[Risk of travel associated tuberculosis]

Tuberculosis has spread by human movements throughout history. There have been reports indicating tuberculosis transmission on all travel vehicles, including aircrafts, ground vehicles and vessels until today. However, due to the ever increasing of air transportation and air travelling among countries with low and high tuberculosis incidence, transmission risk especially in aircrafts has become an important issue worldwide. But in many of the studies conducted in this regard, transmission of tuberculosis in aircrafts was found very low. The case of active tuberculosis has not yet been reported. This is due to the fact that in modern aircrafts, there are ventilation systems that provide hepa filtered laminar air flow and change the air 15-20 times per hour. The guidelines for the prevention of tuberculosis infection in aircrafts published by the World Health Organization "Tuberculosis and Air Travel, 2008" and European Centre for Disease Prevention and Control "RAGIDA-TB, 2014" confirm each other. According to these guidelines, air travelling of patients with active pulmonary tuberculosis should be prohibited until smears of two consecutive sputum samples become negative for drug susceptible cases, and cultures of two consecutive of sputum samples become negative for multidrug or extensively drug resistant cases. When it is reported that a tuberculosis patient has travelled by the aircraft, it is recommended that the exposed passengers should be investigated for tuberculosis infection if the flight duration equal to or exceeding eight hours including ground delays and the time elapsed between flight and diagnosis of the case is no longer than three months. Contact screening is only recommended for passengers sitting in the same row, two rows ahead and two rows behind the index case. Tuberculin skin test or interferon gamma release assay can be used for investigation. It is very difficult to determine the risk of tuberculosis transmission in ground vehicles like buses, subways and trains. The reason is that it is often not possible to access the information of the passengers travelling in these vehicles. Because the ventilation systems in ground vehicles are not as reliable as in aircrafts and the crowded environment in the ground vehicles, the risk of tuberculosis transmission is theoretically higher. In modelling studies, the transmission risk in the buses was found to be higher than the trains. In the case of regular travelling with an index case such as school bus riders, the risk increases significantly. The increased human population travelling all over the world nowadays has also raised concerns about travel-related tuberculosis risk. However, because of the limited evidence, it may be more efficient to spend time and resources for the other actions in order to prevent tuberculosis. In this review article, the transmission risk of tuberculosis in vehicles has been discussed.