Direct Contact Disease

The spread of infection requires three elements. The first is; A source of infecting microorganisms: This could be an exogenous infection which arises from microorganisms external to the individual and do not exist as normal flora. They usually have a preferred portal of entry like the gastrointestinal for Salmonella. Another source is endogenous infections which can occur when part of the client’s flora becomes altered and an overgrowth results e.g. Yeasts infection. Second requirement is means of transmission for the microorganism, which also explains the three primary modes of pathogen transmission. For example, vertical transmission is when a pathogen is

Infection is the process where germs enter a susceptible area in the body, where they multiply, resulting in disease.

through a break in otherwise healthy skin – such as a cut, insect bite or other injury – this is known as primary impetigo

This model show the relationship between the causation, host and the environment. In Contagion, the agent is the presence of the MEV-1 virus, which is accompanied by fever, cough, foaming of the mouth and possibly death. The host is the organism affected by the agent, in this case any individual who experienced the disease. Finally, the environment, which takes into account every factor leading up to the spread of the virus. In the case of the film, an environment containing a lack of hygiene, direct transmission and no immediate health care all together led to a rapid spread of the virus.

A communicable disease chain is the mechanism by which an infective agent or pathogen is transmitted. The chain requires an infective agent, a source of infection, a mode of transmission and a host. An example of an infective agent could be bacteria, a virus, fungus, protozoan or helminth. The source of infective agents can be transmission from host to host, an infected human or animal, insects, soil or livestock. The mode of transmission is how the infective agent is carried from host to host. Transmission can be by air, ingestion or physical contact. To complete a life cycle or to replicate, the infective agent requires a host.

Epidemiologists use a tool called, epidemiologic triangle to help understand infectious disease. “The epidemiologic triangle is a traditional model that characterizes infectious disease causation” (Merrill, 2017, p. 178). The triangle consists of an external agent, a susceptible host, and an environment that brings the host and the agent together. The agent, or the “what” of the Triangle, is the cause of the disease. The host or the “who” of the Triangle, can be the organism that gets sick, as well as any animal carrier (including insects and worms) that may or may not get sick. The environment, or the “where” of the Triangle, is the favorable surroundings and conditions external to the host that cause or allow the disease to be transmitted.

Kissing, sneezing, sharing/ touching an object, such as a doorknob, soon after an infected person, you might be exposed to infection. Transmission occurs when you touch your mouth, nose, or eyes before thoroughly washing your hands. Germs can also be spread through contaminated blood products, medical supplies or sexual

The rise of agriculture, dense population, development of world trade route, and dealing society with demotic animals are the common factors that make a situation for microbes to evolve infection diseases. These factors made a large profit for microbes that can make situation in which a large number of people get the same diseases, and each factor has a distinct reason in evolving the epidemic. For example, millions of Roman population died due to smallpox since Rome made contact with European countries for trade purpose. Sometimes arriving an infected person from a local area to another could kill half of million populations through history, major killers include flu, tuberculosis, malaria, smallpox, plague, measles, and cholera. These infection

The Centers for Disease Control and Prevention (CDC) define epidemic as “the occurrence of more cases of disease than expected in a given area or among a specific group of people over a particular period of time.” Epidemic of an infectious disease can be precipitated by a change in the host population, for example, an increase in the density of a vector species or an introduction of a new parasite due to an ecological disaster (flooding, famine, earthquake, etc). Epidemic can also be caused by human behavior (population growth and migration, war, sexual behavior, urban decay, etc), international travel (movement of goods and people), technology and industry (widespread use of antibiotics, organ/tissue transplantation, food processing/packaging, etc), and microbial evolution (adaptation of microbial organism to the environment). In the recent years, delayed or inadequate prevention programs or lack of effective communications between the public health agencies has contributed to the insurgence of epidemics.

The way the body responds when it encounters foreign particles of bacterial pathogens is by it having some cells called phagocytes that will recognize these pathogens, therefore a large number of phagocytes will be sent to the location of where the pathogens were encountered and the defense genes will activate, having proteins go through transcription and translation in order to kill the pathogens in the body.

This results in a massive influx of leukocytes especially neutrophils to the site of infection.

A pro-inflammatory response triggered by infected macrophages causes recruitment of the mononuclear cells at the site of infection. The T-cells interact with the macrophages and activate them by releasing the cytokine, IFN-. Activated macrophages are more efficient at killing Mtb. At this stage of infection, antigen presentation also activates B-cells which produce antibodies against Mtb. A consolidated mass of infected host cells and immune cells forms a granuloma. The granuloma consists of infected macrophages, foamy macrophages that contain stored oil droplets which serve as the bacterial nutrition, T-cells, B-cells in the earlier stages. When the bacillary load becomes static, the infection is said to be “latent”. Early stages of granuloma formation also witnesses vascularisation and supply of blood through newly developed blood capillaries. The granuloma is lined by epithelial cells and fibrous tissue in the later stages. The core of the granuloma is hypoxic (Vandiviere et al., 1956; Via et al., 2008). Granulomas can be resolved due to the action of immune system. With suppression of the immune system due to ageing, HIV infection or malnutrition, the containment of the bacteria

Since the universe evolved, there have been both 'good' bacteria (i.e. aid in digestion) and 'bad' bacteria, often causing infections, disease, and even death in mammals. Therefore, unwanted bacteria being ingested, inhaled, or penetrating a physical barrier can cause multiple issues for that animal. Once the bacteria have penetrated the body's first line of defenses, like entering through a cut for example, there are multiple responses from the body to repel this foreign organism and signal that there is an issue. From this, the rest of the body can work to destroy the bacteria with the innate and adaptive immune response while it also develops memory and defenses against any future invasions of that species.

INFECTION: The penetration and establishment (proliferation) of a pathogen (virus, bacteria, prion) in an organism.

The infectious agent is influenced by the pathogenicity and the virulence. When a disease occurs as a result of how it is measured, for instance if the measure is high this will always cause a clinical disease in a host, whereas if low it rarely causes a disease, even though it frequently colonises humans. Moreover, the measure of the severity of the disease cause is also a factor, as some strains can be more virulent than others. For example, host immunodeficiency is an important factor.