Everyone experiences illness now and then, in fact part of what makes us human is that we are susceptible to disease. If you’ve ever been sick and most likely you have, you’ve probably found yourself wondering how you got sick in the first place. There are many causes of disease from, germs, to genetics but, all diseases can be placed into one of two categories; communicable, or non-communicable. The word communicable basically means contagious so, a communicable disease is one that can be spread to another person through infection. Non-communicable diseases on the other hand, cannot be spread from person to person because, they are not contagious. Each category has its own causes that will be discussed throughout this lesson Communicable or contagious diseases are caused by pathogens and parasites. Pathogens are germs, while parasites are organisms that obtained nutrition at another organisms expense. Pathogens and parasites can be spread from one person to another through physical contact, contaminated food, or water, coughing, or sneezing, or even through insect vectors. There are a number of different kinds of pathogens and parasites, some of which may be familiar to you while others may be new. One type of pathogen that you’ve probably heard a lot about these viruses. Viruses are not considered living things but, they do need living cells to reproduce, these living cells are called host cells. A viral infection begins when a virus particle invades a cell, the virus then, hijacks the hosts cellular machinery to produce new virus particles. The host cell essentially becomes a virus factory, that is ultimately destroyed by the virus as it multiplies. New virus particles can be spread through the air when the infected person coughs or sneezes, through contaminated food, bodily fluids, or by insect and animal bites. Once spread the new virus particles can infect more cells and multiply even further. Examples of illnesses caused by viruses include the common cold, measles, chickenpox, Aids, and many more unfortunately, there is no cure for viral infections, while medicines may treat the symptoms, and ease the discomfort of the patient. The virus must run its course in your body, and only the immune system can ward off the attack. Antibiotics are not effective against viral infections and can even be harmful to have taken unnecessarily because, they can upset the balance of good bacteria in your body. Taking antibiotics can also increase the chances that the bad bacteria will evolve to resist the antibiotics, a phenomenon known as antibiotic resistance; therefore it is useless to take antibiotics if you have a viral infection. Another type of pathogen that you are probably familiar with is bacteria. Unlike viruses bacteria are alive, they are single-celled organisms that are found everywhere on Earth, from soil, air, and water, to the surface of your skin and even inside your body. Most bacteria are beneficial in some way and do not cause disease. In fact, less than 1% of known bacterial species cause illness in humans. Those that are pathogenic, however can cause some pretty serious diseases. Some examples of diseases that are caused by pathogenic bacteria include; strep throat, whooping cough, pneumonia, scarlet fever, and Lyme disease. Pathogenic bacteria cause infections when they enter your body either through a cut, insect bite, or through mucous membranes, such as your mouth, nose, or eyes. The bacteria reproduce inside your body and many give up toxins that damaged cells and make you sick. Diseases caused by bacteria are treated with antibiotics. Antibiotics kill bacteria by attacking their cell wall or other cellular structures. Viruses do not possess these cellular structures, which is why antibiotics do not work to cure viral infections. Protozoans are another group of single-celled organisms that cause disease. You may not have heard of protozoans before but, you might be familiar with some of the illnesses they caused. Some protozoan infections like Amoebic dysentery, Giardiasis, and Toxoplasmosis, are spread through contaminated food, water, or from person-to-person contact. Others, like Malaria and African sleeping sickness are transmitted by insect bites. Trichomoniasis is sexually transmitted. These illnesses can be treated with anti-parasite medications. Fungi may also act as pathogens, although most fungi do not cause disease. Fungi you most commonly see are mushrooms, and molds; however, most Fungi are microscopic. Parasitic Fungi cause diseases such as athletes foot, Ringworm, Jock itch, and Thrush. Fungal infections usually occur after contact with a contaminated surface, these conditions can generally be treated with topical anti-fungal ointments or creams. The last group of pathogens that cause communicable diseases are parasitic worms, we’re not talking everyday earthworms here. Earthworms are not parasites, nor do they cause disease. Worms that can be pathogenic include a number of different species. Trichinella worms which caused trichinosis, and tapeworms for example, are usually contracted by eating the under cooked meat of an infected animal. In both cases you may experience nausea, diarrhea, and weight loss. Treatment involves oral medications. Hookworms and Schistosome worms which caused schistosomiasis, are contracted through contaminated soil or water. Both cause a rash and possible diarrhea and can be treated with oral medications. Guinea worms are also contracted by drinking contaminated water. In this case the worm burrows through flesh causing pain and burning. There is no treatment except to wait for the warm to emerge from a blister in the skin and slowly extracted by winding the worm around a matchstick. In most cases worm parasites like those just mentioned, are spread when the feces of an infected person contaminate soil or water in areas of poor sanitation. The feces contain worm eggs so, if another person happens to drink the contaminated water or walk in contaminated soil the worms may invade their bodies. As you can see there are quite a few pathogens and parasites that cause disease in humans. Since communicable diseases are contagious, it is important to try to prevent their spread through a population. Strategies for prevention will be covered in a later lesson. While communicable diseases are contagious, and can spread through a community, non-communicable diseases are not contagious so, they cannot be spread from one person to another. Communicable diseases are caused by pathogens and parasites, while non-communicable diseases have their own list of causes. Some non-communicable diseases are genetic. Genetic diseases are coded for in DNA so, a person with this kind of illness is born with it, although they may not show symptoms of the disease until later in life. Some examples of genetic diseases includes, Psoriasis a skin condition, and Cystic Fibrosis which mostly affects the lungs, and is lethal without proper management. Huntington’s disease is another genetic disorder, in which nerve cells in the brain break down, causing loss of coordinated movement and mental decline: usually starting around age 35. Since genetic diseases are the result of non functional or malfunctioning genes. They are not contagious they are hereditary; however, so they may be passed on from one generation to the next. Many non-communicable diseases are the result of lifestyle choices and behavior. A poor diet, and physical inactivity for example; can lead to obesity, diabetes, cardiovascular disease, high blood pressure, and many other conditions. The decision to use tobacco products could lead to asthma or a number of different cancers. While alcohol abuse could lead to cirrhosis or hardening of the liver. These conditions are the result of personal choices, and individual, makes for their life and obviously are not contagious. Illnesses associated with behavior are chronic however, so they often have no cure but, instead require daily medications and behavior management plans. Another cause of non-communicable diseases involves environmental factors like pollution. Chemical contaminants in air, soil, or water, can find their way into our bodies through inhalation, absorption through the skin, or consumption of contaminated food or water. Repeated exposure to chemical contaminants can cause illnesses; like chronic obstructive pulmonary disease or COPD, lower respiratory infections, gastric issues like diarrhea, disruption of the endocrine system: which controls hormones, skin rashes, birth defects, and a host of different cancers. Environmental factors can also serve as triggers for other diseases like asthma, psoriasis or herpes. Environmentally induced illnesses may be experienced by many people in a community, not because they are contagious but, rather because the people of the community share the same environment. Diseases caused by environmental factors often become chronic conditions, that an individual have to manage for extended periods of time with medications or other treatments. The last cause of non-communicable diseases that we will just us in this lesson is age. As a person ages, body systems, and organs can wear out over time and begin to fail. Non-communicable diseases related to age are called degenerative diseases and include arthritis, osteoporosis, and glaucoma among others. Some of these diseases have environmental, genetic and behavioral factors that can contribute to their development as well. Treatment of the degenerative diseases may involve daily medication regimens, pain management, or physical therapy. At this point, you should have a good understanding of the difference between communicable diseases, those that are contagious, and non-communicable diseases which are not contagious. Studying the incidents or frequency of both communicable and non-communicable diseases, is important to improving community health. Figuring out, how diseases appear in a population, which environmental factors might trigger them, how they might be spread?, and the best methods for prevention and treatment, are all important pieces of information when studying disease. People who study the patterns, causes, and effects of diseases are called epidemiologists. Epidemiologist always have plenty of work to do but, work becomes especially busy if there happens to be a serious disease outbreak called an epidemic. Epidemics may occur as a result of the spread of a communicable disease, for example whooping cough. Or an epidemic may refer to a non communicable disease like diabetes. In both instances the number of disease cases during an epidemic is higher than would normally be expected. When an epidemic occurs, Epidemiologists work to contain the outbreak, that may involve quarantine infected individuals, if the disease is contagious. During a quarantine, all the infected individuals are held in isolation to prevent the spread of the disease. Epidemics of non-communicable diseases, do not require quarantines because, they do not spread from person to person. In addition to preventing the spread of communicable diseases, epidemiologists also study the causes of disease and the patterns those diseases exhibit. For example, an Epidemiologist might document the symptoms of an illness, how long it takes for a patient to start showing symptoms, and whether the disease is contagious. Epidemiologists may also studied treatments, or research cures for disease. If an epidemic spreads over a wide geographic range, it is called a Pandemic. AIDS is an example of a Pandemic because, it affects people all over the world. During a Pandemic, Epidemiologist from around the globe work together to stop the disease. While some Epidemiologists work on Pandemics on a global scale, other Epidemiologists work in smaller communities, on what are referred to as endemic diseases. Endemic diseases are common to a specific area or population and generally present a fairly constant number of cases overtime. Malaria for example is a communicable disease, that is endemic to the tropics, certain places in Africa, Asia, and Central, and South America, have ongoing problems with this disease, Other areas, that are cooler and drier do not experience many cases of Malaria because, the environment is not ideal for the mosquitoes that spread it. Tay-sachs is a genetic disease, that causes deterioration of nerve cells and usually results in death by age 4. It is endemic to Ashkenazi Jews and French Canadians, these groups of people therefor experience a higher prevalence of Tay-sachs disease, than other populations. Epidemiologists have a lot of freedom in their career path, they could choose to work with communicable. or non-communicable diseases. With in their own small community, or on a global scale. Perhaps, it is a career that you find interesting or might consider pursuing.
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