In the science of epidemiology, reference is made as regards to population and not individuals. Population and not individuals is usually studied in an epidemiological investigation. This kind of study is usually done in reference to time because time causes or brings about some variations in the affected population. Epidemiology not only incorporate data on the area of infectious diseases in population groups but likewise those resulting from anatomical, deformities, genetic, constitution, metabolic dysfunction, malnutrition, occupational pursuit and the process of aging. These factors are explained briefly in below below delving into the methods of epidemiological studies.
Anatomical deformities refer to physical deformity in a person. Some deformities in people make them more prone to infections than normal people who are without deformities. For example, albinism is an anatomical deformity in people (albinos) and this makes such groups of people to be prone to certain skin cancers because of the absence of the pigment, melanin in their skin. This does not occur in non-albino persons who possess this pigment. Other anatomical deformity can be seen in blind, lame and crippled people.
Because the phenotype of a host is dependent on its genotype, selective pressure on the genetic constitution/genotype of a host can result to changes in their phenotype (i.e. their outward appearance). For example, some individuals have the “AS” genotype (abnormal) while others have “AA” genotype (normal). The “AS” genotype is as a result of selection pressure on the genetic constitution of a host. Individuals with “AS” genotype are resistant to some infections like malaria while those with “AA” genotype are more prone to malaria infection.
Metabolic dysfunction can occur in an individual when there is a deviation from the normal metabolic function of the body to an abnormal metabolic function. The kind of diet an individual eats and exposure to certain substances in the environment can bring about metabolic dysfunction. Certain infectious agents can cause metabolic dysfunction. For example, when people are infected with a particular infection such as infection with the human immunodeficiency virus (HIV), it can lead to metabolic dysfunction of the host immune system – and this predisposes the HIV-infected individual to several microbial infections. Also, most people have non-pathogenic Entamoeba histolytica infection (Amoebiasis) which can be transformed into the pathogenic E. histolytica under certain conditions like:
- Intake of high carbohydrate (CHO) food
- Intake of low protein food
- Intestinal infections
- Schistosoma haematobium infection
- Reduction in the normal bacterial flora of the gastrointestinal tract (GIT) by indiscriminate use of antibiotics.
The presence of these aforementioned factors alters or transforms the non-pathogenic E. histolytica to the pathogenic E. histolytica. When this occurs, they now start to cause an outbreak of amebiasis in that community. The normal bacterial flora in the GIT is meant to check the growth of E. histolytica, but when these conditions/factors mentioned above becomes eminent or prevalent in the individual, the non-pathogenic E. histolytica changes to the pathogenic E. histolytica, and this could result to the outbreak of amoebiasis in the population.
Malnutrition occurs when an individual is under feeding or over-feeding. It can predispose people in a population to several infections. This is because malnutrition has a way of reducing the immune system of a host thereby making them more prone to microbial infection. People should eat well balanced diet in order to counter this effect.
Certain jobs that people do predispose them to infections at a much faster rate than people who are not involved in such jobs/occupations. For example, hospital personnel are more prone to acquiring nosocomial infections than non-hospital personnel’s. Nosocomial infections are infections acquired in the hospital environment. They are hospital-acquired infections. Also, commercial sex workers are more prone to acquiring sexually transmitted disease (STDs) such as syphilis and gonorrhea than individuals who are not commercial sex workers. Farmers, builders and road construction workers are more prone to fungal infections arising from inhalation of fungal spores as a result of their job.
PROCESS OF AGING
Susceptibility of people to infection in a population varies with age. Aging process is not only in the adults but it occurs from childhood to adulthood. Susceptibility to infection in the infants, toddlers, juvenile, young adult, adult, and the elderly varies. For example, some diseases like measles are more prone in children than in adults. Knowing the age category that is more susceptible to the infection/disease in question helps the epidemiologist in directing control measures/strategies towards the susceptible age group that is in dare need of medical intervention.
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