Infectious Diseases in Humans PDF

Infectious Diseases in Humans Learning Outcomes Candidates should be able to: (a) state that infectious diseases can be spread from person to person whereas non-infectious diseases cannot and identify examples of each (b) explain that infectious diseases are caused by pathogens such as ba...

Infectious Diseases in Humans Learning Outcomes Candidates should be able to: (a) state that infectious diseases can be spread from person to person whereas non-infectious diseases cannot and identify examples of each (b) explain that infectious diseases are caused by pathogens such as bacteria and viruses and can be spread from person to person through body fluids, food and water (knowledge of the structure of bacteria and viruses is not required) (c) state the signs and symptoms of: influenza – caused by the influenza virus pneumococcal disease – caused by the bacteria, pneumococcus Learning Outcomes (d) describe the transmission and methods to reduce the transmission of: influenza virus pneumococcus (e) state that vaccines contain an agent that resembles a pathogen and prevent infectious diseases by stimulating white blood cells to quickly produce antibodies when the pathogen invades (f) state that antibiotics kill bacteria and are ineffective against viruses (g) explain that the misuse and overuse of antibiotics may accelerate the emergence of antibiotic-resistant bacteria Infectious Diseases - Definitions Disease – a condition that causes the body to function less effectively. It produces signs and symptoms such as fever, coughing and weight loss. Infectious disease – disease caused by pathogens that can be passed on to others. Infection – occurs when a pathogen enters the body and begins to reproduce; may or may not lead to disease. Pathogen – a microorganism that causes a disease. Eg: bacteria and viruses Example of infectious diseases: Influenza, HIV, Pneumococcal disease Non- Infectious Diseases Cannot spread from person to person. Not caused by pathogens. May be inherited or caused by factors such as malnutrition, lifestyle choices or environmental factors like pollution. Example of non-infectious diseases: Liver cirrhosis due to excessive alcohol consumption, and _________________________________ _______________________________________________________ Transmission of Infectious Diseases Pathogens that cause infectious diseases can be transmitted in many ways.  Through droplets in the air  Through contaminated food or water  By direct contact  By animal vectors such as insects, birds, bats, etc.  Through droplets in the air Pathogens in droplets can be expelled into the air when an infected person coughs, sneezes or talks. When people in close proximity inhale these droplets, they will be infected. Example: By Direct Contact Spread through sexual contact during sexual intercourse Example: _______________________________________ Spread through by non-sexual contact such as breastfeeding, shaking hands or touching contaminated surfaces. Example: Hepatitis B, syphilis and HIV By Dirty water or unhygienic food preparation can lead to contamination of water or food with Contaminated pathogens, leading to water-borne and food- Water and borne diseases. Food Example: _______________________________________ Influenza- Infectious Disease Caused By Virus It is a disease that attacks the respiratory system. Although most people can recover quickly, it can result in complications such as pneumonia (lung infection) Types of influenza: A, B, C Transmission Through droplets in the air Through direct contact such as touching the contaminated surfaces and -VIRUS CAN SURVIVE then touching APPROX 2 TO 8 HRS the eyes, nose -18-72 HOUR and mouth. INCUBATION Methods to Reduce Transmission Get influenza vaccination. Take prescribed antiviral drugs. Maintain safe distance from an infected person to avoid inhaling droplets released by the person. If you are unwell, make sure to cover you mouth and nose when coughing or sneezing, and dispose of used tissue appropriately. When feeling unwell, wear a mask to minimise the spread of pathogens. wash your hands with soap and water, or use a disinfectant such as hand sanitiser. Avoid touching eyes, mouth and nose Pneumococcal Disease- Infectious Disease Caused By Bacteria A disease that can cause infection in different parts of the body, including lung infection, sepsis, inflammation in the brain and spinal cord membranes (meningitis) and blood infection Caused by pneumococcal bacteria (Streptococcus pneumoniae) Pneumococcal disease is a name for any infection caused by bacteria called Streptococcus pneumoniae, or pneumococcus.  Transmission of Pneumococcal Disease Through respiratory droplets (coughing, sneezing) Signs and Symptoms Fever Headache Vomitting Cough Chest pain Rapid breathing Methods to Reduce Transmission Get pneumococcal vaccination Take prescribe antibiotics Maintain safe distance from an infected person to avoid inhaling droplets released by the person. If you are unwell, make sure to cover you mouth and nose when coughing or sneezing, and dispose of used tissue appropriately. When feeling unwell, wear a mask to minimise the spread of pathogens. wash your hands with soap and water, or use a disinfectant such as hand sanitiser. Avoid touching eyes, mouth and nose Vaccines A vaccine contains an agent that resembles a pathogen and prevents infectious disease by stimulating white blood cells to quickly produce antibodies when the pathogen invades.  Pathogens carried specific proteins called antigens on their surfaces. Once they enter our body, white blood cells will identify their antigens and begin to produce specific antibodies that can bind to these antigens and destroy the  A vaccine can be administered orally or though injection. It contains an agent that resembles a pathogen. When the vaccine enters the body, the complementary antibodies of white blood cells bind to the antigens of the agent and stimulate the white blood cells to divide in order to produce more antibodies. These antibodies will then bind to the antigens and destroy all the agents. Some of the white blood cells will then remain in the bloodstream for a period of time. This allows them to respond readily to actual pathogens.  Antibodies are specific in action. They can destroy one type of pathogen and will not be effective against other types of pathogens. When a large number of people are vaccinated, fewer people will be easily infected with the disease. As a result, the spread of the disease will be reduced. In this way, people who are not vaccinated will also be protected from the disease because the chance of them to get infected will be greatly reduced. Antibiotics Antibiotics are drugs used to treat bacterial infection. They are chemical substances made by microorganisms. They kill or inhibit the growth of bacteria by: Weakening the bacterial cell wall, thus allowing water to enter the bacterial cell by osmosis and causing it to swell and burst. Inhibiting some enzymes, thereby inhibiting the growth of bacteria. Preventing ribosomes from making proteins and enzymes, thereby killing the bacteria. Breaking up bacterial cell membranes. Antibiotics are ineffective against viruses, like influenza virus, because viruses do not have cell walls, cell Antibiotic Resistance How Antibiotics Resistance Can Be Reduced Complete the full course of an antibiotics as prescribed by doctors. Use antibiotics only when necessary. Do not misuse or overuse antibiotics, for example, do not use antibiotics to treat non-bacterial infections.