Infectious Diseases Objectives Define infectious disease Understand the

Infectious Diseases

Objectives • 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)

Objectives (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.

What Is an Infectious Disease? An infectious disease is a disease that can spread easily from one person to another.

Chain of Infection • Method by which a pathogen transmits a disease • Six distinct links – – – Agent Reservoir Portal of exit Mode of transmission Portal of entry New host

Links in the Chain of Infection

Agent • 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.

Reservoir • 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.

Portal 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.

Mode 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.

Portal 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.

New Host • Sixth link in the chain of infection. • Includes people who can get sick when they become exposed to a disease-causing microorganism.

Methods of Transmission • Through contact • Through the air • By common vehicle and vector

Direct 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)

Indirect Contact • Indirect 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.

Airborne • 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.

Common 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.

Six Major Causes of Infectious Diseases • • • Bacteria Viruses Fungi Protozoa Parasitic worms Prions

Bacteria • Microscopic, single-celled organisms that can be found practically anywhere. • Three types, named for shape: – Cocci (spherical) – Bacilli (rodlike) – Spirilla (spiral) (continued)

Bacteria (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).

Viruses • Infectious 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).

Fungi • 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).

Protozoa • One-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).

Parasitic 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).

Prions • 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.

Controllable 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. – Heredity – Age – Environment

External 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.

Innate Immune System • Component 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)

Innate 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.

Acquired 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.

Common Infectious Diseases • • Common cold Influenza (flu) Bacterial meningitis Pertussis (whooping cough) Tuberculosis Mononucleosis (mono) Pneumonia West Nile virus

Common 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)

Common 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.

Influenza • • 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.

Meningitis • Meningitis 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.

Pertussis • Pertussis 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.

Tuberculosis • Tuberculosis 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.

Mononucleosis • 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.

Pneumonia • Pneumonia 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.

West Nile Virus • Transmitted 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.

Sexually Transmitted Infections • • HIV and AIDS Hepatitis B Syphilis Chlamydia Gonorrhea Genital herpes Genital warts Pelvic inflammatory disease (PID)

HIV 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.

Signs and Symptoms of Full-Blown AIDS • Profuse night sweats • Chills that last for several weeks • Fever higher than 100 °F (38 °C) that lasts for several weeks • Dry cough • Shortness of breath • Persistent diarrhea (continued)

Signs and Symptoms of Full-Blown AIDS (continued) • • • Lesions on the tongue or in the mouth Headaches Blurred vision Chronic fatigue Swollen lymph nodes Rapid weight loss

How HIV Is Transmitted • • • Sexual transmission Through infected blood From mother to child Through organ transplants Through the use of unsterilized medical equipment

Protection From HIV • Practice safe sex. • Do not share needles. • Do not receive blood overseas if you can help it. • Get tested for HIV.

Hepatitis B • Serious 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.

Symptoms of Hepatitis B • • • Nausea Fever Chills Fatigue Loss of appetite Dark urine Abdominal pain Jaundice Joint pain

Protection 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.

Syphilis • Caused by Treponema pallidum bacteria. • Can be treated with antibiotics. • Transmitted through direct contact with a syphilis sore.

Primary 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.

Secondary 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.

Tertiary Stage of Syphilis • The third stage is characterized by damage to the central nervous system. • Other effects include blindness, senility, dementia, and cardiovascular damage.

Chlamydia • Infection 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.

Symptoms of Chlamydia • Approximately 75% of infected women and 50% of infected men experience no signs or symptoms. • Women might experience the following: – – – Burning sensation when urinating Abnormal vaginal discharge Lower back and abdominal pain Bleeding between menstrual periods Painful intercourse • Men might experience the following: – Penile discharge – Burning sensation when urinating – Burning around the opening of the penis

Gonorrhea • 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.

Genital Herpes • Caused 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.

Genital 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.

Pelvic 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.

Protection 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.

Protection From Infectious Diseases: Hand Washing • Wash your hands often with soap and water. • Wash for at least 20 seconds.

Protection 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.