What are Infection and Transmission?

The infections are generated by the pathogenic organisms present in the environment. They maintain the capacity to invade a host body and establish colonies. A disease caused by such infectious agents is called a communicable disease or transmissible disease. These diseases spread through diverse means including blood, food, water, air, or vectors.

Types of Infections

Various microbes and eukaryotic organisms are concerned with causing infections in the body. Infectious diseases are classified according to the causative agents. The classification encompasses bacterial diseases, viral diseases, fungal diseases, helminth infections, and protozoan infections.

The viruses are small, conditional living organisms with the potential to inflict a disease in the eukaryotic host. They can take over the transcription and translation mechanisms that occur within a cell. They transport their genetic material into the host cell to reconcile these processes. Eventually, the host assists the virus to manufacture viral proteins that disrupt the normal operation of the host’s body.

The pathogens are grouped based on their mode of action and they include the primary and opportunistic pathogens. This classification depends on the effect generated by the host immune system. The intrinsic virulence and colonization of the microbes are found to be major factors for causing infections by the primary pathogens. These pathogens are mostly found to be host-specific. Opportunistic pathogens are the pathogens that become functional when the immune system is suppressed. The immune system is compromised during immunodeficiency when the body is more prone to infection by opportunistic microbes.

Modes of Transmission

There are different modes of conveyance of pathogenic microbes. One of the most prominent modes of transmission is through vectors. The vectors are carrier agents, which are concerned with the transfer of infectious microbes between the organisms. The most common vector is the mosquito and it is found to be a cause of a large number of communicable diseases. The infectious agents are also transferred through aerosols, water, and food. The consumption of improperly cooked food can also result in the development of various infections. The consumption of untreated water can also transfer certain infectious agents and can destabilize the normal functioning of the body. The microbes are also transferred through blood transmission, where the blood possesses numerous infectious agents. Patients with certain disease histories are not chosen for donating the blood as it increases the chances of spreading various viral infections between the donor and the acceptor.

Airborne infections are normally spread through the transfer of aerosols from the body. The activities such as coughing and sneezing discharge a large number of aerosols into the environment and these aerosols can harbor a large number of infectious agents. These aerosols are transferred into the respiratory system of other organisms and results in the development of the same infections in the new host. Numerous diseases are transferred through the wastes, which contaminate the water. The sexual transition is also observed to be a major mode of transmission of microbes. The fluids transferred during sexual contact can have a large number of infectious pathogens and can cause severe infections. The infections transferred during transplantation or other medical procedures are referred to as iatrogenic transmission.

Signs of Infections

There are diverse signs and symptoms specific to different infections. Inflammation is found to be a common sign in all types of infections. It is a result of the innate immune response triggered by the immune system. The other symptoms that are concerned with the infections include chills, pains, aches, fevers, weight loss, fatigue, and loss of appetite. The symptoms including runny nose, coughing, and skin rashes are also part of infections. Certain infections are detected to be asymptomatic. This feature is commonly observed in immunosuppressed patients, where their immune system fails to elicit a reaction in the body. The symptoms vary for different types of infections. The important symptoms of bacterial infections include heat, swelling, redness, and pain. The pain is detected in specific regions of the body.

Pathophysiology of Infectious Diseases

The colonization is the primary step employed by the pathogenic microbe mediated after invading a host body. The microbial count is found to be doubled during this process and it will alert the immune system to take defensive measures to restrict the colonization process. Certain toxins are discharged into the circulating blood during this process and disease occurs in the body with the rise of blood toxicity and disruption of the normal working condition of the body. The disease mainly occurs in a compromised host immune system because it favors the microbes to inflict damages on the host tissues and organs and will consequently result in failure of the normal metabolism of the body. Some of the infections are recognized to be tenacious as they are not completely removed from the host body due to the inability of the immune system or the elevated virulence of the pathogens.

Importance of the Immune System

The important disease-causing agents in the environment include bacteria and viruses. These causative agents can invade the host body and disrupt the function of the immune system to cause distinct diseases. The immune system identifies most of the disease-causing microbes and fights against them to suppress their invasive behavior. The mammals resist these infections through rapid innate responses and slower adaptive responses. The rate of transmission is directly proportional to the level of pathogenicity of the microbe. The mammalian responses to these infections include inflammation, which is followed by the secondary response. There are numerous medications to resists the replication of these microbes in the body and these include antifungals, antibiotics, antivirals, and anthelminthic. The antivirals are active against viruses and the antifungals resist the activity of the pathogenic fungi. The antibiotics are most active against bacterial infections.

Context and Applications  

This topic is significant in the professional exams for both undergraduate and graduate courses, especially for

• Bachelors. in Biology
• Bachelors in Microbiology
• Masters. in Microbiology
• Masters in Microbial Biotechnology

Related Concepts

Foodborne illness, Epidemiological transition, Infection control