Latent tuberculosis (TB infection): testing, treatment and what it means

Tuberculosis (TB) is caused by bacteria and usually affects the lungs. The NHS says that some people have TB in their body but do not get ill or have any symptoms, and this is called latent TB. If you have TB and you have symptoms, it is called active TB. University Hospitals Plymouth describes latent TB as TB bacteria living quietly in your body: you are not ill and you cannot pass TB on to others, although the bacteria might become active in the future, making you ill with TB disease.

The NHS says latent TB cannot be spread to others but it can turn into active TB in the future. That possibility is why it is treated, even though you feel well.

The NHS says anyone can get TB, but some people are more likely to get it or get more seriously ill from it. It lists people who spend a lot of time with someone who has active TB, such as living in the same home, were born in or lived in an area where TB is more common, have a weakened immune system such as people with HIV, diabetes, a kidney transplant or on chemotherapy or biologic medicines, are under 5 years of age, are homeless, live in prison or a detention centre, regularly smoke, drink alcohol or take drugs, or have had TB before that was not treated properly.

TB spreads through close contact with people who have active TB and symptoms, when droplets released by coughing are breathed in regularly over a long period of time.

There are no symptoms, so latent TB is found by testing people who are at risk. The NHS says if you have no symptoms but are at risk, for example because you have been in close contact with someone who has TB, you may have a Mantoux test or blood tests to check if you have it. A Mantoux test is a skin test where a small amount of liquid is injected under the skin in your arm, which causes a small reaction on your skin if you have TB.

The NHS lists X-ray or other scans, samples of mucus you cough up, and biopsy among the tests used when someone has symptoms and may have active TB.

The NHS says if you have latent TB you usually need to take antibiotics for 3 to 6 months, and that it is important to take them correctly and complete the course even if you feel well, because TB could come back if you stop early. The Plymouth leaflet says you may be given rifampicin and isoniazid for three months, likely together in a tablet called Rifinah, or isoniazid by itself for six months, or rifampicin by itself for four months. A TB specialist nurse explains the treatment.

The Plymouth leaflet says if you complete your treatment, your risk of developing TB disease is much lower, but there is a small chance you could breathe in TB bacteria again in the future. It is useful to know the most common symptoms so you can see a doctor quickly: a cough that lasts for three weeks or longer, fever, night sweats, weight loss, no appetite and tiredness. The NHS adds that you should see a GP if you have had a cough for more than 3 weeks, feel tired all the time for no reason, have a high temperature or night sweats that do not go away, or keep losing weight without trying.

The NHS says to ask for an urgent GP appointment or get help from NHS 111 if you are coughing up blood, and to call 999 or go to A&E if you have a stiff neck and severe headache, pain on looking at bright lights, a seizure, sudden confusion or weakness, as these could be signs that TB has spread to the brain.

The NHS says there is a vaccine for TB called the BCG vaccine, recommended for some people at higher risk, including babies who live in areas of the UK where TB is more common or who live with someone with TB, babies and children born or living in a country where TB is more common, people aged 35 and under spending more than 3 months in a country where TB is more common, and some healthcare workers. The Plymouth leaflet notes that BCG does not completely prevent TB infection or disease.

The Plymouth leaflet describes a TB specialist nurse team explaining treatment, and latent TB treatment is generally provided through NHS TB services rather than privately. If you are told you have been in contact with TB, or are applying for work or travel that requires screening, ask your GP or the TB service how to get tested.