It is said that "there is no better treatment than prevention," but what prevention strategies are available for tuberculosis (TB)? We will consider methods in these three categories.
When there is a high risk of infection
BCG vaccine (vaccination)
BCG is a vaccine that confers resistance (immunity) against TB in uninfected individuals by injecting a person with an innocuous relative of the tuberculosis bacteria Mycobacterium tuberculosis. In Japan, children receive the BCG vaccine before reaching one year of age (ideally at 5-7 months of age). The method of vaccination is a "stamp" injection, which results in 18 small needle marks that appear roughly 6 months after inoculation.
Vaccinated individuals have an 80% lower chance of developing the disease after infection compared to those who are unvaccinated. In infants, TB infections entail a substantial likelihood of severe illnesses such as meningitis, and the BCG vaccine is effective in preventing these outcomes as well.
The vaccine is thought to remain effective for 10-15 years.
Treatment of latent TB infection (chemoprophylaxis)
Those who have recently been infected with the Mycobacterium tuberculosis bacterium have a high risk of developing TB within one to two years. Even those who were infected less recently may suffer from a heightened risk of developing TB due to a number of causes (see Tuberculosis symptoms). Drugs that suppress the immune response, which are taken during treatment for numerous diseases, are particularly problematic if you are infected with TB. This state is known as a latent tuberculosis infection, with the Mycobacterium tuberculosis bacteria in the body considered to be in a preparatory stage prior to disease onset. Patients at this stage of infection are asked to take a course of TB treatment to kill off the bacteria before they trigger the active disease. This prophylactic treatment was formerly known as chemoprophylaxis, or preventive internal administration, and is thought to reduce the risk of disease onset by about 50-80%.
The tuberculin reaction test is used to diagnose latent TB in infants, and a blood test (QuantiFERON or T-SPOT) is used in older patients.
The standard treatment regimen is 6-9 months of isoniazid treatment.
If someone is suffering from TB, and especially if that person is releasing Mycobacterium tuberculosis bacteria (i.e., infectious tuberculosis), there is a risk that the bacteria may have infected those nearby. Moreover, if the person showing symptoms of the disease is a child or adolescent, they may have recently acquired the infection from someone else. Therefore, when a person is found to have TB, it is necessary to find those who are also infected or are the source of the infection. The search for and examination of such people is known as a contact investigation, and is an important part of the TB control measures carried out by public health centers. If not done properly, the situation may worsen and lead to mass outbreaks or grave illnesses in infants.
Characteristics of an initial patient indicating that a contact investigation is especially important
- 1Patient is releasing large amounts of bacteria (positive smear test)
- 2Patient has not been diagnosed in a long time
- 3Patient is a child or adolescent (especially in the case of multiple patients)
- 4Patient has a rare disease type (e.g., meningitis, middle ear infection, etc.)
Characteristics of a contacted person that indicate a contact investigation is especially important
- 1Person is an infant or has reduced immune function due to illness (e.g., AIDS or kidney failure) or treatment (e.g., adrenocortical hormone therapy)
- 2Person has been in close contact with the initial patient (e.g., family members or close friends)
Tests and evaluations that are part of a medical exam
- 1Evaluation: Assess the extent to which the person under examination has talked with or worked or studied in the same room with the patient since the onset of the illness (the onset of coughing). Possible situations where contact may have occurred include family life, workplace/school activities, clubs, hobbies, and leisure activities.
- 2Blood test (QuantiFERON or T-SPOT)/immunodiagnostic tuberculin reaction test: These tests check for TB infection. If it is judged that an infection has occurred, it is necessary to treat the latent TB infection (chemoprophylaxis).
- 3Chest X-ray exam: Determine whether an infection has already triggered disease onset. Patients with early-stage TB are most often asymptomatic, and early discovery and treatment is key. For those with high infection risks, this test should be administered repeatedly for about two years after the time when contact with the first patient occurred.
Tuberculosis is an important public health issue
In Japan, the Infectious Diseases Control Law stipulates various measures for controlling TB.
The following are some measures that relate to TB control in Japan.
- BCG vaccination
The government is required by law to work towards the vaccination of all infants. In recent years, nationwide vaccination rates in Japan have reached over 97%.
- Treatment of a latent TB Infection
Although only young patients were treated in the past, treatment is now performed on patients of all ages. As with standard TB treatments, in Japan, the cost is covered by public funding.
- Patient discovery
Patient discovery may occur during a health checkup or may be triggered by the onset of symptoms. Contact investigations (non-periodic health examinations) occur when medical exams are conducted on those in the vicinity of infected persons in an attempt to find others who may be infected or be experiencing the disease. A breakdown of recent methods for discovering pulmonary tuberculosis patients is as follows (Fig. 9).
- Patient Support
Although only young patients were treated in the past, treatment is now performed on patients of all ages. As with standard TB treatments, in Japan the cost is covered by public funding.
- Public aid
In Japan, TB treatment is subsidized through public health insurance as well as through public funds. This prevents situations where a course of treatment may need to be ended prematurely due to the patient's financial situation, and also makes the government responsible for treatment quality.
- The Japanese version of DOTS
To ensure that a patient completes his or her treatment in accordance with the doctor's instructions, a patient's doctor coordinates with health centers during the entire duration of the hospitalization/outpatient treatment regimen to help ensure the patient receives the proper treatment.
In-hospital quarantine is recommended for patients who are at risk of spreading the disease to others.
- Public aid
- Surveillance (trend monitoring)
Data collection and analysis is carried out continually to determine trends in TB outbreaks and evaluate countermeasures/medical treatments. This information is used to plan further actions.
- The Japan Anti-Tuberculosis Association and the Stop TB Partnership Japan
The Stop TB Partnership Japan was established in November 2007 in cooperation with both public and private sector organizations including the Japan Anti-Tuberculosis Association. The organization serves as a vehicle for maintaining and strengthening coordination in the fight against TB both in Japan and worldwide.