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What You Need to Know Essential Standard: 8.L.1 Understand the structure and hazards caused by agents of disease that effect living organisms. Clarifying Objective: 8.L.1.1 Summarize the basic characteristics of viruses, bacteria, fungi and parasites relating to the spread, treatment and prevention of disease. Students need to know: microbiology as a basic science explores microscopic organisms including viruses, bacteria, protozoa, parasites, and some fungi and algae. These organisms lack tissue differentiation, are unicellular, and exhibit diversity of form and size. viruses, bacteria, fungi and parasites may infect the human body and interfere with normal body functions. Some kinds of bacteria or fungi may infect the body to form colonies in preferred organs or tissues. - Viruses Viruses are non-living particles composed of a nucleic acid (DNA or RNA) and a protein coat. Viruses need a host cell to reproduce. Viruses invade healthy cells and use the enzymes and organelles of the host cell to make more viruses, usually killing those cells in the process. Viral diseases are among the most widespread illnesses in humans. These illnesses range from mild fevers to some forms of cancer and include several other severe and fatal diseases. Transmission of these illnesses varies; some are transmitted by human contact, while others are transmitted through water or an insect bite. Vaccines and some anti-viral drugs are used to control and prevent the spread of viral diseases. - Bacteria Bacteria are prokaryotic single-celled organisms. Bacteria can live in a variety of places (with oxygen, without oxygen, extreme hot, extreme cold). Bacteria reproduce through binary fission, a form of asexual reproduction. Under optimal conditions, bacteria can grow and divide extremely rapidly, and bacterial populations can double very quickly. Antibiotics are used to inhibit the growth of bacteria. Because antibiotics have been overused, many diseases that were once easy to treat are becoming more difficult to treat. Antibiotic resistance in bacteria occurs when mutant bacteria survive an antibiotic treatment and give rise to a resistant population. 1|Page - Fungi Fungi can sometimes attack the tissues of living plants and animals and cause disease. Fungal disease is a major concern for humans because fungi attack not only us but also our food sources, making fungi competitors with humans for nutrients. Mold spores can cause mild to serious allergies in some people. Billions of mold spores can become airborne and may then be inhaled, triggering an allergic reaction. - Parasites A parasite is an organism that feed on another individual, known as the host. They either live on or in their host’s body. Natural selection favors adaptations that allow a parasite to efficiently exploit its host. Parasites are usually specialized anatomically and physiologically. Tapeworms are so specialized for a parasitic lifestyle that they do not even have a digestive system. They live in the small intestine of their host and absorb nutrients directly through their skin. Infectious disease may also be caused by animal parasites, which may take up residence in the intestines, bloodstream, or tissues. BOTTOMLINE: Microbiology as a basic science explores microscopic organisms including viruses, bacteria, protozoa, parasites, and some fungi and algae. These organisms lack tissue differentiation, are unicellular, and exhibit diversity of form and size. Viruses, bacteria, fungi and parasites may infect the human body and interfere with normal body functions. A person can catch a cold many times because there are many varieties of cold viruses that cause similar symptoms. Viruses are not considered to be alive but they affect living things. Viruses need a host cell. AIDS, influenza, the common cold, polio, chicken pox, small pox, yellow fever, viral meningitis, West Nile and Ebola are caused by viruses. Rabies, Lyme Disease, bacterial meningitis, and Leprosy are caused by bacteria. Bacteria are very small organisms, usually consisting of one cell, that lack chlorophyll. Except for viruses, they are the smallest living things on Earth. Bacteria are found everywhere, in the air, soil, water, and inside of your body and on your skin. They tend to multiply very rapidly under favorable conditions, forming colonies of millions or even billions of organisms within a space as small as a drop of water. Bacteria are generally classified into three groups based on their shape: spherical, rodlike, spiral or corkscrew. We have antibiotics to help with bacterial infections and vaccines to help with taking care of viruses that cause infections. 2|Page Essential Standard: 8.L.1 Understand the structure and hazards caused by agents of disease that effect living organisms. Clarifying Objective: 8.L.1.2 Explain the difference between epidemic and pandemic as it relates to the spread, treatment and prevention of disease. Students need to know: a disease outbreak happens when a disease occurs in greater numbers than expected in a community or region, or during a season. - An outbreak may occur in one community or even extend to several countries. It can last from days to years. Sometimes a single case of a contagious disease is considered an outbreak. This may be true if it is an unknown disease, is new to a community, or has been absent from a population for a long time. An outbreak can be considered as an epidemic or pandemic. epidemic and pandemic are similar terms that refer to the spread of infectious diseases among a population. - There are two main differences between epidemic and pandemic. The term pandemic normally is used to indicate a far higher number of people affected than an epidemic. Pandemic also refers to a much larger region being affected. In the most extreme case, the entire global population would be affected by a pandemic. the terms epidemic and pandemic usually refer to the rate of infection, the area that is affected or both. - An epidemic is defined as an illness or health-related issue that is showing up in more cases than would normally be expected. It occurs when an infectious disease spreads rapidly to many people. In 2003, the severe acute respiratory syndrome (SARS) epidemic took the lives of nearly 800 people worldwide. in the case of a pandemic , even more of the population is affected than in an epidemic. - A pandemic typically is in a widespread area (usually worldwide) rather than being confined to a particular location or region and affect global populations. An epidemic is not worldwide. For example, malaria can reach epidemic levels in regions of Africa but is not a threat globally. Whereas a flu strain can begin locally (epidemic) but eventually spread globally (pandemic). This is not unusual for a new virus, because if people have not been exposed to the virus before, their immune systems are not ready to fight it off, and more people become ill. Swine flu started in Mexico City where it was feared to lead to epidemic proportions in North America, now that the flu has been 3|Page found in New Zealand, Israel, Scotland and many other countries, it has become pandemic. The 1918 Spanish flu and the Black Plague are extreme examples of pandemics. Keep in mind, though, that a pandemic doesn't necessarily mean millions of deaths-it means a geographically widespread epidemic. influenza pandemics have occurred more than once. - Spanish influenza killed 40-50 million people in 1918. The Asian influenza killed 2 million people in 1957. The Hong Kong influenza killed 1 million people in 1968. An influenza pandemic occurs when: A new subtype of virus arises. This means humans have little or no immunity to it; therefore, everyone is at risk. The virus spreads easily from person to person, such as through sneezing or coughing. The virus begins to cause serious illness worldwide. With past flu pandemics, the virus reached all parts of the globe within six to nine months. With the speed of air travel today, public health experts believe an influenza pandemic could spread much more quickly. A pandemic can occur in waves. And all parts of the world may not be affected at the same time. Teacher Note: It is not necessary for students to know specific examples of epidemics and pandemics. Examples provided are for teaching purposes only. Vectors are mechanisms (other than a person) that spread disease without getting sick itself. Rats, ticks, mosquitoes, and soil are examples of vectors. An infectious disease is one that can be passed from one generation to another. Scientists study microbial pathogens (disease causing agents), to find methods for prevention and treatment of disease. Improvements in public health depend upon state-of-the-art biomedical research to explain how microbes cause infectious diseases in both plants and animals. To analyze data, scientists use various techniques and strategies including computer modeling, cell culture, animal models, and clinical trials in humans. Safe handling and hygiene as well as various antimicrobial chemicals can be used to reduce the risk of and the treatment of these infections. Industrial microbiology involves quality control in preventing growth and contamination of products leading to food spoilage, and the production of pharmaceuticals. The health of humans and earth depends on microbes. An epidemic is an outbreak of a disease that affects a disproportionately large number of individuals within a population, community or region at the same time (example-typhoid). Pandemic is an epidemic of an infectious disease that is spreading through human populations across a large region, continent or even worldwide (examples smallpox, tuberculosis, flu of 2009). BOTTOMLINE: 4|Page