Contact tracing – what does it mean?

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Tuberculosis is a generally hazardous communicable disease. It must not spread. The Communicable Diseases Act stipulates that health authorities must prevent the spread of tuberculosis among the population. This is done through contact tracing. Contact tracing is initiated at the hospital and continues in a health center. Doctors in charge of infectious diseases in the municipality and hospital district monitor the results of contact tracing and, if necessary, expand the measures.

The aim of contact racing is to identify other people with the disease, as well as those infected who would benefit from preventive treatment. In addition, when a child or young adult becomes ill, the source of the infection is traced.

How is contact tracing done?

Most commonly, contact tracing is initiated when a patient is diagnosed with TB disease of the lungs.

TB contact tracing measures are designed according to the infectiousness of the disease.

The duration of the infectious period depends on how long the patient has had respiratory symptoms and how extensive the changes found in the chest x-ray are. The period of infectiousness can range from a few weeks to over a year. It is usually about three months.

According to the Communicable Diseases Act (§22), the person who has become ill must disclose the names of persons who may have been the source of the infection or who may have become infected. Health personnel in the hospital will interview the patient to find out who may have been exposed. Their names and contact details are gathered. Exposed people are individuals with whom the patient has had a lot of contact during the infectious period.

  • Family members and other people living in the same household as the person with TB disease
  • other people and groups such as friends, relatives and people at work, at school and in any hobby circles

By giving the names of these people the person with TB disease helps others stay healthy. The given information is confidential. The name of the patient is not revealed to those who are invited for evaluation.

It is not necessary to examine all those exposed. Family members are always examined. For others, the need for evaluation is assessed on a case to case basis depending on the exposure time indoors.

People invited for evaluation:


  • Family members and other people living in the same household as the person with TB disease. Family members may also include grandparents or other loved ones who have a lot of contact with the family. Children under the age of 7 will be examined as soon as possible. Unvaccinated children under the age of 5 have the highest risk of developing TB disease after a possible infection. They can also develop severe forms of tuberculosis.

In addition

  • If the risk for transmission is high these individuals outside of the family will be examined: those under the age of 7 who have been exposed for at least 8 hours and those over the age of 7 who have been exposed for at least 40 hours.

If the risk of transmission is low, only children outside the family under the age of 7 who have been exposed for at least 40 hours are examined.

Medical procedures performed on the person with TB disease during the infectious period are investigated and it is assessed whether there was an event (e.g. surgery) or risk procedure (e.g. bronchoscopy, resuscitation, intubation, induced sputum sampling, airway suction, obduction, spirometry and dental treatment) that would have exposed the worker to TB bacteria.

How is information about those exposed transferred?

The names and contact information of the exposed persons are recorded in the hospital on contact tracing forms and sent to the infectious disease doctor at the health centre of the place of residence. Those exposed at the workplace are reported in the same way to the occupational health service.

Where will those exposed be examined and what examinations will be carried out?

The arrangements for evaluation vary from municipality to municipality. In general, a letter is sent from the hospital or health center to the exposed person, together with a questionnaire and the exposed person is asked to book an appointment or telephone call to the health center or occupational health service.

Examinations for adults are usually carried out at a health center. Children under school-age and people with a medical condition or taking medication which increases the risk of developing active TB disease are examined at the hospital.

All exposed persons have a chest X-ray and are given TB information. Further investigations will be arranged as soon as possible for those with symptoms of TB.

For people under 35 years of age, a blood test (IGRA, B-TbIFNg) is performed two months after the last exposure. The test will tell whether the body has been exposed to TB bacterium. In healthy individuals exposed to TB, a value of ≥ 1 IU/ml is considered an indication of TB infection.  These individuals may be given preventive drug treatment (LTBI treatment). The test cannot predict who will develop TB disease. The assessment and decision on treatment is made in specialized care in the hospital.

Why is the IGRA test not done on everyone exposed?

The IGRA test is performed on those who are scheduled to receive preventive drug treatment.

Drug treatment is not recommended for people over 35 years of age, as they are more likely to develop hepatitis associated with drug treatment than younger people. However, treatment is given if someone over the age of 35 has another illness or medication that increases the risk of TB infection progressing to TB disease. In this case, the potential harm of LTBI treatment is acceptable.

Why is the threshold for a healthy exposed person’s IGRA test result leading to treatment of LTBI 1.0, when the laboratory considers a result of 0.35 to be positive?

A negative test result (<0.35) reliably rules out TB infection in a healthy exposed person. Interpreting a positive test result is more difficult. It is known that results close to the test manufacturer’s limit value are highly variable for many reasons. False positive results are therefore possible. Studies have shown an increased risk of developing TB disease in the range of 1.0-4.0.

In Finland, a team of TB experts has come to this recommendation in order to target the treatment of LTBI (latent tuberculosis infection) with greater certainty at people who are actually infected with tuberculosis and thus benefit from the treatment. For persons at increased risk of developing TB disease (illnesses and drug treatments which weaken the immune system), the cut-off for a positive test result is 0.35.

What is LTBI treatment?

Drug treatment of LTBI can prevent the development of TB disease in the majority of those treated. Treatment involves the use of 1-2 anti-TB drugs. Treatment usually lasts for 3 months (two drugs) or 6-9 months (one drug).

Treatment decisions are based on individual assessment and discussion. Treatment is only given if the person is willing and committed to treatment. The decision to treat is substantially influenced by an individual assessment of the risk of treatment-related adverse effects. Treatment is initiated and monitored in specialist care and is free of charge for the patient.

Click here to read more about the patient information leaflet.

Who will need follow-up x-rays?

Follow up chest X-rays are repeated after one year only in the following cases:

  • the exposed person is over 35 years of age and a family member or has participated in a risk procedure
  • a person who has been diagnosed with LTBI but for one reason or another has been unable to receive treatment. If a person has been exposed to drug-resistant TB or has a substance abuse problem, their condition will be monitored by chest x-ray for two years.

How much do the tests cost?

All tests and treatments due to TB exposure are free of charge for the person under the Act on Social and Health Care Client Fees. The actual cost of outpatient visits, examinations and medication is around € 1,400.

What else should the person who has been traced remember?

It is important to remember that you have been exposed to TB. In the future, tell the medical staff treating you about the situation. It is possible that you get ill with TB disease decades after exposure. Contact your doctor to check the possibility of TB if you experience any of the following symptoms:

  • prolonged cough, sputum, mucus lasting more than three weeks,
  • feverishness or fever for which no explanation can be found
  • loss of appetite and unintentional weight loss
  • exceptional fatigue
  • abnormal night sweats