Contact screening is an important strategy for control of tuberculosis (TB). Contacts are persons who are in close proximity to patients who have TB and are therefore at high risk of acquiring the infection.
- Contact: Any person who has contact with an index case with infectious TB.
- Index case: The initially identified case of TB (new or recurrent) in a person of any age in a specific household or other comparable setting in which others may have been exposed.
- Household contact: A person who shared the same enclosed living space for one or more nights or for frequent or extended periods during the day with the index case during the 3 months before starting the current treatment.
- Close contact: A person who is not in the household but shared an enclosed space, such as a social gathering place, workplace or facility, for extended periods during the day with the index case during the 3 months before commencement of the current treatment episode.
Simply put, a close contact is an individual who shared an enclosed space with a TB index case for 4 hours or more per week. This includes those living in the same household or frequent visitors to the house or contacts at work or school.
Casual contact is defined as individuals with less than 4 hours of contact per week. This may include health care workers and/or contacts at work or school.
The World Health Organization (WHO) recommends contact investigation for household and close contacts when the index case has any of the following characteristics:
- has sputum smear-positive pulmonary TB
- has multi-drug-resistant TB (MDR-TB or extremely-resistant TB (XDR-TB) (proven or suspected)
- is a person living with HIV (PLHIV) or
- is a child < 5 years of age
If the first test is negative, close contacts of patients with active pulmonary TB should undergo a second test eight weeks later.
Casual contacts of smear-negative patients are usually not evaluated unless they are immunocompromised.
Contact tracing interrupts the chain of transmission of the disease by early detection and timely and complete treatment. This reduces further transmission of the TB bacilli to others in the community. Detection of latent TB infection and its treatment prevents new “active” cases of TB.
Hence, all household and close contacts of patients with infectious TB should be traced, screened and treated with a full course of ATT if found to have TB.
Since TB is a notifiable disease, every case of TB has to be notified at nikshay.gov.in.