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Understand the Differences between Communicable Diseases

In this worksheet, students will distinguish between different pathogens and the diseases they cause.

Worksheet Overview

QUESTION 1 of 10

A smartphone

 

Did you know that a smartphone has more than 9,000 times more germs than a toilet seat?! Gross!

So what are germs? Germs often are referred to as microorganisms. Microorganisms are just that - organisms that are microscopic. Most microorganisms are harmless, however, some aren’t. Organisms that cause infectious diseases are called pathogens. There are different types of pathogens: bacteria, fungi, viruses and protists.

 

Image of bacteria, virus and fungi

 

Some diseases are communicable - they can be spread from organism to organism. Different pathogens spread in different ways. Some spread through direct contact, such as in bodily fluids (like blood) or through sex. Other pathogens spread through water or air, or in food.

Pathogens cause illness in three main ways:

 

Toxins: Toxins are harmful substances produced by the pathogen that poison the body’s tissues and enzymes. This makes us feel ill.

Reproduction:  Bacteria and viruses may reproduce inside the body. A rise in the number of pathogens can damage a cell, even causing it to burst. Some pathogens hijack resources that the cell needs to be able to survive.

Immune response: Sites of infection often become swollen, sore and hot as a result of increased blood flow, often making us feel rotten.

Let’s take a look at these disease-causing pathogens in more detail!

 

 Viruses

Viruses are the smallest pathogens. The genetic material of a virus is injected into the host cell. It then takes over the host cell by copying its DNA hundreds and thousands of times. The host cells eventually burst.

Some examples of viruses are measles, HIV and tobacco mosaic virus (TMV). Let's explore these further:

 

 

Name

Measles

 HIV

Tobacco mosaic virus (TMV)

Description

 Measles can cause complications, especially in young children which is why they are often vaccinated against it.

 

 

HIV stands for human immunodeficiency virus.

HIV sufferers might not know they are infected as symptoms may pass. However, the virus can cause the immune system to become so damaged that it can’t deal with other infections - this is called AIDS.

Tobacco mosaic virus (TMV) affects many species of plants, for example tobacco, tomato, peppers.

 It affects chloroplasts and causes a discolouration on leaves of plants which will affect the growth of the plant.

 

  measles rash      HIV virus       A tobacco plant

Symptoms

Fever, skin rash, cold-like symptoms

Flu-like illness

Discolouration on leaves of plants

Spreads

Inhalation of droplets from sneezes and coughs

Through bodily fluids like blood, often when drug users share needles or by sexual contact

Spreads through direct contact and contaminate

 

 

Bacteria

 

Image of bacteria

 

 Bacteria are larger than viruses. Bacteria replicate and divide very rapidly, allowing them to spread quickly.

 

 

Name

Salmonella

Gonorrhoea

Crown gall disease

Description

Salmonella causes food poisoning.

Taking antibiotics or using contraception such as condoms during sexual contact can prevent spreading.

Infects plants and fruits, such as grapes, nuts

Symptoms

Abdominal cramps, vomiting and diarrhoea

Causes a burning pain when urinating, thick discharge from the vagina or penis.

Causes galls or swollen tissues to grow on the plant stems or roots, preventing growth.

Spreads

 Bacteria in food or food prepared in unhygienic conditions

Sexually transmitted disease (STD) caused by a bacterium

Contaminated soil, water and farming tools

 

 

Fungi

Fungi come in different shapes and sizes. Some are microscopic, whereas others are quite large. Fungi have lots of uses in industry.

 

 

Name Rose black spot Barley powdery mildew
 Description

Image of roses

 

 Caused by a fungus which infects roses. Affects the growth of the plant as photosynthesis is reduced.

Image of barley fungus

 

Affects barley crops and the fungus can multiply quickly.

Symptoms

 

Purple or blacks spots develop on leaves, which turn yellow

 

Yellow spots, white fluffy growth on leaves and stems 

Spreads

Air or water, as well as through direct contact by gardeners

 

Fungal spores are spread in the air by the wind. 

 

 

Protists

Protists are usually microscopic and vary greatly from one another.

 

 

Name Malaria

Description

Malaria is spread by mosquitos which carry the plasmodium protist. Mosquitos suck blood containing the protists from an infected person. 

Infection can only be prevented by stopping individuals from being bitten. People sleep under mosquito nets and wear insect repellent to avoid bites. 

 Image of mosquito

 

Symptoms

 

 Fever, sweats and chills, headaches, vomiting and diarrhoea

Spreads

They pass the protist to other people they suck blood from. The mosquitos do not become ill and are called 'vectors' because they transmit the disease.


In the following activity, you will look at how pathogens such as viruses, bacteria, fungi and protists cause a variety of diseases.

Kate has a cold. The doctor says a pathogen has made her sick. 

 

What is meant by a pathogen?

A disease-causing microorganism

Germs

A disease

 

Pathogens can cause disease and illness.

 

What are the different types of pathogens? 

Bacteria

Viruses

Microorganisms

Protists

Fungi

Match the different diseases with the type of pathogen that causes it.

Plants, like animals, get infected by pathogens.

 

Match up the pathogens to the plant diseases

 

Image of bacteria, virus and fungi

Column A

Column B

Virus
Crown Gall Disease
Bacteria
Rose Black Spot
Fungus
Tobacco Mosaic

Salmonella, caused by bacteria, and HIV, a virus, spread in different ways.

 

How do salmonella and HIV spread?

Salmonella can spread in food

HIV can spread in food

Salmonella can spread through sexual intercourse

HIV can spread through sexual intercourse

Gonorrhoea and HIV are different human diseases. 

 

How are gonorrhoea and HIV similar?

 

Both can spread through sexual intercourse

Both are caused by bacteria

Both can spread by contaminated food

Barley powdery mildew and rose black spot are the names of diseases that affect plants.

 

What type of pathogen causes these two diseases?
 

Image of barley fungus  Image of roses

Which disease involves a mosquito as a vector? 

 

Image of mosquito

What is meant by the term vector?

A bacteria that causes a disease

An organism, like a mosquito that spreads a disease

A fungus that causes a disease

This disease often causes a rash and fever. It is a virus that spreads through the air in droplets that can be inhaled and children are often vaccinated against it.

 

What's the name of this disease?

 

Image of measles rash

Measles

Malaria

HIV

  • Question 1

Kate has a cold. The doctor says a pathogen has made her sick. 

 

What is meant by a pathogen?

CORRECT ANSWER
A disease-causing microorganism
EDDIE SAYS
Did this question confuse you a little? Germs are types of pathogens and a disease is caused by a pathogen, but the correct answer is the first option. Pathogens specifically refer to microorganisms that will cause disease or illness.
  • Question 2

 

Pathogens can cause disease and illness.

 

What are the different types of pathogens? 

CORRECT ANSWER
Bacteria
Viruses
Protists
Fungi
EDDIE SAYS
Were you tempted to tick them all?! Microorganisms would have been wrong though! Bacteria, viruses and protists are all microorganisms, but you needed to be more specific here and give the names of pathogens. Many fungi are microscopic but lots aren't, like the mushrooms you eat! So, you should have ticked four options - bacteria, viruses, protists and fungi.
  • Question 3

Match the different diseases with the type of pathogen that causes it.

CORRECT ANSWER
EDDIE SAYS
These are the key diseases you are most likely to be asked about in exams, so it's worth remembering which pathogen causes each disease!
  • Question 4

Plants, like animals, get infected by pathogens.

 

Match up the pathogens to the plant diseases

 

Image of bacteria, virus and fungi

CORRECT ANSWER

Column A

Column B

Virus
Tobacco Mosaic
Bacteria
Crown Gall Disease
Fungus
Rose Black Spot
EDDIE SAYS
How did you get on with this first question? These three plant diseases are the ones that are most commonly asked about in exam questions, but don't get thrown off when asked about other diseases - just apply what you know to the exam question!
  • Question 5

Salmonella, caused by bacteria, and HIV, a virus, spread in different ways.

 

How do salmonella and HIV spread?

CORRECT ANSWER
Salmonella can spread in food
HIV can spread through sexual intercourse
EDDIE SAYS
Pathogens can be spread in a variety of different ways - contaminated food and sharing bodily fluids are the two mentioned in this question. Salmonella causes food poisoning, so is most commonly found in food that's been under cooked or prepared in unhygienic conditions. HIV is often spread through exchanging bodily fluids by sharing needles when using drugs, or through sexual intercourse.
  • Question 6

Gonorrhoea and HIV are different human diseases. 

 

How are gonorrhoea and HIV similar?

 

CORRECT ANSWER
Both can spread through sexual intercourse
EDDIE SAYS
How did you get on with this one? At least you weren't asked to spell gonorrhoea! These two diseases are caused by different types of pathogens. Gonorrhoea is caused by bacteria, while HIV is a virus. The factor that they have in common is the way in which they are passed on to other people. Both of them are sexually transmitted diseases (STD).
  • Question 7

Barley powdery mildew and rose black spot are the names of diseases that affect plants.

 

What type of pathogen causes these two diseases?
 

Image of barley fungus  Image of roses

CORRECT ANSWER
Fungus
A fungus
Fungi
EDDIE SAYS
Both of these plant diseases are caused by a type of fungus. The fungus that causes these diseases will eventually prevent the growth of the plant.
  • Question 8

Which disease involves a mosquito as a vector? 

 

Image of mosquito

CORRECT ANSWER
Malaria
EDDIE SAYS
Mosquitos are vectors as they carry and spread the plasmodium protist, but without getting the disease themselves. Malaria is a killer across many parts of the world and scientists are always on the lookout for ways to protect people from being bitten by mosquitos or of controlling the spread of the insect. It has been said in the past that because of this, the mosquito is the world's most dangerous creature!
  • Question 9

What is meant by the term vector?

CORRECT ANSWER
An organism, like a mosquito that spreads a disease
EDDIE SAYS
A vector helps (unfortunately!) to spread disease but generally doesn't get the disease itself. The mosquito is the most obvious example since it carries the protist for malaria from host to host, without becoming ill itself. Another famous example is that of the rat flea in the seventeenth century, which carried bubonic plague without becoming ill with the disease itself.
  • Question 10

This disease often causes a rash and fever. It is a virus that spreads through the air in droplets that can be inhaled and children are often vaccinated against it.

 

What's the name of this disease?

 

Image of measles rash

CORRECT ANSWER
Measles
EDDIE SAYS
Did you get this one correct? HIV is a virus but it isn't spread through the air and malaria isn't caused by a virus but caused by a protist. This eliminates those two options and leaves us with measles - a virus that is carried through droplets in the air and causes a fever and a skin rash. Measles can be a very dangerous disease, especially in small children, and people do sometimes die from it. For this reason, it is recommended that parents get their children vaccinated against the disease when they are babies. Another activity completed - great stuff!
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