Download Introductory Video – Infectious Disease Chapter 13: Preventing

Unit 5
Lesson 5.2 Notes
Introductory Video – Infectious Disease
Chapter 13: Preventing Infectious Disease
Section 1: What are Infectious Diseases?
Vocabulary:






Infectious disease: any disease that is caused by an agent that has invaded the body
pathogen: any agent that causes disease
bacteria: tiny, single-celled organisms, some of which can cause disease
virus: a tiny disease-causing particle that consists of genetic material and a protein coat
fungus: an organism that absorbs and uses nutrients of living or dead organisms
antibiotic resistance: a condition in which bacteria can no longer be killed by a
particular antibiotic
What Causes Infectious Diseases?




Infectious disease - Any disease that is caused by an agent that has invaded the body
May be passed form a person to another person, from food or water, from animals, or
from something in the environment
Ex: colds, the flu, head lice, tuberculosis (TB)
Caused by pathogens – any agent that causes disease
Bacteria



Bacteria – tiny, single-celled organisms, some of which can cause disease
o Too small to be seen without a microscope
o Live everywhere on Earth (even frozen Arctic and boiling waters of hot springs)
You have more than 300 kinds of bacteria living in your mouth, but most are harmless
and many are helpful!
o Ex: bacteria living in intestines make vitamins that you need to live
Some bacteria make you sick when they grow inside the body
o Give off poisons
o Damage cells
o Ex: tuberculosis, tetanus, sinus infections
Viruses



Viruses – tiny disease-causing particles made up of genetic material and a protein coat
o Smaller than bacteria
Genetic material in the virus contains the instructions for making more viruses
o Survive and replicate only inside living cells
o Reproduce by taking control of body cells and forcing them to make new viruses
o Viruses escape from cells and seek out other cells to attack
Ex: colds, flu, measles, AIDS, severe acute respiratory disease (SARS)
Fungi


Fungi – organisms that absorb and use the nutrients of living or dead organisms
Some fungi cause disease
o Ex: athlete’s foot – a fungus that lives and feeds on your feet
o Ex: ringworm – a fungus that leaves a scaly, circular rash
Protozoans


Protozoans – single-celled, microscopic organisms
o Larger and more complex than bacteria
Account for diseases that are leading causes of death throughout some parts of the world
o Ex: malaria (kills approx.. 1 mill people each year in tropical countries)
Parasites



Animal parasites – get their energy and nutrients by feeding on other living things
Animal parasites cause a large number of diseases throughout the world
o Most infectious disease in the US is from bacteria, viruses, fungi, protozoans
Ex: head lice, tapeworms, roundworms
How Are Infectious Diseases Spread?


Virus is present before you show symptoms
Infectious diseases spread in 4 main ways
Person to Person


When you sneeze / cough you send thousands of tiny drops of saliva and mucus into the
air
o Drops can remain in the air for a while and carry many pathogens with them
o Anyone who breathes in one of these infected drops can become sick from the
pathogens
o Anyone who touches anything the drops fall on (e.g. a book) can become infected
by the pathogens
 Ex: flu, colds, measles
Also spread by kissing, drinking from the same glass, sexual contact
o Ex: mononucleosis (aka “kissing disease”) spread through person-to-person
contact; can also be spread through sharing food, drinking from same cup
Food and Water



Foodborne diseases are often spread when pathogens from an infected person or animal
contaminate food
o This is why people who work with food must wash hands
Foodborne disease can also be spread when food is contaminated
o Ex: meat from infected animals may also contain eggs of parasitic worms
o Ex: hepatitis A and botulism
In the US, tap water is safe, but you need to purify lake and stream water
o Water can become contaminated if it’s exposed to sewage or animal wastes that
have not been treated.
o Purify water by boiling it, using water purification tablets, or a filtration system
o Diseases include: typhoid, cholera, giardiasis, dysentery
Environment


Pathogens are present on most of the objects around you
Many pathogens cannot live outside the human body, but some are tough and can survive
on objects in the environment
o Ex: on your phone, on money, in soil and can enter your body through a cut (e.g.
tetanus)
Animals



Many pathogens live in or on animals’ bodies and can carry diseases from one person to
another
o Ex: ringworm can be
contracted by petting a dog
or cat that has the fungus
Mosquitoes carry a pathogen that
causes malaria, yellow fever,
encephalitis
Ticks carry Lyme disease, Rocky
Mountain spotted fever (bacterial
diseases)
How Are Infectious Diseases Treated?

Each pathogen is treated in its own way
Treating Bacterial Diseases


Antibiotics – medicines used to kill or slow the growth of
bacteria
o Before antibiotics, even a small cut could lead to a deadly
bacterial infection
o Prevent the growth
and division of
bacterial cells,
causing them to die
o E.g. penicillin,
tetracycline,
streptomycin
o Can’t be used to
treat viruses (not for
colds or other viral
diseases)
Antibiotic resistance – a
condition in which bacteria
can no longer be killed by a
particular antibiotic (caused
by improper use of an
antibiotic)
o Today, people are
dying from infections that would have been easy to treat 10-15 years ago
o Prevent antibiotic resistance by not taking antibiotics if you have a viral disease
and using follow the prescription and use all your medication when prescribed an
antibacterial
Treating Viral Diseases



There is less known about how to destroy viruses than bacteria
Viruses do not grow as living cells, so viral infections can’t be treated with the same
medications as bacterial infections
Most antiviral medications concentrate on relieving symptoms an stopping production of
viruses inside the human cells
o Must be taken early in illness to have an effect
Treating Fungal Infections



Usually not as common as bacterial or viral infections, but sometimes serious
Usually treated with OTC (over the counter) medicine (e.g. athlete’s foot)
Others require stronger prescriptions (e.g. candidiasis – yeast infection)
Treating Protozoan Infections


Prevention is best protection
Maintain good hygiene and sanitation

If you have a protozoan infection, see a doctor to receive treatment with prescription
medicines
Treating Parasitic Infections

Prevent infection of head lice by not sharing combs or wearing others’ clothes; usually
treated with medicated shampoos
Section 2: Protecting Yourself from Infectious Diseases
Vocabulary:





inflammation: a reaction to injury or infection that is characterized by pain, redness, and
swelling
lymphatic system: a network of vessels that carry a clear fluid called lymph through the
body
white blood cell: a blood cell whose primary job is to defend the body against disease
vaccine: a substance usually prepared from killed or weakened pathogens or from genetic
material and that is introduced into body to produce immunity
symptom: a change that a person notices in his/her body or mind and that is caused by a
disease of disorder
How Your Body Fights Disease


body fights disease in many ways
o uses skin and chemicals to fight pathogens
o has specialized defenses, like inflammatory response and immune system
body is able to protect itself from pathogens
Physical Barriers





infection is not easy:
o pathogens must enter body, start growing, cause damage
body’s first line of defense helps stop pathogens from entering the body
skin – uses chemicals (e.g. sweat, oil that kill pathogens on skin)
o repairs and rebuilds itself quickly (e.g. closing cuts that pathogens could get
through)
mucous membranes – soft tissues that line the nose, mouth, throat, digestive tract,
urethra, vagina are all mucous membranes
o form a barrier to pathogens
o make a slimy material called mucus, which traps pathogens
 e.g. bacteria that you breathe in may get caught in the mucus lining the
tubes that carry air to the lungs; cilia (tiny, hairlike structures, grow from
the lining of these tubes) move mucus and bacteria to the back of the
throat where it’s swallowed and destroyed in the stomach
chemicals – chemicals made by your body
destroy pathogens
o e.g. sweat is acidic and inhibits the
growth of bacteria
o e.g. stomach secretes acids that not only
help you digest food but also kill bacteria
o e.g. tears contain a protein that kills
bacteria
Inflammatory Response


sometimes pathogens are able to cross the protective barriers that are your skin and
mucous membranes
o e.g. when you cut or burn yourself
o inflammation – reaction to injury or infection that is characterized by pain,
redness, swelling; it’s how your body protects itself from pathogens
protective barriers are broken and part of body becomes infected, area around injury
becomes inflamed and gets hot
o caused by small blood vessels that expand to bring more blood to the injured area
o sometimes pus (a yellowish substance) builds up around the injury
 pus includes dead and injured body cells that were fighting the bacteria
and dead and injured bacteria
o inflammatory response shows that your body is attacking pathogens
Immune System





immune system is made up of certain types of blood cells and certain proteins called
antibodies
o blood cells and antibodies move through the blood vessels and are within your
organs
lymphatic system - a network of vessels that carry a clear fluid called lymph throughout
the body
o infection-fighting cells move through the lymphatic system
o lymphatic system picks up fluid from all over the body and sweeps up bacteria or
viruses and carries them to your lymph nodes (feel in neck just between your ears
and jaw)
 lymph nodes are filled with white blood cells that scan the lymph for
pathogens
 white blood cells – cells in the blood whose primary job is to defend the
body against disease
 white blood cells produce antibodies that bind to specific
pathogens and warn other white blood cells to destroy the
pathogens
 when you’re sick, lymph nodes swell b/c of the growing number of white
blood cells fighting the infection
immune systems defenses take time to defeat pathogens
cells of immune system typically attack a specific pathogen
body’s other defenses (skin, mucus membranes, inflammation) react to and fight any
pathogen
What You Can Do to Stay Well






protect yourself – keep your body healthy
eat a healthy, balanced diet – lack of nutrients can weaken immune system
drink water – 8-10 glasses per day to keep immune system working
reduce stress – occasional stress is okay, but stress lasting weeks or months can weaken
immune system and leave you vulnerable to illnesses and colds
exercise regularly – at least 60 minutes per day
get regular medical checkups – prevent you from getting sick


avoid close contact with sick people – wash your hands, don’t share personal items
sleep – keeps body functioning
Get Vaccinated



vaccines – substances that are usually prepared from killed or weakened pathogens or
from genetic material that is introduced into a body to produce immunity
o when a vaccine is injected, the immune system responds to the vaccine material
by making white blood cells called memory cells.
o In the future, if the pathogen for the vaccine enters the body, the memory cells
and their antibodies fight the pathogen before it can cause disease
Boosters may be needed – extra doses of a vaccine that help the body maintain the
production of memory cells for a certain disease
You can also be immunized for diseases that develop new strains, like the flu
o But you need to get a vaccination each year when there’s a new strain
What to Do When Your Are Sick
Symptoms of Infection



Symptoms – the changes that you notice in your body or mind that are caused by a
disease or disorder
o E.g. fever, rash, sore throat, headache, muscle aches, fatigue, tired eyes, nausea,
omitting, diarrhea
Some symptoms are caused by the pathogens
o E.g. salmonella bacteria in raw eggs or undercooked chicken and meats cause
diarrhea when they invade cells lining the intestine
Some symptoms are part of your body’s response to infection
o E.g. fever (an increase in temperature) is sometimes caused by the invading
microorganisms, but sometimes is a defense against pathogens
 E.g. some bacteria can’t survive at higher temperatures, so your body
temperature rises in an attempt to stunt their growth
Taking Care of Yourself




Stay home when you feel sick
Drink plenty of fluids
Follow doctor’s directions
Throw away tissues, wash your hands
How to Prevent the Spread of Disease
Get Vaccinated


Vaccination programs have been largely responsible for preventing the
spread of infectious diseases
Vaccines are important for fighting viral diseases because few drugs
can stop a virus once it has begun to reproduce inside the body
Keep Clean


Maintaining good hygiene is one of the best ways you can prevent
spread of disease (washes away bacteria)
Count to 10 while rubbing your hands with soap and then rinse well
Don't Share Personal Items


Don’t share toothbrushes
Don’t’ share food or drink
Cover Your Mouth!


When you sneeze or cough
Throw away tissues
Be On Guard Outdoors




Wear long sleeved shirts and pants in long grass
Use bug repellant
Avoid animals that are acting strangely
Avoid drinking / swimming in remote streams, rivers, lake waters
Section 3: Common Infectious Diseases
Vocabulary:




Meningitis: the inflammation of the membranes covering the brain and spinal cord
Salmonellosis: a bacterial infection of the digestive system, usually spread by eating
contaminated food
hepatitis: an inflammation of the liver
amebic dysentery: an inflammation of the intestine cause by ameba
Disease Affect Everybody
Common Bacterial Diseases



bacteria are everywhere
many bacteria prefer to lie in dark, warm, moist places (like our bodies) and they grow
quickly there
strep throat, sinus infection, food poisoning (from undercooked chicken) – all caused by
bacteria
o meningitis – an inflammation of the membranes covering the brain and spinal
cord; can also be caused by viruses or fungi or parasites
o salmonellosis – bacterial infection of the digestive system, usually spread by
eating contaminated foods
Common Viral Diseases


Colds and flu are often viral and can be handled by your body
Others (e.g. hepatitis) are more serious
Other Common Infections
Fungal Infections



Fungi are important source of food and drugs, but some can be harmful
o E.g. athletes foot, jock itch, ringworm
Occur most often when type of fungus contacts skin that is warm and moist
Skin can become itchy and red and lesions may appear


Prevent infection by keeping clothing dry
o Maintain good hygiene
OTC medicines to kill the fungus
Protozoan Infections



Most often found in water and soil
20,000 kinds of protozoa exist, but only a small number cause disease
o E.g. amebic dysentery, malaria, African sleeping sickness
o Amebic dysentery – an inflammation of the intestine caused by an ameba
(symptoms: nausea, diarrhea, fever)
Malaria – most serious and widespread protozoan infection –
o several million people are infected each year
o about 1 million people die each year from it
o Caused by a protozoan that is passed from one person to another by mosquitoes
o Symptoms: fever, chills, headache, fatigue, nausea
o Prevented and treated with antimalarial drugs
Parasitic Infections




Hookworms, flukes, pinworms, tapeworms can live in the body and cause disease
Lice, leeches, ticks, fleas can live on the body
Spread by
o eating infected food,
o drinking infected water,
o contact with infected soil,
o bitten by infected insects
body lice are most common parasitic infection in the US
o can be seen with the naked eye
o cause itchiness and sores on the head
o use OTC medications, wash linens, soak brushes in hot water and soap, vacuum
carpet and furniture
Working Toward a Healthy Future



international travel makes it easier to spread disease
everyone in the world must work together to fight disease
Centers for Disease Control and Prevention (CDC) and National Institutes of Health
(NIH)are watching for diseases that my enter the country
o Important to have public health system to prevent or manage an infectious disease
outbreak
o Some countries can afford / don’t have resources for this, so public health is a
problem in certain areas of the world
o Work to control / eliminate diseases (e.g. measles, mumps, rubella, polio)
o Small pox has been eradicated in nature
Web Resources
Infections
National Foundation for Infectious Disease
InternetMedicine.com