Infectious Diseases and Viruses

question

1- What does the term ‘germs’ usually refer to? 
2- What do all germs have in common? 
3- Define the term ‘modes of transmission’ and give an example. 
4- What is a major disadvantage to a virus, if it replicates too much, too quickly? 
5- If there’s too little of a virus, what is a disadvantage (to the virus) if you don’t experience any symptoms? 
6- List the characteristics of a successful virus. 
7- What does the trade-off hypothesis predict for rhinovirus? 
8- Why does the malaria virus do not require a mobile host? 
9- What can we do to minimize the harmfulness of infectious diseases?
Answer
1. Introduction to Germs
It is highly improbable that a person of adult age could have lived in a household in a semi-sterile environment or worked in an industry which has top-notch cleanliness. Even though people may not be able to visualize germs, mold, and other biohazardous agents, they are always aware of the precautionary methods and practices which aim to bound these unwanted visitors from the realm of clean indoor living or working space. Whether it is teaching children to wash their hands before meals or, in some cases, after, using antibacterial soaps and lotions or spraying down kitchen and bathroom surfaces with chemical disinfectants, people are fighting a seemingly never-ending battle to rid our living spaces of germs. With the recent outbreak of diseases such as SARS, H1N1 virus, and increasingly high numbers of food poisoning cases, it is becoming more important to have a comprehensive understanding of what a germ is and its role as a causative agent of disease. The infamous people of the pre-germ theory era conducted acts such as opening the abdominal cavities of the deceased using bare hands and with no more protection than a blood-stained apron, to cutting the utensils and items used in surgery and not washing them, have an extreme appreciation of what a germ is and the effect of its presence.
1.1. Definition of ‘Germs’
Enough to be seen with the unaided eye. We will call these invisible living beings germs. This definition includes bacteria, fungi, various parasites, and viruses. Germs are limited by being too small to see without a microscope. Bacteria are made up of only one cell, but they are all around us and on us and even in us. Fungi are multi-celled plant-like organisms (such as mushrooms) that also include single-celled species (such as yeasts) and are also found everywhere, often in the form of mold. Many parasites are large enough to be seen. For example, worms are parasites. But this definition includes some parasites that are too small to be seen, such as the ones that cause malaria, which are single-celled organisms called plasmodia. The only exception to this definition is viruses, which are smaller than the smallest cells. While not all viruses are germs in the usual sense, this definition includes them because they are the cause of very many infectious diseases, and they are the only living organisms whose natural state is to exist only inside cells. Viruses are difficult to classify as microorganisms, as they are not truly alive. But they are invariably disease-causing, and this is the key attribute to germs in the context of infectious diseases.
1.2. Common Types of Germs
Viruses are small capsules containing genetic material. They are parasites in other organisms, including people, causing a range of diseases. The common cold, influenza, and warts are all caused by viruses. A virus can only reproduce within the cells of the host it invades, as it reprograms the cell to produce the components necessary for its replication. In most cases, viruses damage or kill the cells, then lie dormant for a period of time before reappearing, causing extensive long-term damage. The cell damage and the immune system’s response to the infection cause the symptoms of viral diseases. The immune system usually eliminates the virus from the body, and the infection is resolved. However, in some cases, such as HIV and Epstein-Barr, the virus evades the immune system, and the infection becomes chronic. Antiviral drugs are selective for viruses in that they can impair virus replication without harming normal host cells. However, due to the difficulty in targeting the viruses and not the host cells, these drugs often have limited effectiveness.
Bacteria are tiny, one-celled creatures that get nutrients from their environments in order to live. In some cases, that environment is a human body. Some bacteria actually cause disease, while others are helpful and even necessary to good health. Lactobacillus bulgaricus, for example, lives in the intestines and helps digest food. The bacteria in yogurt is probably the most known example of Lactobacillus bulgaricus. A few bacteria, such as the mycobacteria, are not harmful in general but can cause disease in a person whose immune system is not working properly. For example, Mycobacterium avium-intracellulare can cause a serious disease. More information is available on this in the Immune System and Disorders Article. Bacteria can cause many types of infections varying in severity. Infections occur as the bacteria try to make the body an environment more suitable for them to live in, reproducing and furthering their harmful effects. In infecting the body, bacteria can damage cells or interfere with cell function. They may release toxins which can damage the whole body. This then becomes a generalized infection. Symptoms of infection can vary but often include inflammation, fever, and fatigue. Bacterial infections are usually treated with antibiotics, which are chemicals designed to destroy or weaken the bacteria. High-level or broad-spectrum antibiotics are effective against a wide range of bacteria, and low-level antibiotics are often used to keep certain bacteria at bay. Amoxicillin use for prevention of Urinary Tract infections is an example of this. Antibiotics seldom have no effect on symptoms since they may cause removal of the bacteria and toxins that have caused damage or particular symptoms. Antibiotics have had a major impact on the length and severity of bacterial infections and on general public health.
Many people are familiar with the term “germs” referring to the tiny, microscopic organisms that cause disease. Until the invention of the microscope, scientists did not realize that germs existed, and people thought that disease was caused by bad air, spirits, a punishment from a god or simply fate. However, we now know that 4 main types of germs cause infectious disease. These are bacteria, viruses, fungi, and protozoa. Each of these types has its own structure, behaviors, and effects on the human body.
1.3. Role of Germs in Infectious Diseases
The organisms explained in the previous sections cause disease because they circle the primary location of the infectious organism that multiplies and causes trouble for the host. Now, disease is essentially a battle between two invasive organisms: the germ and the human. Disease occurs when the germ is successful in the battle with the human. The severity of that battle is what determines the severity of the disease. They are successful at causing disease when there is a portal of entry available to them. They are able to attach to the cells, grow and multiply, remain undetected by the immune system, and then cause damage to the cells and tissues. Germs in general are very adaptable, and that is why they are very successful at causing disease. Unfortunately, not all new strategies for the germ are successful in overcoming the immune system and resulting in disease. An example of this is the common cold, where there are over 200 different viruses that cause cold-like symptoms. Usually, it is insufficient in overcoming the immune system to cause serious illness, and symptoms of disease are only mild. This is known as colonization of the host, and many common diseases are simply a result of the germ trying to colonize and the battle between the germ and human causing only mild disease.
2. Common Characteristics of Germs
2.1. Key Features of Germs
2.2. Similarities Among Different Types of Germs
2.3. Importance of Understanding Germs’ Commonalities
3. Modes of Transmission
3.1. Definition of ‘Modes of Transmission’
3.2. Examples of Different Modes of Transmission
3.3. Significance of Understanding Transmission Methods
4. Viral Replication and Disadvantages
4.1. Consequences of Excessive Virus Replication
4.2. Negative Impact of Rapid Virus Replication
4.3. Effects of Overabundance on Virus Survival
5. Implications of Low Virus Levels
5.1. Disadvantages of Insufficient Virus Presence
5.2. Lack of Symptoms and Virus Survival
5.3. Importance of Detecting Low Virus Levels
6. Characteristics of Successful Viruses
6.1. Traits of Highly Effective Viruses
6.2. Factors Contributing to Virus Success
6.3. Understanding Successful Virus Traits
7. Trade-Off Hypothesis for Rhinovirus
7.1. Predictions Based on the Trade-Off Hypothesis
7.2. Implications for Rhinovirus Survival
7.3. Analyzing the Trade-Off Hypothesis in Rhinovirus
8. Malaria Virus and Host Mobility
8.1. Factors Influencing Malaria Virus Transmission
8.2. Lack of Mobile Host Requirement in Malaria Virus
8.3. Understanding Malaria Virus Transmission Mechanisms
9. Minimizing Harmfulness of Infectious Diseases
9.1. Strategies for Controlling Infectious Diseases
9.2. Importance of Preventive Measures
9.3. Promoting Public Health Initiatives