Pathogens and Diseases: Pathogens are common characteristics of everyday environment as soil contains huge number of bacteria per cubic centimeter while air contains fungal spores. The existence of pathogens in everyday environment emanates from the fact that microorganisms are deposited through touching of various surfaces like tables. Pathogens can be described as disease-causing agents such as infectious microbes, and parasites. While the infectious microbes include viruses and bacteria, parasites include protozoa and fungi. Notably, microbes are only considered as pathogens if they cause harm or diseases since not all microbes are harmful (Koo, 2009). There are opportunistic pathogens, which are organisms that are normally part of the natural flora of the body. These organisms become harmful or pathogens after an invasion like the occurrence of an accidental injury or surgery.

Spread of Pathogens:

Since pathogens are common disease-causing agents, they spread in various ways to cause harm or illnesses. Some of the major ways with which these organisms spread include droplet infection, direct contact, contaminated food and water, vectors, and bodily fluids. Droplet infection occurs when people cough, talk, sneeze, and even breathe while the direct contact takes place through touch or sexual intercourse. Drinking contaminated water and eating raw or uncooked food results in the consumption of large numbers of microorganisms that cause diseases. In contrast, vectors are animals spreading the disease-causing agents like mosquitoes whereas pathogens can spread through bodily fluids ("Pathogens Cause Disease," n.d.).

How Pathogens Cause Disease:

Pathogens cause diseases through various ways that are linked to the different disease-causing organisms like bacteria and viruses ("How Pathogens Cause Disease," n.d.). After an infection, the bacteria grow and reproduce within the cells in the body. The growth and division of bacteria leads to the production of toxins that can damage the cells. Toxins can cause damages because they are poisonous and sometimes damage cells directly as they grow. On the other hand, viruses take over a person's genetic material of the cells after an infection because they can't reproduce outside of the cells of their host. After making copies of the virus, they kill infected cells, spread, and damage body tissues.

The possibility of an infection is normally dependent on the ability of the pathogen to adhere to the cells in specific tissues. Moreover, many pathogens cause damage and penetrate tissues based on their release of toxins or enzymes (Chiras, 2011). Some enzymes assist the pathogens to resist body defenses and enhance the virulence of an infectious microbe. In order to help the pathogens in fighting body defenses, the enzymes interfere with some cellular functions or barriers that prevent invasion.

The Immune System and Infectious Diseases:

As previously mentioned, infectious diseases are transmitted through various ways like droplet infection and direct contact. The immune system is the most important part of the body in relation to the occurrence and spread of diseases. The basic role of the immune system is to protect the body against the infectious microbes like fungi, protozoa, viruses, bacteria, and multi-cellular parasites (Malone & Lindsay, 2006). In normal individuals, the immune system is usually efficient in restraining most infections to ensure that the infectious diseases are short lived and leave without permanent damage.

There is a great need for the immune system to be effective in combating all type of diseases, particularly the infectious ones because the disease-causing modus operandi of pathogens tends to be complex (Elgert, 2009). The immune system can help in combating infections through immune responses that are elicited by foreign substances and reactions against many tumors. Every type of infection requires a wide range of immune responses since the infectious microbes come in several different forms.

Immune responses are classified into two major categories i.e. non-adaptive or innate and adaptive immune responses. Innate immunity, which is also known as the native, non-adaptive or natural immunity, is constitutional and acts as the first line of defense against disease-causing organisms (Mayer, 2011). This immunity does not improve upon recurring contact with similar infectious agents. The adaptive immune system is considered as the second line of defense which is also known as the acquired or specific immunity. This type of immunity is usually very specific for a particular pathogen while improving with every successive contact with similar pathogen.

The main similarity between the innate and adaptive immune system is that they both function towards the protection of the body against potentially harmful and disease-causing organisms. However, there are various differences between these two categories of immunity including response to successive contact with the same pathogen as previously mentioned. The other differences...

While the native immune system is created by the natural barriers of the body, the adaptive immune system develops when the body is exposed to particular foreign microorganisms ("The Immune System," n.d.).
The other type of immunity is known as passive immunity that lasts for a short time and is borrowed from another source (Dowshen, 2009). An example of passive immunity is the antibodies in the mother's breast milk that offer the baby temporary immunity to the disorders that the mother has been exposed to.

In its role of combating infectious diseases, the immune system extremely complex and consists of many processes that are not understood ("How the Immune System Fights Disease," 2008). Generally, the cells in the immune system are capable of identifying a disease-causing organism or infectious microbe and try to eliminate the invader. However, the immune system needs the effective coordination of the numerous kinds of cells and chemical in order to function smoothly. The major cells involved in combating diseases by the immune system are white blood cells or leukocytes that come in two main kinds that combine to identify and destroy the pathogens. As the leukocytes circulate in the entire body between organs and nodes through blood and lymphatic vessels, the immune system is effectively coordinated to supervise the body against disease-causing agents.

Specific and Non-specific Defenses of the Body:

The smooth functioning of the immune system involves the use of both the specific and non-specific defenses of the body. The specific defenses are activated when non-specific defenses are ineffective in destroying microorganisms and are designed to match the specific antigen invading the body. These defenses work through identifying particular antigens of a microorganism and destroying it through the components of non-specific system. On the contrary, non-specific defenses simply respond to the presence of non-self cell since they don't identify a microorganism's antigen ("Immune System -- Organs," n.d.). In addition to consisting of external barriers, the lymphocytes, and other reactions, the non-specific defenses tend to be effective in destroying microorganisms. The main difference between these defenses is that non-specific defenses entail the general ways that prevent foreign substances from causing harm to the body while specific defenses target particular bacteria in the body (Tamarkin, 2011).

Cross Infection and Infection Control:

The prevention of cross-infection is usually a fundamental activity for all nurses in the day-to-day practice (Folan & Baillie, n.d.). While the prevention of cross infection is an ethical and legal duty for protecting patients, the risk of cross-infection is high in hospitals as evident in the case study. The main feature in the control of cross infection is the maintenance of hospital environmental hygiene and multi-use equipment. Based on the case study, the cross infection that contributed to the death of 7 patients was the collection procedures for sputum sample from one patient. Therefore, the control of cross infection involves features like use of protective equipment, effective specimen collection and isolation procedures, and use of aseptic methods.

Infection control is based on three major principles i.e. cleanliness, hygiene like hand washing and care, and sterility. The best practices in infection control that have evolved over the years to an extent that they are widely accepted by occupational health and safety groups are rooted in a framework with three control levels. These practices include engineering controls, personal protective measures, and administrative controls ("Infection Prevention," 2007). While engineering controls entails the design of the facility, the administrative controls are protocols for hygiene. The personal protective measures involve the use of equipments in the appropriate manner to control hazards.

The treatment of bacteria and other infectious microbes has involved the use of antibiotics for over half a century. Antibiotics have been used for treatment of these infections because the interrupt the chemical processes that the bacteria use to create their cell walls and prevent them from growing and multiplying. In the past few years, there has been an ongoing health problem caused by the resistance of disease-causing microbes to antibiotic drugs ("Antibiotics," 2012). The resistance usually occurs when the antibiotic drugs can no longer work against the bacteria that causes infectious diseases. Some of the major problems that occur due to the resistance include difficulties in treatment, long-lasting illnesses, extended hospital stays, increased number of doctor visits, and need for expensive medications.

Conclusion:

Pathogens are the leading causes of many infectious diseases in the human body while the immune system…