new research on the treatment of communicable diseases is important because bacteria and viruses can become resistant to treatments.
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Understanding Emerging and Re
The term "disease" refers to conditions that impair normal tissue function. For example, cystic fibrosis, atherosclerosis, and measles are all considered diseases. However, there are fundamentally different causes for each of these diseases. Cystic fibrosis (CF) is due to a specific genotype that results in impaired transport of chloride ions across cell membranes, leading to the production of abnormally thick mucus. Thus, CF is most accurately called a genetic or metabolic disease. Atherosclerosis, which can lead to heart attacks and strokes, may be considered a disease of aging, because it typically becomes a problem later in life after plaques of cholesterol have built up and partially blocked arteries. In contrast, measles is an infectious disease because it occurs when an individual contracts an outside agent, the measles virus. An infectious disease is a disease that is caused by the invasion of a host by agents whose activities harm the host's tissues (that is, they cause disease) and can be transmitted to other individuals (that is, they are infectious).
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Understanding Emerging and Re-emerging Infectious Diseases
The term "disease" refers to conditions that impair normal tissue function. For example, cystic fibrosis, atherosclerosis, and measles are all considered diseases. However, there are fundamentally different causes for each of these diseases. Cystic fibrosis (CF) is due to a specific genotype that results in impaired transport of chloride ions across cell membranes, leading to the production of abnormally thick mucus. Thus, CF is most accurately called a or disease. Atherosclerosis, which can lead to heart attacks and strokes, may be considered a disease of , because it typically becomes a problem later in life after plaques of cholesterol have built up and partially blocked arteries. In contrast, measles is an disease because it occurs when an individual contracts an outside agent, the measles virus. An infectious disease is a disease that is caused by the invasion of a host by agents whose activities harm the host's tissues (that is, they cause ) and can be transmitted to other individuals (that is, they are ).
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Nature of Infectious Diseases
Microorganisms that are capable of causing disease are called pathogens. Although microorganisms that cause disease often receive the most attention, it is important to note that most microorganisms do cause disease. In fact, many probably provide some protection against harmful microorganisms because they effectively compete with the harmful organisms for resources, preventing them from growing.
A true pathogen is an infectious agent that causes disease in virtually any susceptible host. Opportunistic pathogens are potentially infectious agents that rarely cause disease in individuals with healthy immune systems. Diseases caused by opportunistic pathogens typically are found among groups such as the elderly (whose immune systems are failing), cancer patients receiving chemotherapy (which adversely affects the immune system), or people who have AIDS or are HIV-positive. An important clue to understanding the effect of HIV on the immune system was the observation of a rare type of pneumonia among young men caused by , an organism that causes disease only among the immunosuppressed.
The terms "infection" and "disease" are not synonymous. An infection results when a pathogen invades and begins growing within a host. Disease results only if and when, as a consequence of the invasion and growth of a pathogen, tissue function is impaired. Our bodies have defense mechanisms to prevent infection and, should those mechanisms fail, to prevent disease after infection occurs. Some infectious agents are easily transmitted (that is, they are very contagious), but they are not very likely to cause disease (that is, they are not very virulent). The polio virus is an example: It probably infects most people who contact it, but only about 5 to 10 percent of those infected actually develop clinical disease. Other infectious agents are very virulent, but not terribly contagious. The terror surrounding Ebola hemorrhagic fever is based on the virulence of the virus (50 to 90 percent fatality rate among those infected); however, the virus itself is not transmitted easily by casual contact. The most worrisome infectious agents are those that are both very contagious and very virulent.
In order to cause disease, pathogens must be able to enter the host body, adhere to specific host cells, invade and colonize host tissues, and inflict damage on those tissues. Entrance to the host typically occurs through natural orifices such as the mouth, eyes, or genital openings, or through wounds that breach the skin barrier to pathogens. Although some pathogens can grow at the initial entry site, most must invade areas of the body where they are not typically found. They do this by attaching to specific host cells. Some pathogens then multiply between host cells or within body fluids, while others such as viruses and some bacterial species enter the host cells and grow there. Although the growth of pathogens may be enough to cause tissue damage in some cases, damage is usually due to the production of toxins or destructive enzymes by the pathogen. For example, , the bacteria that causes diphtheria, grows only on nasal and throat surfaces. However, the toxin it produces is distributed to other tissues by the circulatory system, damaging heart, liver, and nerve tissues. , the infectious agent associated with several diseases including strepthroat and "flesh-eating disease," produces several enzymes that break down barriers between epithelial cells and remove fibrin clots, helping the bacteria invade tissues.
Figure 3
Emerging and re-emerging infectious diseases threaten all countries. Ebola hemorrhagic fever emerged in African villages; schistosomiasis is re-emerging in Egypt, largely as a consequence of building the Aswan Dam; and legionellosis was identified after (more...)
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Microbes That Cause Infectious Diseases
There are five major types of infectious agents: bacteria, viruses, fungi, protozoa, and helminths. In addition, a new class of infectious agents, the prions, has recently been recognized. A brief review of the general characteristics of each of these agents and examples of some diseases they cause follows.
Topic Test #12 (pass with 100%) Flashcards
Study with Quizlet and memorize flashcards terms like New research on the treatment of communicable diseases is important because bacteria and viruses can become resistant to treatments., If you contract a contagious illness from being bitten by a mosquito, this would be considered contraction through __________. A. airborne contact B. surface contact C. direct contact D. vector contact, Select the description that would represent a pathogen that would be considered a virus. A. genetic material that is surrounded by a protein coat and uses a host cell to reproduce B. a single-celled organism that infects animals and plants C. an organism that feeds off others in order to gain its nutrients D. a single-celled organism that can be a parasite and more.
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New research on the treatment of communicable diseases is important because bacteria and viruses can become resistant to treatments.
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If you contract a contagious illness from being bitten by a mosquito, this would be considered contraction through __________.
A. airborne contact B. surface contact C. direct contact D. vector contact
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New research on the treatment of communicable diseases is important because bacteria and viruses can become resistant to treatments.
T
If you contract a contagious illness from being bitten by a mosquito, this would be considered contraction through __________.
A. airborne contact B. surface contact C. direct contact D. vector contact D
Select the description that would represent a pathogen that would be considered a virus.
A.
genetic material that is surrounded by a protein coat and uses a host cell to reproduce
B.
a single-celled organism that infects animals and plants
C.
an organism that feeds off others in order to gain its nutrients
D.
a single-celled organism that can be a parasite
A
If you wanted to reduce your risk of contracting a communicable disease you could __________.
A.
take steps to reduce your immune health
B.
avoid touching your shoes or clothing
C.
wash your hands often
D. start smoking C
Advances in technology have helped prevent some illnesses and diseases.
T
In order to maintain optimal community health, the BEST plan for communities would be to __________.
A.
decrease vaccinations and research new treatments and cures
B.
create laws that control public behavior, like hand washing and blowing your nose
C.
provide community support to elders who are sick and need healthcare treatment
D.
provide health services and regulate food and water supplies
D
White blood cells use __________ to help identify foreign substances in the body.
A.
platelets and white blood cells
B.
antibodies and antigens
C.
enzymes and red blood cells
D.
white blood cells and red blood cells
B
The goal of the flu vaccine is to prevent you from becoming infected with influenza.
T
This single-celled organism may cause disease, but it is also essential to important life processes like decomposition.
A. bacteria B. fungi C. protozoa D. viruses A
Why are regular visits to the doctor important for maintaining your optimal immune health?
A.
to be sure that your overall health is good and to receive the necessary vaccinations
B.
to identify any problems with your immune system early and to increase the stress you are under
C.
to help avoid making contact with sick people and evaluate your weight
D.
to check on the status of your growth and maintain your weight
A
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Infections – bacterial and viral
betterhealth.vic.gov.au
Infections
Infections – bacterial and viral
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Infections – bacterial and viral Actions for this page Summary
Many human illnesses are caused by infection with either bacteria or viruses.
Most bacterial diseases can be treated with antibiotics, although antibiotic-resistant strains are starting to emerge.
Viruses pose a challenge to the body’s immune system because they hide inside cells.
It is possible to be vaccinated against some of the major disease-causing viruses (such as measles and polio), as well as bacterial diseases such as Hemophilus influenza Type b (Hib), tetanus and whooping cough.
On this page
How bacteria and viruses enter the body
Viruses are spread from one person to another by:
Bacteria types
Characteristics of the bacterium
Curing a bacterial infection
Virus types
The body’s response to viral infection
Curing a viral infection
Immunisation against viral infection is not always possible
Where to get help Things to remember
Many human infections are caused by either bacteria or viruses. Bacteria are tiny single-celled organisms, thought by some researchers to be related to plants. They are among the most successful life forms on the planet, and range in habitat from ice slopes to deserts.
Bacteria can be beneficial – for instance, gut bacteria help us to digest food – but some are responsible for a range of infections. These disease-causing varieties are called pathogenic bacteria. Many bacterial infections can be treated successfully with appropriate antibiotics, although antibiotic-resistant strains are beginning to emerge. Immunisation is available to prevent many important bacterial diseases.
A virus is an even smaller micro-organism that can only reproduce inside a host’s living cell. It is very difficult to kill a virus. That’s why some of the most serious communicable diseases known to medical science are viral in origin.
How bacteria and viruses enter the body
To cause disease, pathogenic bacteria must gain access into the body. The range of access routes for bacteria includes:
Cuts
Contaminated food or water
Close contact with an infected person
Contact with the faeces of an infected person
Breathing in the exhaled droplets when an infected person coughs or sneezes
Indirectly, by touching contaminated surfaces – such as taps, toilet handles, toys and nappies.
Viruses are spread from one person to another by:
Coughs Sneezes Vomits
Bites from infected animals or insects
Exposure to infected bodily fluids through activities such as sexual intercourse or sharing hypodermic needles.
Forgetting to wash your hands after handling pets and animals is another way for germs to be taken in by mouth.
Bacteria types
Bacteria that cause disease are broadly classified according to their shape. The four main groups include:
Bacilli – shaped like a rod with a length of around 0.03mm. Illnesses such as typhoid and cystitis are caused by bacilli strains.
Cocci – shaped like a sphere with a diameter of around 0.001mm. Depending on the sort, cocci bacteria group themselves in a range of ways, such as in pairs, long lines or tight clusters. Examples include Staphylococci (which cause a host of infections including boils) and Gonococci (which cause the sexually transmissible infection gonorrhoea).
Spirochaetes – as the name suggests, these bacteria are shaped like tiny spirals. Spirochaetes bacteria are responsible for a range of diseases, including the sexually transmissible infection syphilis.
Vibrio – shaped like a comma. The tropical disease cholera, characterised by severe diarrhoea and dehydration, is caused by the vibrio bacteria.
Characteristics of the bacterium
Most bacteria, apart from the cocci variety, move around with the aid of small lashing tails (flagella) or by whipping their bodies from side to side. Under the right conditions, a bacterium reproduces by dividing in two. Each ‘daughter’ cell then divides in two and so on, so that a single bacterium can bloom into a population of some 500,000 or more within just eight hours.
If the environmental conditions don’t suit the bacteria, some varieties morph into a dormant state. They develop a tough outer coating and await the appropriate change of conditions. These hibernating bacteria are called spores. Spores are harder to kill than active bacteria because of their outer coating.
Curing a bacterial infection
The body reacts to disease-causing bacteria by increasing local blood flow (inflammation) and sending in cells from the immune system to attack and destroy the bacteria. Antibodies produced by the immune system attach to the bacteria and help in their destruction. They may also inactivate toxins produced by particular pathogens, for example tetanus and diphtheria.
Serious infections can be treated with antibiotics, which work by disrupting the bacterium’s metabolic processes, although antibiotic-resistant strains are starting to emerge. Immunisation is available to prevent many important bacterial diseases such as Hemophilus influenza Type b (Hib), tetanus and whooping cough..
Virus types
A virus is a miniscule pocket of protein that contains genetic material. If you placed a virus next to a bacterium, the virus would be dwarfed. For example, the polio virus is around 50 times smaller than a Streptococci bacterium, which itself is only 0.003mm long. Viruses can be described as either RNA or DNA viruses, according to which type of nucleic acid forms their core.
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