberculosis in the pleura (the covering of the lungs), in the bones, the urinary tract and sexual organs, the intestines and even in the skin.
Lymph nodes in the lung root and on the throat can also get infected. Tuberculous meningitis is sometimes seen in newly infected children. This form of the disease is a life-threatening condition. Non-lung TB is an important cause of skin, bowel and gynaecological problems.
How do you catch tuberculosis?
• Lung TB
The bacteria that cause the disease are inhaled in the form of microscopic droplets that come from a person with tuberculosis. When coughing, speaking or sneezing, the small droplets are expelled into the air. They dry out quickly, but the bacteria itself can remain airborne for hours.
However, the tuberculosis bacteria are killed when exposed to ultraviolet light, including sunlight.
• Non-Lung TB
Infected milk or dairy products can cause the mycobacterium to set up infections in the gastro-intestinal tract and also affect the reproductive systems in men and women.
How does the disease develop inside the body?
• Lung TB
After the tuberculosis bacteria have been inhaled they reach the lungs and, within approximately six weeks, a small infection appears that rarely gives any symptoms. This is called a primary infection.
After this, the bacteria can then spread through the blood. If you have a healthy immune system, in most cases the infection will remain dormant without doing any obvious harm.
• Non-Lung TB
A similar process as above but the route of entry may be through the gut. Months or even years later, however, the disease can become reactivated in different organs if the immune system is weakened. The lungs are the favourite place for the illness to strike.
What are the symptoms of tuberculosis?
Typical signs of tuberculosis include:
- Chronic or persistent cough, sometimes with blood
- Lack of appetite
- Weight loss
- Night sweats
Tuberculosis can mimic many forms of disease and must always be considered if no firm diagnosis has been made. Bronchitis, pneumonia, smoker's lung and lung cancer can all show practically the same symptoms as lung tuberculosis.
If tuberculosis is suspected, tests will need to be done to rule out the presence of these other diseases. Examination of sputum will usually include a check for cancer if the chest X-ray raises any suspicion of this type of diagnosis.
Non-Lung TB can be confused with cancers, it can be a cause of a wide range of gastro-intestinal symptoms, infertility and unusual skin lesions.
Other non-tuberculous mycobacteria found in soil and water can cause disease in susceptible patients with a history of cystic fibrosis, chronic lung damage, alcoholism and immunosuppression (suppression of immune responses by a disease or drugs).
These atypical mycobacteria can be present as colonising organisms without necessarily causing disease.
When should I see a doctor?
If you have a persistent cough with sputum for more than three weeks or you see blood in your sputum or unexplained weight loss or unexplained night sweats, you should your doctor.
For lung TB, the doctor cannot always hear enough to make a diagnosis by just using a stethoscope. If your physician suspects there is something wrong and that it is not just a cold, you may be referred to an outpatient department for people with lung diseases or to an X-ray department.
The chest X-ray examination is the most important test. If there are changes in the lungs, a sample of sputum will be sent for microscopic examination and culture. Culture of tuberculosis bacteria will take 4 to 12 weeks. For this reason, it takes some time before an accurate diagnosis is possible.
Quicker methods using DNA techniques are now available, and a skin reaction Mantoux test can sometimes be a great help. In this test, Tuberculin, which is a substance extracted from the tubercle bacteria, is injected into the skin.
If the skin shows a strong reaction after 72 hours, it means there is hypersensitivity to tuberculin protein acquired either by a previous BCG vaccination, or possibly due to an active infection.
With non-lung TB, the diagnosis may only be made after surgical exploration. In both lung and non-lung TB, we now have blood tests that can tell if you are on of the two-thirds in the world never infected (a negative test).
If the test is positive you either have active TB (which may be infective to others) or you have latent TB (which may become active if your immune system is made less effective by steroids, age or HIV).
How to be vaccinated against tuberculosis
In the UK, BCG vaccination (with live but weakened tubercle bacteria) is no longer routinely given to all children of secondary school age.
The highest rates of the disease occur in particular risk groups and it now makes more sense to target BCG vaccination for people who are at greatest risk of the disease.
The vaccine is now recommended for:
✔️ Infants under one year of age living in areas where the incidence of TB is 40 cases per 100,000 people or higher (technically this applies to London, UK).
✔️ Infants under one year of age whose parents or grandparents were born in a country with an incidence of TB of 40 cases per 100,000 people or higher.
✔️ Children with risk factors for TB who have not previously been vaccinated.
✔️ New immigrants from countries with a high incidence of TB who have not already been vaccinated.
✔️ Contacts of people diagnosed with TB affecting the lungs.
✔️ Health care workers, veterinary staff, staff working in prisons, residential homes, shelters for the homeless or hostels for refugees.
✔️ People intending to live, travel or work in countries with a high incidence of TB for more than a month.
Vaccination is thought to reduce the likelihood of subsequent pulmonary TB and effectively prevents varieties of blood-borne tuberculosis such as miliary TB or tuberculosis meningitis in infants, which can be difficult to diagnose in time and can cause devastating damage.
How is tuberculosis treated?
Today, treatment for uncomplicated cases involves three or four different kinds of antibiotics given in combination over six to nine months. Multiple medicines are necessary to prevent the emergence of resistance, which would lead to treatment failure and the nightmare of multiple drug-resistant organisms.
Single medicines must never be added to a failing treatment regime. Therapy should be directed by a chest physician who will have specialist knowledge of the complications and side-effects of TB medicines.
Attention to the details of treatment are vital. The main cause of treatment failure is non-compliance with what is perceived as a demanding and prolonged programme of therapy. Those patients who are microscopy or smear positive are infectious and, if possible, should avoid with other people for two weeks.
Patients do not require hospital admission in order to start treatment. Other patients with a lower bacterial load are smear negative but culture positive on testing. These patients are not as infectious but should still have therapy along conventional lines.
Chemoprophylaxis with a single medicine, isoniazid, may be given for 6 to 12 months with the aim of preventing future disease in individuals who show no evidence of disease, but have a strongly positive tuberculin skin test and no evidence of previous BCG vaccine to explain the positive skin test.
Pregnant women with TB must be treated urgently as the disease may progress rapidly with high risk to both mother and baby.
HIV/AIDS and tuberculosis
Yes. In certain African countries and many parts of Southeast Asia, HIV is becoming more and more endemic.
Where tuberculosis is also endemic among the population, a weakened immune system will increase the risk of getting tuberculosis.
This is an extremely worrying situation and the WHO and the IUATLD are doing all they can to prevent the disease from spreading.
Can tuberculosis be prevented?
TB is reduced with better housing and less over-crowding. The most important step is to find, isolate and treat all disease carriers until they are no longer an infective risk to others. It is always advisable not to get too close to people who are coughing; equally, people with a cough should be aware of those around them and try not to cough or spit near them.
If you travel in countries where tuberculosis is a problem, get travel health advice about BCG vaccination and avoid socialising with people who have a persistent cough. Make sure that you eat well and enjoy plenty of sunlight and exercise.
Seek medical attention:
- If you develop a cough that persists for more than three weeks
- If you see blood in your sputum
- If you have unexplained weight loss or unexplained night sweats