COMMUNICABLE DISEASES, CONTROL and PREVENTION

COMMUNICABLE DISEASES (CONTROL & PREVENTION)

INTRODUCTION TO COMMUNICABLE DISEASES

  The main aim of this post is to discuss communicable disease. Though we may not go into details but we will try as much as possible to cover the most important and key topics in community or public health some of which include but not limited to the following:

Communicable diseases, infectious diseases, agents of diseases, Epidemiology, Hosts, Incubation period,Clinical infection, Sub-clinical infection, transmission route, Transmission cycle, communicable disease prevention, Reservior, levels of prevention, Primordial prevention, Primary prevention, Secondary prevention, disease surveillance, immunity.

Diseases that spread from person to person, or from animals to people are called communicable or infectious diseases. Together with malnutrition, they are today the major cause of illness in Africa. It occurs at all ages but are most serious in childhood due to intensive exposure and poorly developed immunity. Communicable diseases are to a great extent preventable.

“Emerging infectious diseases”- defined as infections that have increased in incidence during the last couple of decades or threaten to increase in the near future. E.g. viral, bacterial etc

Infection- It is the invasion and multiplication of microrganisms in or on body tissues that produce signs and symptoms as well as an immune response. Such reproduction injures the host by causing cellular damage from toxins or intracellular multiplication, or by competing with the host’s metabolism.

Communicable diseases are very important:

• Many of them are very common.

• Some of them are serious and cause death and disability.

• Some of them cause widespread outbreak of disease, that is, epidemics.

• Most of them are preventable by fairly simple means.

• Many are particularly serious and more common in infants and children.

AGENTS OF DISEASES

Living organisms that cause communicable diseases are of different sizes and sorts and they are the agents of diseases.

• Metazoa:- largest and made up of many cells eg. Tapeworm and filaria.

• Protozoa:- smaller single-cell organism and only be seen using a microscope. Eg. Mps, amoebae.

• Bacteria:- smaller simple single cells best seen under a microscope after staining with dyes.

• Rickettsiae and chlamydiae:- smaller and can only multiple within cells.

• Viruses:- smallest, cannot be seen with ordinary microscope.

PATTERN OF COMMUNICABLE DISEASE/ EPIDEMIOLOGICAL APPROACH TO HEALTH AND DISEASE

Epidemiology is the study of the distribution and determinants of health-related states or events and the application of this study to the control of diseases and other health problems

Different diseases are common in different places and at different times.

Agents:- the living organisms that cause the disease.

Hosts:- the people they infect

Environment:- surroundings in which they live.

Relationship Between Agent, Host, and Environment

The agent needs a suitable environment to grow.

The hosts are affected by the environment.

The environment can affect the agent.

A balance between the agent, the host and the environment is very necessary.

The host and infection

• Incubation period:- the time between infection and the appearance of symptoms and signs of illness is the incubation period. The shorter the period, the more rapid the disease can spread or die out in the community.

• Clinical infection:-  Clinical infection are infection with symptoms and signs

• Sub-clinical infection:- Sub-clinical infection are infection without symptoms and signs, but spread may occur by transmission of the organism by the infected person – carriers.

• No infection:- the organism is killed by the person

Transmission route:- transmission route is the way in which an organism leaves the infected host or source and travels to a new susceptible person. The source of an infection can be an infected person, animal or soil.

Transmission cycle:-  Transmission cycle describes how an organism grows, multiples and spread.

Main transmission routes are:

Direct contact (skin, sex etc)

Vectors

Faecal contamination of soil, food and water.

Contact with animals and their products.

Airborne (inhalation)

Transplacental (during pregnancy)

Blood contact (injection, surgery, blood transfusion)

CONTROL/PREVENTION OF COMMUNICABLE DISEASES

In communicable disease prevention, the aim of controlling communicable diseases is to tip the balance against the agent. This can be done by:

1. Attacking the source

1. Treatment:- use of drugs to destroy the organism. Effectiveness of treatment depends on how many of the cases can be reached & whether the treatment affects the agent’s capacity to reproduce. Sub-clinical cases must also be treated (Mass treatment – treating everybody, without checking whether individuals have the disease or not).

2. Isolation:- preventing infected person from getting close contact with other people except those who are providing care. (Used to control highly infectious and serious conditions).

3. Reservior control:- used in those diseases that have their main reservior in animals. (Mass treatment, chemoprophylaxis or immunisation of the animals can be carried out as well as Separating humans from animals or killing the animals also destroys the reservoir).

4. Notification:- prompt information is given to local health authority about any suspicion of a person suffering from an infectious disease.

2. Interrupting transmission

(a) Environmental sanitation:- faeco-oral route, refuse and dirty living conditions and people living in crowded rooms

(b) Personal hygiene & behaviour change:-Improve personal hygiene and Changes in personal behaviour

(c) Vector control:-transmission cycle may be affected if vectors are killed off or reduced. (Alter the environment, using toxic substances and using other living organisms that attack the vector).

(d) Disinfection and sterilisation:- aimed at destroying the organism when it is in the environment. (Use of chlorine in wells, Boiling potentially contaminated water/food and Sterilising surgical instruments)

3. Protecting the host

(a) Immunisation:- increases host resistance by strengthening the internal defence system.

(b) Chemoprophylaxis:- use of drugs that protect the host by Suppressing the disease (use of SP in malaria) and preventing infection (meningitis, TB).

(c) Personal protection:- the spread of some disease can be limited by the use of barriers against infection. Eg shoes, bednets, insect repellents.

(d) Better nutrition

Levels of Prevention

The levels of prevention are:
Primordial prevention:-  Primordial prevention seeks to prevent, at the earliest possible stage, the activities, which encourage the emergence of lifestyles, behaviours and exposure patterns that contribute to increased risk of disease. This level of prevention is targeted at the total population and selected groups.

The aim of primordial prevention is to avoid the emergence and establishment of social, economic and cultural pattern of living that are known to contribute to an elevated risk of disease.

Eg: heavily regulating and controlling the tobacco industry before it was established.

Primary prevention:- Primary prevention may be defined as the prevention of disease through the control of exposure to risk factors. Primary prevention of disease is preventing healthy people from becoming sick. Example: Use of condoms in the prevention of HIV infection.

This level is targeted at the whole population with the aim of reducing average risk, or specific people at high risk as a result of particular exposure.

Methods of primary prevention are;

• Immunisation.

• Provision of safe water supply.

• Health education

• Provision of adequate housing.

• Safe disposal of human excreta.

• Control of vectors of disease.

• Preventing exposure to lead in the environment.

• promoting non-smoking.

Secondary prevention:-  Secondary prevention is the application of available measures to detect early departures from health and to introduce appropriate treatment to cure the patients and prevent chronic disease or disability. Secondary prevention is directed towards those people who are in the subclinical or the early clinical stages of disease.

For effective secondary prevention, you will have to actively seek out early cases of the disease in the community by carrying out a household survey or telling people to come to the clinic for examination.

Eg; malnutrition in children, anaemia.

NB: Secondary prevention can be applied only to diseases in which the natural history includes an early period when it is easily identified and treated.

Tertiary prevention:- Tertiary prevention is the prevention of more disability and death in a patient who cannot be cured. Tertiary prevention is an important aspect of therapeutic and rehabilitation medicine. It consist of the measures intended to reduce impairments and disabilities, minimise suffering caused by departures from good health and promote patients’ adjustment to incurable conditions.

Tertiary prevention has two aims:

1. Treatment to prevent more disability and death.

2. New training and special education to help the patient to return to some useful work and life in the community.

Eg: blindness due to vitamin A deficiency, Diabetes and Stroke.

Disease Surveillance

Various methods can be used to carry out epidemiological investigations: Disease surveillance and descriptive studies can be used to study distribution; analytical studies are used to study determinants.

Public health surveillance is the continuous, systematic collection, analysis and interpretation of health-related data needed for the planning, implementation, and evaluation of public health practice.

Importance of Disease Surveillance

• Serve as an early warning system for impending public health emergencies;

• Document the impact of an intervention, or track progress towards specified goals; and

• Monitor and clarify the epidemiology of health problems, to allow priorities to be set and to inform public health policy and strategies.

Types of Disease Surveillance

1. Sentinel surveillance systems consist of a sample of health facilities or laboratories in selected locations that report all cases of a certain condition to indicate trends in the entire population.

2. Household surveys can be used to monitor diseases if the surveys are consistent and repeated periodically, say every three to five years.

3. Laboratory-based surveillance is used to detect and monitor infectious diseases. For example, for food-borne diseases such as salmonella, the use of a central laboratory to identify specific strains of bacteria allows more rapid and complete identification of disease outbreaks than a system that relies on reporting of syndromes from clinics

4. Integrated disease surveillance and response (IDSR) strategies bring together data from health facilities and laboratories in systems designed to monitor communicable diseases.

Immunity

Immunity is your body's defense system against infectious diseases. In your immune system, there is a complex of network of cells, tissues and chemicals that fight infection and kill infectious organisms when they invade the body.

Categories

There are three categories of immune protection, all of which help protect the body from infectious diseases. Immunity can be active or passive and natural or artificial. That means you immune system still defends a vaccination, a vaccination places an active or inactive disease in your body only a small amount so your immune system can make the right antibodies for that disease.

When attacked an organism has several means in which it can prepare to defend itself in event of attack.

• Active Immunity - Vaccines are used for health purposes to expose our bodies to a particular antigen. These antigens are usually killed or severely weakened to decrease their potency. After destroying these pathogens, the body stores some T cells as memory cells, due to the fact they code for a particular antigen and can be when needed. This memory in T cells can be a means of artificially acquiring immunity while a genuine attack by a pathogen is a naturally acquired type of immunity.
• Passive Immunity - This is where immunity to particular antigens as a result of genetic traits passed on from parents rendering the offspring immune to a particular pathogenic threat.

I believe we have covered the target topics we set for ourselves which are Communicable diseases, infectious diseases, agents of diseases, Epidemiology, Hosts, Incubation period,Clinical infection, Sub-clinical infection, transmission route, Transmission cycle, communicable disease prevention, Reservior, levels of prevention, Primordial prevention, Primary prevention, Secondary prevention, disease surveillance, immunity.