Contact tracing

Latent TB infection and TB disease

An infected person may have TB bacteria in his or her body without it making the person ill. This is called latent tuberculosis infection (LTBI). The bacteria are sleeping. The person has no symptoms, is not ill and cannot spread the disease to others. This can continue throughout the person’s lifetime.

However, if the bacteria become active and begin to multiply in the body, the person gets ill with TB disease. He or she will usually have symptoms of TB. The disease can also spread to others. Only a small portion of infected people get ill. This depends on a person’s immune system and age. People with less than 5 years of age and those with a weak immune system are more likely to become ill with TB disease.


A situation where a person can become infected is called exposure. Tuberculosis is spread through the air. When a person with TB disease of the lungs or throat coughs, sneezes, speaks or sings, TB bacteria are released in the air. Anyone who is near by (room, apartment, work space, car, etc.) can breathe bacteria into their own lungs and get infected.

TB is not easily transmitted. Only a part of exposed people become infected. People living in the same household are at highest risk because they spend much time with the ill person indoors. Also those who often spend time with the ill person are at risk.

TB can only be transmitted through breathing. TB is not spread through clothes, dishes, shaking hands, surfaces the sick person has touched, or sex.

Contact tracing -what does it mean?

Why is contact tracing done?

Contact tracing is a process used to stop the spread of TB disease in the community. Contact tracing activities are regulated by the Finnish Communicable Diseases Act.

The aim of contact tracing is to find other people with TB disease and those infected with TB.

How is contact tracing conducted?

Most commonly, contact tracing is started with a patient who has been diagnosed with TB disease of the lungs.

It is possible that some other people who have spent a lot of time with the patient have been infected with TB or have got TB disease.  Health personnel in the hospital will interview the patient to find out who those people may be.

For example

  • members of the family and other people living in the same household with the person with TB disease
  • other persons and groups such as friends, relatives and persons at work or study place and in potential recreational circles

By giving the names of possibly infected persons, the person with TB disease helps others around to stay healthy. The information he/she gives is confidential.

Where are the exposed examined and what kind of tests are done?

The exposed people are contacted and asked to book a time for a checkup.

Checkup for adults is usually done in a health center. Children under school age are examined at the hospital.

Tests always include a chest x-ray and sometimes a blood test (IGRA, B-TbINFNg).

If the person has symptoms of TB disease further tests will be done urgently.

All exposed are given information about TB.

What happens if TB disease or TB infection is detected?

If TB disease is detected, medication for TB disease will be started. Read more about treatment of TB disease here.

Some of those who have latent TB infection can be offered a preventive treatment course. The decision is made by a doctor.

What is treatment for latent TB infection?

Treatment of latent tuberculosis infection can prevent the development of TB disease in the majority of those who get treatment. The person is treated with 1-2 TB medicines. The treatment usually lasts for 3 months (two medicines) or 6 months (one medicine).

The decision to treat depends on individual consideration and risk assessment (individual risk that the person gets side effects from TB medicines). Treatment is given assuming that the person is committed to it. Voluntary treatment is free of charge. Treatment is started and monitored in hospital.

Who needs follow up tests?

Some exposed people will need follow up tests for 1-2 years.

What does the checkup cost?

According to the Finnish Communicable Diseases Act, all tests and treatments that are due to exposure to TB are free of charge for the person exposed to TB.

What should you still remember?

Give your support to the person who is ill with TB during his/her treatment. Tuberculosis is nobody’s fault.

It is important that you remember that you have been exposed to TB. In the future, tell about it to health care professionals who treat you. It is possible to get ill with TB disease tens of years after exposure. Go to see a doctor if you have any of the following symptoms:

  • a cough that lasts over three weeks, coughing up sputum
  • mild fever or fever which cannot be explained
  • loss of appetite and losing weight without dieting
  • unusual tiredness
  • unusual sweating at night