Disease Control

Disease Control

The control has been defined as the reduction in the incidence, prevalence, morbidity and mortality of an infectious disease to a locally acceptable level. Disease control is an important aspect in which attempts are made to reduce the burden of disease through the application of effective measures. Every disease has the certain weak points susceptible attack. Therefore, the basic approaches to controlling disease include:

• to identify these weak points
• to break the weakest line in the chain of transmission.

For this, it requires designing of

• of effective strategies to implement targeted intervention
• competent and committed human resources for health at a various level of health care delivery
• community participation and partnerships at adifferent level
• political support
• inter-sectoral co-ordination
• resources available to implement the programs

The following are the strategiesto control the infectious diseases. It needs the combination efforts to control the reservoirs, interrupting the transmission chain, and protection of susceptible host.

Controlling the Reservoir

The elimination of animal and inanimate reservoir is easy but it is not possible in a human reservoir. The steps in controlling reservoir include:

a. Early diagnosis

There should be rapid identification of case. Laboratory diagnosis may be required to confirm the diagnosis. Early diagnosis is needed for treatment of patients, for epidemiological investigation and for the institution of prevention and control measures.

b. Notification

Once the infectious diseaseshave been detected, it should be notified to the local health authority whose responsibility is to put operation for control measures. Notification is an important source of epidemiological information as it enables early detection of disease or outbreak and permits immediate action to be taken by the health authority to control their spread.

Notification of infectious diseases is oftenmade by physicians or the head of the family but anyone including lay people (for example, religious, political and administrative leaders, teachers and others) can report even on suspicion.

c. Epidemiological investigation

The investigation cover:

• the identification of the source of infection
• factors influencing its spread in the community.

It includes:

• geographical situation
• climatic condition
• social, cultural, behavioral patterns.

d. Isolation

The separation of the case for the period of communicability of infected persons or animals from others in such places and under such conditions as to prevent o limit the direct or indirect transmission of the infection agent from those infected to those who are susceptible, or who may spread the agent to others.

There are several types of isolation:

• standard isolation
• strict isolation
• protective isolation
• high security isolation

e. Treatment

The objective of treatment is to kill the infectious agent before it is disseminated. Treatment can take the form of individual treatment or mass treatment.

f. Quarantine

quarantine has been defined as the limitation of the freedom of movement of such a well person or domestic animals exposed to communicable disease for a period of time not longer than the longest usual incubation period of the disease, in such manner as to prevent effective contact with those not so exposed. Quarantine may comprise

i. Absolute quarantine

ii. Modified quarantine

iii. Segregation

Interruption of Transmission

A major aspect of communicable disease control relates to breaking the chain of transmission. This will prevent the access of infectious agnets to the susceptible host. Food and water are the two main media for the transmission of many diseases such as typhoid, dysentery, hepatitis A, cholera etc. Clean practices such as hand washing, adequate cooking, prompt refrigeration of prepared food etc. will prevent most of the food- borne illness. Similarly, effective water treatment ranging from simple chlorination to the complex treatment will eliminate most of the water borne diseases.

In case of vector-borne diseases, control measures should be directed primarily at the vector and its breeding site. However, infections by droplet or droplet nuclei are not usually controlled effectively by attempting to interrupt their mode of spread. Control measures for such diseases depend on early diagnosis and treatment of a patient, personal hygiene, and proper handlings etc. In short, blocking the routes of transmission imply attack on environmental factors.

Protection of the Susceptible Host

Following strategies may protect the susceptible host:

a. Active immunization

One of the effective ways of strengthening the host defense is the active immunization. There are some diseases which are solely based on active immunization. Active immunization is given mostly against polio, tuberculosis, diphtheria, measles etc. Vaccination against these diseases is given as a routine during infancy and early childhood.

For example:

b. Passive immunization

Passive immunization is useful only when exposure to infection has just occurred. The duration of immunity induced in case of passive immunization is short and variable (1-6 weeks). Undesirable reaction may occur especially if antiserum is of non-human origin.

Passive immunization has a limited value in amass control of diseases. It is recommended for a non-immune person under special circumstances. Three types of preparation are available for passive immunization.

i.Normal human immunoglobulin (Ig)

Normal human immunoglobulin is an antibody-rich fraction obtained from a pool of at least thousand donors. The WHO has laid down definite standards for its preparation. For example, the preparation should contain at least 90% intact IgG, all IgG sub-class should be present, there should be a low IgA concentration etc.

ii. Specific human Ig

The specific human Ig should be maintained at least five times the antibody potential of standard preparation per unit volume. These preparations are made from theplasma of patients who have recently recovered from an infection or are obtained from individuals who have been immunized against a specific infection.

iii. Antisera or anti-toxins

The term antiserum is applied to materials prepared in animals. Since human Ig preparations exist only for a small number of diseases, anti-toxin prepared from non-human sources are still the mainstay of positive immunization.

c. Combined passive and active immunization

In somediseases, for example, tetanus, diphtheria, rabies etc, passive immunization is often undertaken in conjugation with inactivated with vaccine products to provide both immediate passive immunity and slowly developing anactive immunity. But according to therecent recommendation, immunoglobulin (Ig) should not be given within three weeks before or until two weeks after administration of a life attenuated vaccine. However, there are theexception to this rule as for example, the simultaneous administration of Hepatitis B vaccine and Hepatitis B immunoglobulin.

d. Chemoprophylaxis

It refers to the medication for the purpose of preventing diseases or infection, for example, antibiotics may be given to the patients with the disorder of immune system function to prevent the bacterial infection (particularly opportunistic infection). It may be administrated to the individual to limit the spread of an epidemic or to prevent recurrence.

e. Non-specific measures

Non-specific measures to interrupt pathways of disease transmission include improvement in the quality of life. For example, better housing, water supply, sanitation, nutrition, education etc.

References

Gordis, L. Epidemiology. third edition. 2004.

Joshi, Banjara. Fundamentals of Epidemiology. Kathmandu: Quality Printing Press, 2007

Park, K. Park's Text Book of social and prevention Medicine. 18th edition. 2008.