Tuberculosis (TB)

Tuberculosis, usually shortened to TB, is an infection caused by a bacterium called Mycobacterium tuberculosis. It most often settles in the lungs, and although it can be serious if it isn't treated, it can be cured with antibiotics.

What are the symptoms of tuberculosis?

TB symptoms usually come on slowly rather than suddenly, which is part of why the infection can go unnoticed for a while.

The main sign of TB in the lungs is a cough that lasts more than three weeks and usually brings up phlegm, which may have blood in it.

TB can affect other parts of your body too, including your glands, your bones and your nervous system. When it does, the symptoms depend on which part is affected.

Some people have the infection with no symptoms at all. This is called latent TB, and it's covered in the section on types below.

None of these symptoms points only to TB. They all have other possible causes, which is why testing matters.

What causes tuberculosis and who is at risk?

TB passes from person to person through the air. When someone with TB in their lungs coughs, sneezes or spits, they release tiny droplets carrying the bacteria.

You only need to breathe in a few of those germs to become infected. That said, catching TB usually takes close, prolonged contact rather than a passing encounter.

Only people with active TB in their lungs can pass it on. Someone with latent TB cannot infect anyone else.

TB is more likely to take hold if your immune system isn't working well. The NHS offers the BCG vaccine to groups considered at higher risk, which gives a sense of who those groups are:

• babies living in parts of the UK where TB is more common
• babies and children living with someone who has TB
• babies and children born in, or who have lived in, a country where TB is more common
• babies and children whose parents or grandparents were born in a country where TB is more common
• people spending more than three months in a country where TB is more common
• people at risk through their work, such as healthcare workers who look after people with TB.

Are there different types of tuberculosis?

TB is grouped in two ways. The first is whether the infection is active or dormant.

• Active TB means you have symptoms and, if the infection is in your lungs, you can pass it to other people.
• Latent TB means you carry the bacteria but they're being held in check by your immune system. You have no symptoms, you don't feel ill, and you can't infect anyone. The bacteria are still alive though, and the infection can become active later.

Latent TB is far more common than most people realise. The World Health Organization estimates that around a third of the world's population carries it.

The second way TB is grouped is by where in the body it sits.

• Pulmonary TB is TB in the lungs, which is the most common form.
• Extrapulmonary TB is TB anywhere else, including the glands, the bones and the nervous system.

How is tuberculosis diagnosed?

If your GP thinks you may have TB, they'll usually refer you to a TB specialist for testing and treatment.

Tests can include:

• a Mantoux test, where a small amount of liquid is injected under the skin of your arm. If you have the TB bacteria, your skin reacts at the injection site
• blood tests
• imaging of your chest, or of whichever part of your body may be affected. This might be an X-ray, an ultrasound, a CT scan or an echocardiogram
• a biopsy, where a small sample of tissue or fluid is taken from the affected area and tested for the bacteria.

If you have no symptoms but you're at risk, for example because you've been in close contact with someone who has TB, you may be offered a Mantoux test or blood tests to check whether you've picked up the infection.

How is tuberculosis treated?

The main treatment is antibiotics. TB is curable, and most people don't need to be admitted to hospital for it.

Active TB

You'll usually take antibiotics for at least six months.

If TB has spread to your brain, your spinal cord or the area around your heart, you may also be given a steroid medicine for a few weeks alongside the antibiotics.

Latent TB

If you have the infection but no symptoms, you'll usually take antibiotics for three to six months to clear it before it has the chance to become active.

Latent TB isn't always treated if the strain is thought to be resistant to the usual antibiotics. In that case you may be monitored regularly instead, to check that the infection stays dormant.

Finishing the course

This is the part that matters most. Take your antibiotics exactly as prescribed, and keep taking them until the course is finished, even once you feel completely well.

Stopping early or skipping doses gives the bacteria a chance to become resistant to the antibiotics. If that happens, the infection can come back and it becomes much harder to treat.

When should I see a doctor?

See your GP if you have a cough that has lasted more than three weeks, particularly if you're coughing up phlegm or blood.

Also make an appointment if:

• you've been in close contact with someone who has active TB, even if you feel completely well
• you have symptoms that have been building slowly over weeks rather than days
• you're about to start a medicine that suppresses your immune system, as you may need TB screening first

Don't turn down TB screening because you've had the BCG vaccine or because you feel fine. The point of screening is to find infection in people without symptoms.