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Threemethods of disease transmission

Three methods of disease transmission that were identified in theanimation video are contact transmission, vehicle transmission andvector transmission (Cummings, 2007). Vector contact is the spread ofgerms by direct contact, indirect contact or droplets. It includestouching, kissing or sexual intercourse. It may also include motherto child transmission during birth. Droplet transmission occursthrough mucus droplets within a short distance. Indirect contactinvolves spreading of pathogens by inanimate objects known asfomites, which include money, utensils, and medical equipment.

Vehicletransmission’s agents include air, water and food. It may alsoinclude bodily fluids such sweat and saliva. Airborne transmission isby the spread of pathogens by aerosols, which can be either dust ordroplets being transmitted within a meter (Cummings, 2007). Awater-borne transmission is a major mode of transmission for a numberof gastrointestinal diseases such as cholera. On the other hand,food-mode transmission takes place through contaminated or poorlyprepared food.


According to the video, vectors are arthropods that transmit diseasefrom one host to another. This term if often used to describe insectsor arachnids that are part of the pathogen’s life cycle. Twovectors are mentioned in the video, mosquitoes (vector for malaria)and fleas (vector in bubonic plague).












2Pathogens discussed (Streptococcus Pneumonia and Shigella)

Howthey hide from defenses

The pathogens have the ability of detecting foreign cells by lookingout for molecules on the surfaces of the invaders that are not therein the human body. Adaptive defenses such as B cells, antibodies andcytotoxic T cells look for specific antigens on the surface of theinvaders (Cummings, 2007). If it happens that a microbe can hide fromthese surveillance methods, there are high chances that they willreproduces in the body.

When immune surveillance cells such as macro-pathogens are searchingfor the invaders, they reach the surface molecules that are not foundon the host surfaces, such a peptidoglycan. Capsules that surroundthe bacteria are usually composed of polysaccharides that are thesame as molecules, which are found on the host cells. When amacrophage encounters an encapsulated bacterium, it fails torecognize it as a foreign, hence ignores it. This strategy is mainlyused by streptococcus pneumonia, a common case of bacterialpneumonia.

Hidingfrom host

Another tactic for hiding from the host is through survivingphagocytosis. Even if a bacterium may be engulfed by a phagocyte, itnecessarily does not have to be killed (Cummings, 2007). Thetuberculosis bacterium survives within a phagocyte by preventing thefusion of lysosome and phagosome. This prevents the digestive enzymesfrom accessing the bacterium. Bacteria such as Listeria havethe ability of escaping the phagosome and living within thecytoplasm. How they penetrate the host

One way they can attach to the host and cause disease is by havingcertain virulence factors. These factors help them to attach to orpenetrate the host tissues and to escape the host defenses. One groupof virulence factors is enzymes, which are secreted to help thepathogens to penetrate the tissues. This allows them to access thenutrients and reproduce. Some pathogens secrete enzymes that break uphydrochloric acid, which is a polysaccharide responsible for holdingtogether body tissues (Cummings, 2007). By breaking it, the pathogensget an easy way of penetrating the skin. Other pathogens also secretecollagenase, which is an enzyme that helps them to pass through thebarrier. The collagen is digested and creates space for thepenetration of the pathogens deeper into the body.

Otherpathogens secrete an enzyme that digests blood clots by breaking downthe fibrin proteins that provide the structure of the clot.Additionally, their ability to dissolve blood clots allows them topenetrate deeper beneath injured skin and cause more irritations.

Howthey reproduce: ID them using three phenotypic descriptions

Streptococcus Pneumonia reproduces through binary fusion.During this process, it begins with copying its genetic material, andthen polarizing the opposite ends of the bacteria. This is followedby formation of proteins to form a ring in the center (Liu, 2012).This ring creates space for the bacteria to split into two, at thesame time avoiding damage to other copies.

Shigellosis attacks the cells in the large intestines andbegins reproducing by releasing an exotoxin known as shigatoxin (Liu, 2012). This toxin damages the blood vessels. This createsthe condition for it to reproduce in the intestinal cells, laterspilling out into the large intestines.

EmergingInfectious Diseases

Emerging Infectious Diseases have no boundaries, and they there is achallenge to protect workers against them in the workplace. Thepathogens discussed in this paper are not identified in the workplaceas a risk for the Infectious Diseases in the Workplace. This isbecause they are not responsible for diseases, which have increasedin the past 2 decades, nor do they seem to threaten to increase inthe future.

Totalcases and related mortality reported

According to Fratamico, Bhunia &amp Smith (2008), the case mortalityrate for streptococcus pneumonia is 5%-7%, and might be higherin elderly persons. The mortality rate for Shigelloris averages2%-12%.


Cummings, B. (2007). Epidemiology. Retrieved on 18 March 2015from:http://www.pearsoncustom.com/mct-comprehensive/asset.php?isbn=1269879944&ampid=5202

Fratamico, P.M, Bhunia, A.K. &amp Smith, J.L (2008). Food-bornePathogens: and molecular biology. Boca Raton, FL:CRC Press.

Liu, D. (2012). Molecular detection of human parasitic pathogens.New York, NY: Routledge.