Chapter 12: Lesson 12.1 Communicable Diseases

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The term communicable means “able to be _______ .” If a disease is communicable, that means it can be transmitted to you. In other words, a _______  (also called an infectious disease) is a condition you can develop after coming into contact with living things or objects infected with the disease.

Twelve-year-old Dakota knows that _______  such as the flu are different from diseases such as heart disease that he might inherit from his parents or grandparents. A communicable disease is one that he can “catch.” When his friend Tavon came to school with the flu last month, for example, Dakota ended up sick, too. Dakota cannot, however, catch heart disease.

In this lesson, you will learn about the causes of communicable diseases. You will also learn about common communicable diseases that you may encounter in your life. Finally, you will learn possible treatment methods for communicable diseases.

Understanding Communicable Disease
Common living things that you can see are called _______ . You, your teacher, your _______ , and the trees outside are all examples of organisms. Many living things, however, are too small to see with the naked eye. These _______  are so small that you cannot even see them without the use of a microscope. Certain _______ , known as _______ , can cause communicable diseases (Figure 12.1). The term pathogen is a more scientific way of describing germs.

Pathogens are everywhere. They are so _______ , however, that you cannot see them. Pathogens are only _______  with a _______ , which magnifies them, or creates a bigger image of them. These microscopic organisms influence human lives in many ways. Pathogens include _______ .

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Bacteria
_______  are single-celled organisms that live in almost every place where life can thrive. Bacteria even _______  the _______ . In fact, so many bacteria live in the body that, of the several trillions of cells that make up your body, _______  are bacterial cells.

You may find it scary that bacteria are nearly everywhere. The good news is that most bacteria are helpful. For example, the bacteria found in your body help the _______  function efficiently. These bacteria also prevent harmful bacteria from thriving in your body. The bad news is that certain varieties of bacteria can cause different kinds of _______ . Some of these illnesses may be minor, while others can be quite serious and even deadly.

One type of bacteria that can cause disease is _______ . E. coli bacteria _______  in healthy people’s and animals’ _______ . There are different varieties of E. coli bacteria, however. Some varieties are harmless, while others can cause _______ . Exposure to harmful E. coli bacteria can occur from eating contaminated food, such as _______ , or drinking _______  (Figure 12.2). If you get sick from food poisoning, you may develop symptoms such as diarrhea, nausea, fever, and vomiting.

Another common type of bacteria, _______ , is present in about _______  of people’s _______ . The bacteria S. aureus often does not cause any harm. It can, however, spread to others through contact with contaminated hands. Sometimes, S. aureus causes _______  (skin and soft tissue infections). Anyone can get a staph infection, especially if you have a cut or scratch. People with chronic diseases and _______  are at greater risk of developing a more serious staph infection.

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Viruses
_______  are very different from _______  in your body. Viruses are much smaller than bacteria, and they are completely incapable of doing anything cells can do on their own. Viruses _______  on other cells for _______ . In fact, every virus must live inside a cell and use that cell’s resources and energy to grow and reproduce.

Viruses must be inside another living organism to thrive. Though viruses can stay on surfaces for a short time, they will die quickly if they do not find an organism in which to live. Once inside the body, a virus invades a person’s cells and multiplies quickly. 

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_______  (singular—fungus) are _______ , plant-like microorganisms that thrive in damp, warm places. These _______  are much more complex than _______  and _______ . Examples of fungi include _______ . A fungus cannot produce its own food, so it receives nourishment from plants, foods, and animals.

Like bacteria, few fungi _______ , and many are beneficial. For example, the mold known as Penicillium notatum makes the life-saving drug _______ , an antibiotic that controls bacterial infections. Other fungi, however, damage crops and stored foods. A few fungi cause infections, or mycoses, in humans. _______ , athlete’s foot, and jock itch are common fungal infections. People with weakened immune systems may be more likely to contract a fungal infection.

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Protozoa
_______  are _______  organisms that live nearly everywhere, and only a few cause diseases. Many kinds of protozoa form the basis of _______ , providing nutrients for other organisms. Certain protozoa, however, cause some of the world’s most feared diseases. These include _______ , a dangerous flu-like illness, and _______ , a severe intestinal infection. Protozoa thrive in _______ , and typically spread through contaminated water.

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Common Communicable Diseases
For a disease to be _______ , it must be able to _______  from one source to another. _______  causing communicable diseases may travel by various methods of transmission (Figure 12.4). A method of _______  is simply the way a disease gets from one organism or object to another. Methods of transmission are either _______ , depending on how the transmission occurs.

_______  is the movement of a pathogen from a person with a communicable disease to a susceptible person. A person who is susceptible to a disease is likely to be easily affected or harmed by it. A person who has a _______  may be more _______  to a disease than someone with a healthy immune system. 

_______  is the movement of a pathogen to a susceptible person through a source that acts only as a disease carrier. In this case, the carrier is simply moving a pathogen from one source to another. _______  diseases are a type of indirect transmission passed by mosquitoes, ticks, fleas, lice, and flies.

There are many examples of communicable diseases. You will likely encounter one or more communicable disease during your life. Some common communicable diseases include Lyme disease, West Nile virus disease, influenza, mononucleosis, tonsillitis, and conjunctivitis.

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Lyme Disease

_______  is a bacterial infection transmitted by infected ticks. Early signs and symptoms include a “bulls-eye” circular rash, _______ , headache, and _______ . Lyme disease can be treated with _______ . Untreated, the infection can cause inflammation of joints, heart, nerves, brain, and spinal cord; paralysis of face muscles; fluttering heartbeat; and shortness of breath. To prevent Lyme disease, use _______  and remove ticks promptly.

West Nile Virus (WNV) Disease

_______  disease (WNV) is a viral infection transmitted by _______ . Most people with WNV show no symptoms. Some people develop a _______ , body aches, joint pains, vomiting, diarrhea, or rash. Rarely, people develop severe WNV, which can cause convulsions, paralysis, _______ , and _______ . No vaccine or specific treatments for WNV are available. Medications can reduce fever and relieve some discomfort. People with severe WNV are often hospitalized. To prevent WNV, wear long sleeves and pants, use insect repellant, stay indoors when mosquitoes are most active, and eliminate sources of standing water.

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Tonsillitis
A virus or bacterium may cause _______ , which is an infection that affects the _______  (Figure 12.5). The tonsils usually _______  the body from _______ . Sometimes, however, the tonsils become infected.

Symptoms of _______  include _______ , fever, _______ , and voice changes. If you think you have tonsillitis, you should contact a doctor. Often, the best treatment for tonsillitis is getting lots of rest and drinking plenty of fluids.

Conjunctivitis
_______ , also known as _______ , is a viral or bacterial infection that causes inflammation of the conjunctiva in the eye. The conjunctiva is the tissue that _______  and inner surface of the eyelid. _______  of the conjunctiva results in itchiness and a red or pink appearance, which gives this condition its name (Figure 12.6).

If pinkeye is the result of a _______ , treatment typically involves the application of _______  to the affected eye. If the infection is viral, however, antibiotics will not work. A viral infection will run its course and go away as the body fights it.

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COVID-19
_______  is a serious and contagious _______  that first occurred in China during December 2019. The disease quickly spread to other countries and became a pandemic. Scientists soon discovered the disease was caused by a new virus they named _______ , also called _______  or novel coronavirus.

Signs and symptoms of COVID-19 include fever, cough, fatigue, muscle aches, nausea, and vomiting. These signs and symptoms may develop up to _______ . Severe illness is characterized by difficulty breathing, wheezing, and pneumonia. _______  primarily through contact with _______  produced by coughing, sneezing, breathing, and talking. A person may contract the virus by inhaling these droplets or touching them and then touching the nose, eyes, or mouth. People can transmit the virus before _______  or without developing symptoms at all.

In response to the pandemic, scientists worked to develop a COVID-19 vaccine, as well as other effective treatments. The FDA authorized the first COVID-19 vaccine for use in December 2020.

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Treating Communicable Diseases
Treatment methods for infections vary depending on the type of infection. To _______ , many doctors _______  such as penicillin or amoxicillin. Antibiotics are substances that target and kill pathogenic, or harmful, bacteria.

While antibiotics are generally very effective, some pathogenic bacteria have developed antibiotic resistance. This means certain antibiotics are ineffective against them. Antibiotic resistance is a growing issue. The best way to avoid contributing to it is to take antibiotics exactly as instructed by a doctor.

While antibiotics generally work well to treat bacterial infections, they do not work against viruses, fungi, and protozoa. _______  cure a _______ , but some medications can help treat the symptoms, such as a fever and body aches. The best treatment methods for viral infections include rest, good nutrition, and fluids to strengthen the body so it can fight the virus.

To treat _______ , doctors often prescribe _______  or creams that are applied directly to the infected area. Doctors may also prescribe medications to treat infections caused by protozoa. These medications are determined on a case-by-case basis, depending on the type of illness and the person’s symptoms and overall health.

Draggable item		Corresponding Item
COVID-19		condition someone can develop after coming into contact with living things or objects infected with the disease; also called infectious disease
tonsillitis		microorganisms that cause communicable diseases
conjunctivitis		substances that target and kill pathogenic bacteria
communicable disease		bacterial or viral infection that affects the tonsils
method of transmission		common viral infection that spreads through kissing or by sharing certain objects; also known as mono and the kissing disease
mononucleosis		contagious respiratory disease caused by the novel coronavirus; named a pandemic in January 2020
pathogens		viral infection of the respiratory system; also known as the flu
antibiotics		way a disease gets from one organism or object to another; may be direct or indirect
influenza		viral or bacterial infection that causes inflammation of part of the eye; also known as pinkeye

Chapter 12: Lesson 12.1 Communicable Diseases

Understanding Communicable Disease

Bacteria

Viruses

Protozoa

Common Communicable Diseases

Tonsillitis

Conjunctivitis

COVID-19

Treating Communicable Diseases

Understanding Communicable Disease

What are pathogens?

How can pathogens be seen?

What types of microorganisms can be pathogens?

What is the scientific term for germs that cause diseases?

Bacteria

Where do bacteria live inside the human body?

What do the bacteria in the body help with?

What percentage of cells in the body are bacterial cells?

What can drinking contaminated water lead to?

What can certain varieties of bacteria cause?

What are common symptoms of E. coli food poisoning?

Where do harmless E. coli bacteria typically live?

How can harmful E. coli bacteria enter the body?

Viruses

Where do viruses live inside the body to thrive?

Where do protozoa thrive?

What do viruses depend on for reproduction and growth?

What do viruses need to use from a cell to grow?

What happens to viruses if they do not find an organism?

What is a characteristic of fungi compared to bacteria and viruses?

Which of these is an example of a fungus?

What is a common fungal infection in humans?

In what conditions do fungi thrive?

Protozoa

What diseases can protozoa cause?

How do protozoa typically spread?

What is a characteristic of protozoa?

Common Communicable Diseases

How is direct transmission different from indirect transmission?

What is a susceptible person in terms of communicable diseases?

How are vector-borne diseases transmitted?

What is the defining characteristic of indirect transmission?

What is a common early sign of Lyme disease?

How can you prevent Lyme disease?

What can happen if Lyme disease is untreated?

How is Lyme disease treated?

Which of the following is a symptom of West Nile virus?

What can help prevent West Nile virus?

What can severe West Nile virus cause?

Tonsillitis

Conjunctivitis

COVID-19

Treating Communicable Diseases