Читать книгу Tuberculosis and War - Группа авторов - Страница 41

M. tuberculosis is mainly transmitted by the airborne route and remains the chief mycobacterial pathogen; M. bovis seems to have played a very minor role in wartime-associated TB resurgences. M. tuberculosis is most likely transmitted where population density is high and thus opportunity for exposure is increased. Transmission is much more likely to occur indoors than outdoors where tubercle bacilli are rapidly dispersed in the ambient air. Thus, where the climate is cold, people collect indoors, and poverty forces crowded living conditions that facilitate transmission. The latter situations are typically enhanced during wartime, and the tuberculin skin test surveys among children in Lebanon during the civil war discussed above may thus make a case in point. Airborne transmission of M. tuberculosis takes center stage in the pathogenetic sequence of TB (Fig. 1). Because increased transmission has long-term implications due to the open-ended incubation period of TB, it provides a key to better understand the epidemiology of TB in general and during wartime specifically. However, there are serious methodological barriers to ascertain transmission and there is scarcity of information about it.

We have alluded to factors that may increase the risk of progression from latent infection with M. tuberculosis to TB, yet have refrained from a comprehensive discussion that has been the focus of more general discussions of the epidemiologic basis of TB control [3, 79, 80]. Risk factors for progression from latent infection with M. tuberculosis to TB as they pertain in particular to periods of war will be addressed in chapter 3. We have at length tried to determine whether case fatality or faster speed at which untreated TB progresses to death is changed during war times, but have not been able to determine this in a satisfactory manner.

Finally, at the outset we have put the importance of data accuracy above all. It is always difficult to be sure about the numerator and the denominator, and this is particularly compounded during civil strife, armed conflict, and war. Data reported during such times will thus always have to be viewed with great reservation.