Biological Risk and Prevention of Tuberculosis

Dear Colleagues,

Tuberculosis (TB) is very common in the general population; it spreads by air, so it is highly contagious. The diagnosis of it is often difficult, the prevalence of latent forms is very high, and some maneuvers that are commonly practiced in hospitals increase the risk of contagion (e.g., cough induction, bronchoscopy, or spirometry). The treatment of an active infection is lengthy, and there are numerous drug-resistant forms. Furthermore, vaccination is considered to be scarcely effective in preventing contagion. TB affects about 2 billion people worldwide, one-third of the world's population hosts the mycobacterium in a latency state, and about 10 million new infections are recorded every year.

The average risk of contagion Is about 22% for each significant contact, but this percentage is highly variable in relation to some characteristics of an exposure episode, such as the number of mycobacteria that a subject emits into the environment by coughing, the position as well as efficacy of ventilation, and host susceptibility. Most immunocompetent people do not develop an infection, which can occur, on average, in 22% of subjects. After this initial contagion, a small minority of patients develop an active infection, around 5%, while the vast majority develop a form of so-called latent infection, which, however, can undergo reactivation over the course of a subject's life, on average in 10% of cases. Half of these reactivations occur within the first 2–5 years after exposure. Specific anti-TB therapy is very effective in reducing a patient's contagiousness to a negligible level already after two weeks of treatment; therefore, the ideal would be to achieve a very early diagnosis to interrupt the chain of contagion. However, this early diagnosis remains very difficult due to a series of factors: the long latency of an infection, which can reach up to 20 weeks from the moment of infection, the presence of poorly symptomatic or even asymptomatic pulmonary forms, and the presence of increasingly frequent extrapulmonary forms of cutaneous, ocular, or renal TB.

There are multiple options for the treatment of latent infection, the most common option being treatment with isoniazid (INH) for a shorter or longer period. The only vaccine currently available against TB is the live-attenuated BCG vaccine (bacillus Calmette Guérin), which is effective in the prevention of severe childhood forms of the disease (meningitis and other forms of disseminated TB in infants and children). The vaccine is often used in young children in countries with a high incidence of TB. In Italy, the vaccine is only used in some risk categories. Numerous trials are currently underway to search for more effective vaccines.

This Special Issue would update the treatments of and programs for the prevention of TB.

Potential topics include, but are not limited to, the following:

• Role of vaccines in medicine;
• Innovative techniques to improve the programs of prevention;
• Mechanisms of action of TB;
• New methods with which to prevent TB;
• New models of the etiopathogenesis of TB;
• Association between exposure to risk factors and the onset of TB.

Prof. Dr. Venerando Antonio Rapisarda
Dr. Veronica Filetti
Dr. Ermanno Vitale
Guest Editors

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• tuberculosis
• prevention
• vaccines