We will have only eight patients, and as a result we will have 8 × 2 × 5 = 80,only 80 new infections. After the cycle we will have only. 64 infections' and then 51, 41, 33 etc.
In this way the extent of epidemics will diminish gradually under the reduced value of any of the parameters. On the contrary, the TB situation will be deteriorated, if something happens to increase the value of any of the parameters. Apparent improvement or worsening of the situation as seen in the history of tuberculosis in many countries during the progress of industria1 revolution, wars or economic development may be the consequences of the readjustment of the parameter values in those ways as illustrated as above.
b) Interventions with Control Measures
Then, the tuberculosis control is understood as something to reduce the parameter values so that the size of epidemics be shrunken.
Let us consider what measures should be used, and how they are effective for that purpose. The risk of clinical breakdown may be reduced with use of BCG vaccination.
However, the BCG vaccination is considered to be effective only for preventing children tuberculosis that is virtually noninfectious.
Therefore, BCG vaccination cannot reduce the risk of breakdown of the population as a whole substantially. Another measure, the chemoprophylaxis for the infected persons could be used. However, due to operational difficulties, it is never practiced in the developing world.
The second parameter, the duration of disease, may be reduced by detecting the patient as early as ppossible after the onset. At the same time the detected patients have to be treated adequately so that they do not discharge bacilli any longer.
This is why good case-finding programme should be combined with good treatment programme ,as sometimes called as“Case-finding & Treatment complex.”
This combination is considered as an only measure to cut the chain of TB epidemics, and WHO determined the target of global TB storage as in Table 3.
Table 3 Targets for Global TB control (WHO)to cure 85% of the new smear positive TB cases, and to detect 70% of exciting cases by the year 2000.
NB Do not produce MDR TB by giving priority to case-finding before achieving good treatment programme.
The effectiveness of treatment is measured in teams of the speed of bacteriological conversion after the start of the treatment for a cohort, i.e. a group of patients having started treatment during a certain period.
However, we have to consider the persons who stop taking drug prematurely, or take drugs irregularly, and also persons who fail to react favorably to the treatment.
Many of these patients may continue spreading bacilli and become dangerous sources of infection in the future. The more serious problem is their bacilli are resistant to one or more anti-tuberculosis drugs. These cases are called as chronic excretors.
They are harmful not only to themselves, but to the society. Once a person is infected with this resistant stain of the bacilli, and develops TB, then his TB cannot be cured with ordinary regimens. Therefore it is even possible that the poor treatment programme with high failure and defaulter rates may be harmful than nothing, by producing resistant cases spreading bacilli for a longer period. This is why WHO claims 85% cure rate as a minimum target for a treatment programme.
3. Treatment Programme and TB Control Policy Package
Considering the utmost important of the treatment regularity in the treatment, I would like to put separately another activity as one of the measures to shorten the disease duration; Case-holding. Case-holding is a set of services to ensure the regular drug taking by the patients, including the health education or motivation of the patients, home visit of the defaulting cases, supervision of drug-taking and so on.
Nothing specific may be discussed under the measures for reducing infectivity, because prevention of infection is inherent with the case-finding and treatment“Isolation” of infection is inherent with the case-finding and treatment “Isolation of the patient mat be one of them, but under the cover of the current powerful chemotheraphy, physical isolation of the sources of infection from the society has little additional meaning over the effect of chemotherapy “chemical isolation.”
In order for the case-finding and treatment programme to be effective enough, they have to be supported by several components.
All these components are incorporated into a National Tuberculosis Control Programme.
In the light of its most effective and efficient implementation, WHO has recently announced the “TB” Control Policy Package, defining five critical elements to be included in the NTP as shown in Table 4.
Table 4 WHO TB Control policy Package
1) Government commitment to a TB control programme
2) Case detection through predominantly passive case finding
3) Administration of standardized SCC to -at least- all sputum smear positive cases under proper case management conditions
4) Establishment of a system of regular drug supply
5) Establishment and maintenance of a monitoring system
In order to implement the above Package, WHO specifies the actions under
