2Objectives Define infectious disease. Understand the chain of infection.Understand the transmission methods of infectious agents.Identify the six major causes of infectious diseases.Understand the difference between controllable and uncontrollable risk factors.(continued)
3Objectives (continued) Understand the components of the external defenses and immune system of the body.Identify common infectious diseases and their causes, symptoms, and treatments.Define acquired immunodeficiency syndrome (AIDS) and the virus that causes it.Identify ways to protect yourself from infectious diseases.
4What Is an Infectious Disease? An infectious disease is a disease that can spread easily from one person to another.
5Chain of Infection Method by which a pathogen transmits a disease Six distinct linksAgentReservoirPortal of exitMode of transmissionPortal of entryNew host
7Agent First link in the chain of infection. Includes any disease-causing microorganism.Also known as pathogens or germs.Can be bacteria, viruses, fungi, protozoa, parasitic worms, or prions.An example is the influenza virus.
8Reservoir Second link in the chain of infection. Optimal environment where an agent can live, grow, and reproduce.Often, the reservoir is the body of an infected person; other examples of reservoirs include animals and soil.Agents continue to live and grow in the reservoir before they’re transmitted to others.
9Portal of Exit Third link in the chain of infection. Route agents take out of the reservoirs on their way to causing disease in others.Main portals of exit are the respiratory, digestive, urinary, and reproductive systems, as well as blood.
10Mode of Transmission Fourth link in the chain of infection. Method that agents use to move from reservoirs through portals of exit into potential hosts.Modes of transmission include direct and indirect contact, air, and common vehicles.
11Portal of Entry Fifth link in the chain of infection. Three primary portals of entry are the respiratory system, the digestive system, and breaks in skin.Two secondary portals of entry include the genital tract and the conjunctiva.There are three ways for an agent to gain entry to a potential host:Agent can infect cells in one of the portals of entry.Agent can enter body through skin that has been broken through trauma, bite, or infection.Infection can be congenital.
12New Host Sixth link in the chain of infection. Includes people who can get sick when they become exposed to a disease-causing microorganism.
13Methods of Transmission Through contactThrough the airBy common vehicle and vector
14Direct Contact Easiest way for pathogens to infect someone Three types Person to person (kissing, sharing straws)Animal to person (petting a dog, scooping cat litter)Mother to unborn child (from placenta to fetus)
15Indirect ContactIndirect contact is another method of transmission of pathogens to humans.Disease-causing organisms can live on doorknobs, telephones, and computer keyboards.You can become infected if an infected person has used the equipment before you.
16Airborne Droplets and particles are airborne methods of transmission. Tuberculosis and influenza are two types of infectious diseases that have the ability to spread both through droplet and particle transmission.
17Common Vehicle and Vector Infectious diseases can spread through insect carriers and even through food.Insect carriers are often called vectors.Vectors can transmit germs to humans by landing on or biting them.Uncooked meat and unwashed fruits and vegetables are often carriers for germs, as is unclean, unpurified water.
18Six Major Causes of Infectious Diseases BacteriaVirusesFungiProtozoaParasitic wormsPrions
19BacteriaMicroscopic, single-celled organisms that can be found practically anywhere.Three types, named for shape:Cocci (spherical)Bacilli (rodlike)Spirilla (spiral)(continued)
20Bacteria (continued)Many types of bacteria can live in the body without causing harm.Examples include pertussis (Bordetella pertussis), Lyme disease (Borrelia burgdorferi), peptic ulcers (Helicobacter pylori), tuberculosis (Mycobacterium tuberculosis), and pneumonia (Mycoplasma).
21VirusesInfectious parasites made up of a protein shell that encloses either deoxyribonucleic acid (DNA) or ribonucleic acid (RNA).Can’t reproduce by themselves, so they’re dependent on other living beings for reproduction.Due to their unique makeup, diseases caused by viruses are among some of the most contagious.Examples include the common cold (rhinovirus), genital warts (human papillomaviruses), influenza (influenza A and B), chicken pox (varicella zoster), and genital herpes (herpes simplex 1 and 2).
22Fungi Single-celled or multicelled plant. Replicate by budding or making spores.Many fungal infections come from environmental exposure to the spores.Examples include yeast infections (Candida albicans), athlete’s foot (dermatophyte fungi), and histoplasmosis (Histoplasma capsulatum).
23ProtozoaOne-celled organisms that usually can live independently of a host.Transmitted by feces or contaminated water or food.Examples include giardiasis (Giardia lamblia), trichomoniasis (Trichomonas vaginalis), and amoebic dysentery (Entamoeba histolytica).
24Parasitic Worms Also known as helminths. Largest of the pathogens. Live on or in a host.Can infect people who unintentionally consume worm eggs either in food or water.Larvae can break through and burrow into the skin.Examples include pinworm infections (Enterobius vermicularis), hookworm infections (Necator americanus), and roundworm infections (Ascaris lumbricoides).
25Prions Consist solely of protein material but lack DNA and RNA. Responsible for the spread of bovine spongiform encephalopathy (BSE), or mad cow disease.Diseases caused by prions are usually characterized by spongelike holes in the brain, dementia, and weakness.
26Controllable and Uncontrollable Risk Factors Acquire and maintain a strong immune system to avoid diseases.Exercise daily.Eat a well-balanced diet.Get enough sleep.Don’t smoke or use illegal drugs; do limit alcohol consumption, manage stress, and get vaccines.Practice good hygiene.Some risk factors can’t be avoided.HeredityAgeEnvironment
27External Barriers First line of defense against invading pathogens. Include both physical and chemical barriers.Skin is one of the most important barriers.Mucous membranes, hair, and cilia are other examples of external physical barriers.Saliva and stomach acid are examples of external chemical barriers.
28Innate Immune SystemComponent of the immune system that is present from birth.Fast-response system designed to remove any foreign matter.Causes inflammation at the site where a pathogen breaches the external defenses of the body.(continued)
29Innate Immune System (continued) The inflammation causes redness, pain, warmth, or swelling.Helps the body identify bacteria and activates cells to clear dead cells.Identifies and removes foreign substances in the organs, tissues, blood, and lymph.
30Acquired Immune System Component of the immune system that grows as you are exposed to a variety of disease-causing pathogens.The two parts are active and passive immunity.Active immunity targets specific foreign particles. Vaccinations are considered part of the active immune system.Passive immunity is from another source, such as immunity from the mother passed through the placenta or breast milk.
31Common Infectious Diseases Common coldInfluenza (flu)Bacterial meningitisPertussis (whooping cough)TuberculosisMononucleosis (mono)PneumoniaWest Nile virus
32Common Cold Also known as acute rhinitis. Can be caused by more than 200 types of rhinoviruses.Very contagious viral infection that is generally spread by person-to-person contact.(continued)
33Common Cold (continued) Early symptoms include runny or stuffy nose, nasal discharge, mild muscle aches, and sore throat.Ways to alleviate symptoms:Drink plenty of fluids.Get plenty of rest.Eat well.Use over-the-counter medications to ease muscle aches.Gargle with salt water.Use lozenges.
34Influenza Caused by the influenza virus. Infection of the respiratory tract.Usually transmitted by droplets.Characterized by headaches, severe muscle aches, sudden onset fatigue and weakness, and sudden onset of a high fever, chills, sore throat, and cough.Get plenty of rest, drink lots of fluids, and use aspirin when needed.
35MeningitisMeningitis is inflammation of the meninges, the membranes covering the brain and spinal cord.Can be caused by bacteria or viruses.Viral meningitis is often mild, but bacterial meningitis requires immediate attention because it can be fatal.Symptoms of bacterial meningitis include sudden onset of a high fever, sudden onset of a severe headache, acute fatigue, nausea, and a stiff neck.A vaccine (Menactra) is now available for meningococcal meningitis and the other three types of bacterial meningitis.
36PertussisPertussis is an infection of the respiratory tract also known as whooping cough.Symptoms include runny nose, slight fever, and nasal congestion.Distinctive symptom is a dry cough, resulting in coughing bouts that can last for several minutes and that end with a whooping sound.Can be treated with antibiotics.
37TuberculosisTuberculosis is a chronic bacterial infection caused by Mycobacterium tuberculosis.Also known as consumption or white death.Spreads from person to person through the air when an infected person coughs, sneezes, or even speaks.Symptoms include fever, weight loss, weakness, night sweats, chest pain, coughing, and coughing of blood.Can be treated with antibiotics.
38Mononucleosis Known as kissing disease or mono. Caused by Epstein-Barr virus.Spread through contact with the saliva of an infected person.Symptoms are sore throat, fever, swollen glands, headache, chills, nausea, and severe and persistent fatigue and weakness.Requires at least 1 or 2 months of rest.Treatment involves getting lots of bed rest, eating a balanced diet, drinking adequate amounts of fluid, and using over-the-counter medications such as aspirin and lozenges.
39PneumoniaPneumonia is an infection of the lungs and lower respiratory tract.Caused by bacteria, viruses, or fungi.Most common form is bacterial pneumonia.Characteristics of pneumonia are high fever, severe chest pains, shortness of breath, chills, and a productive cough.
40West Nile VirusTransmitted by mosquitoes that have bitten wild birds—usually crows and jays—that serve as reservoirs for the virus.Signs and symptoms include headache, fever, diarrhea, nausea, vomiting, skin rash, backache, swollen lymph glands, and lack of appetite.Rarely, the virus can cause encephalitis or meningoencephalitis.
41Sexually Transmitted Infections HIV and AIDSHepatitis BSyphilisChlamydiaGonorrheaGenital herpesGenital wartsPelvic inflammatory disease (PID)
42HIV and AIDS AIDS stands for acquired immunodeficiency syndrome. The virus that causes AIDS is the human immunodeficiency virus (HIV).HIV damages the immune system, making it difficult for the body to fight off disease-causing organisms.AIDS usually has no signs or symptoms in the early stage.At later stages, signs and symptoms include swollen lymph nodes, diarrhea, weight loss, fever, cough, and shortness of breath.
43Signs and Symptoms of Full-Blown AIDS Profuse night sweatsChills that last for several weeksFever higher than 100 °F (38 °C) that lasts for several weeksDry coughShortness of breathPersistent diarrhea(continued)
44Signs and Symptoms of Full-Blown AIDS (continued) Lesions on the tongue or in the mouthHeadachesBlurred visionChronic fatigueSwollen lymph nodesRapid weight loss
45How HIV Is Transmitted Sexual transmission Through infected blood From mother to childThrough organ transplantsThrough the use of unsterilized medical equipment
46Protection From HIV Practice safe sex. Do not share needles. Do not receive blood overseas if you can help it.Get tested for HIV.
47Hepatitis BSerious liver disease caused by the hepatitis B virus (HBV).Transmitted from one person to another through sexual contact, through shared use of needles, and from mother to child during pregnancy.Can also spread through close nonsexual contact; by exposure to infected blood; and by contact with mucous membranes.
48Symptoms of Hepatitis B NauseaFeverChillsFatigueLoss of appetiteDark urineAbdominal painJaundiceJoint pain
49Protection From Hepatitis B Get vaccinated.Use latex condoms when engaging in sexual activity.Do not share needles or syringes.Make sure all needles and syringes are sterile if you are getting a tattoo or body piercing.
50Syphilis Caused by Treponema pallidum bacteria. Can be treated with antibiotics.Transmitted through direct contact with a syphilis sore.
51Primary Stage of Syphilis A chancre sore develops, usually at the site of the infection.In males, the sore is usually near the penis or scrotum.In females, the sore is usually on the cervix or vaginal wall.
52Secondary Stage of Syphilis This stage is characterized by white patches on the skin, lesions on mucous membranes, hair loss, fever, headache, fatigue, weight loss, and swollen lymph nodes.Lesions can appear 3 weeks to 1 year after the chancre sore has disappeared.
53Tertiary Stage of Syphilis The third stage is characterized by damage to the central nervous system.Other effects include blindness, senility, dementia, and cardiovascular damage.
54ChlamydiaInfection of the urogenital tract caused by the bacteria Chlamydia trachomatis.Transmitted from one infected person to another through oral, vaginal, or anal sex.Infected mothers can also pass the bacteria to their babies during vaginal childbirth.
55Symptoms of ChlamydiaApproximately 75% of infected women and 50% of infected men experience no signs or symptoms.Women might experience the following:Burning sensation when urinatingAbnormal vaginal dischargeLower back and abdominal painBleeding between menstrual periodsPainful intercourseMen might experience the following:Penile dischargeBurning around the opening of the penis
56Gonorrhea Caused by the bacteria Neisseria gonorrhoeae. Spread by contact through the mouth, vagina, penis, or anus or from infected mother to child during delivery.Affects the linings of the urethra, genital tract, pharynx, and rectum.Can be treated with antibiotics.
57Genital HerpesCaused by the herpes simplex virus types 1 (HSV-1) and 2 (HSV-2).Most cases caused by HSV-2.Enters the body through tiny breaks in the skin or mucous membranes through either sexual contact or skin-to-skin contact.Characterized by pain, itching, burning sensation when urinating, and sores in the genital area, along with headache, fever, muscle aches, and swollen lymph nodes in the groin.No cure is available.
58Genital Warts Caused by the human papillomavirus (HPV). Can be found in the skin of the penis, vulva, and anus; in the vagina, cervix, or rectum; or in the mouth or throat.Warts can appear as either flesh-colored bumps or have a cauliflower-like appearance and are soft, moist, and pink.Can cause itching in the genital area along with bleeding and pain during intercourse.No cure, but warts can be removed using medications or health care workers can surgically remove them.
59Pelvic Inflammatory Disease Infection of the female reproductive organs, including the uterus and fallopian tubes.PID is a frequent and serious complication from untreated sexually transmitted infections such as gonorrhea and chlamydia.Symptoms include painful intercourse, painful urination, heavy and odorous vaginal discharge, pain in the lower back and abdomen, and irregular menstrual bleeding.Can be treated with antibiotics.
60Protection From Infectious Diseases: Immunizations Make sure your vaccinations are up to date.It’s especially important for college students to receive the meningitis and HPV vaccinations.
61Protection From Infectious Diseases: Hand Washing Wash your hands often with soap and water.Wash for at least 20 seconds.
62Protection From Infectious Diseases: Safe Sex Practices Practice abstinence, if possible.Use latex condoms.Be in a long-term, mutually monogamous relationship.Avoid sexual activity with any partner whose sexual history you don’t know.Limit excessive use of alcohol or other drugs because such use can impair judgment, which could lead to risky sexual practices.