When a person with infectious TB coughs or sneezes, droplet nuclei containing M. If another person inhales air containing these droplet nuclei, he or she may become infected. However, not everyone infected with TB bacteria becomes sick.
Persons with latent TB infection do not feel sick and do not have any symptoms. They are infected with M. The only sign of TB infection is a positive reaction to the tuberculin skin test or TB blood test.
Persons with latent TB infection are not infectious and cannot spread TB infection to others. About half of those people who develop TB will do so within the first two years of infection. The good news is that latent TB can be treated to prevent this happening. Very few people fall ill immediately after they breathe in TB bacteria. If it is unable to do this, it may be able to stop you from becoming ill by forcing the bacteria into a latent sleeping state.
The bacteria are still in your body, but they are not causing damage. Latent or active TB In most healthy people, the immune system is able to destroy the bacteria that cause TB.
Who's most at risk? Anyone can get TB, but those at greatest risk include people: who live in, come from, or have spent time in a country or area with high levels of TB] — around 3 in every 4 TB cases in the UK affect people born outside the UK in prolonged close contact with someone who's infected living in crowded conditions with a condition that weakens their immune system, such as diabetes having treatments that weaken the immune system, such as chemotherapy or biological agents who are very young or very old — the immune systems of people who are young or elderly tend to be weaker than those of healthy adults in poor health or with a poor diet because of lifestyle and other problems, such as drug misuse , alcohol misuse , or homelessness Page last reviewed: 12 November Next review due: 12 November In primary TB disease recent infection , some young children can show infiltration on chest radiographs suggesting active TB, but this manifestation is frequently spontaneously resolved leaving calcified scar lesions.
In contrast, reactivation of latent TB caused by a weakened immune status and presenting as cavities in the lung apex or superior segment of the lower lobe is known as secondary TB disease remote infection.
However, according to recent reports, different presentations of primary TB disease, which shows pulmonary infiltration at the lower lobe, and secondary TB disease, which presents as pulmonary cavities in the apex or superior segment, seem to be related to the host's immune status rather than time It seems that active TB generally develops within a year after LTBI, and the rate of active TB cases decreases sharply after the first year and continues to decrease slowly thereafter in the following 10 years There is a subclinical borderline phase with uncertain radiological manifestations prior to symptomatic presentation In this obscure subclinical phase, which can last for months between latent and active clinical TB, molecular diagnostic methods or computerized tomography scans can be used to prevent infectious TB from going unnoticed 27 , but cost-effectiveness must also be considered.
However, treatment interruption and overtreatment for unnecessary candidates must be avoided. In other words, shorter treatments with fewer adverse events must be performed and the number of candidates needed to be treated for preventing one additional active TB progression from latent TB must be minimized by mutual agreement between policymakers and clinicians TB can be transmitted by respiratory droplet nuclei.
The factors that influence the transmission of TB bacilli are the strength of the infectious source, infectiousness of virulent TB bacilli, immunoresistance of the host, environmental stresses, and biosocial factors. Infection controls to reduce TB transmission consist of national and subnational activities, which include managerial activities, administrative control, engineering control, environmental control, and personal protective equipment provision, in health-care facilities, congregate settings, and households, respectively.
To reduce the TB prevalence rate, the range of candidates for LTBI treatment, including those in the high-risk group, needs to be expanded. However, consensus between clinical and public aspects must be achieved based on definite domestic evidences.
Conflicts of Interest: No potential conflict of interest relevant to this article was reported. National Center for Biotechnology Information , U. Tuberc Respir Dis Seoul. Published online Oct 5. Seung Heon Lee , M. Find articles by Seung Heon Lee. Author information Article notes Copyright and License information Disclaimer.
Corresponding author. Address for correspondence: Seung Heon Lee, M. Phone: , Fax: , rk. All rights reserved. This article has been cited by other articles in PMC. Introduction Tuberculosis TB is an infectious disease that has existed throughout human history. Transmission of TB TB bacilli can be transmitted as droplet nuclei that are residues of dried respiratory droplets. Open in a separate window. Figure 1. Schematic presentation of factors determining the likelihood of transmitting tuberculosis TB infection 8.
Mathematical Models of Transmission The most representative quantitative study for airborne infection through droplet nuclei is the school measles outbreak study. TB Outbreaks and Infection Control Recently, TB outbreaks have been reported frequently in middle and high schools, military locations, work places, and dormitory settings in South Korea Table 1 Activities to reduce the transmission of TB Clinical Perspective of the Infectiousness of TB Patients with pulmonary, laryngeal, or endobronchial TB are highly contagious, and the infectiousness is increased in the following conditions: 1 presence of lung cavities, 2 positive acid-fast bacillus smear or culture for sputum, and 3 presence of respiratory symptoms like cough.
Table 2 Guidelines for estimating the beginning of the infectious period of TB patients according to index characteristics Characteristic Recommended minimum beginning of likely period of infectiousness TB symptoms AFB sputum smear positive Cavitary chest radiograph Yes No No 3 Months before symptom onset or first positive finding e.
TB: tuberculosis; AFB: acid-fast bacilli. Figure 2. Conclusion TB can be transmitted by respiratory droplet nuclei. Footnotes Conflicts of Interest: No potential conflict of interest relevant to this article was reported.
References 1.
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