Infectious Diseases

Infectious diseases happen when pathogens such as bacteria, parasites, viruses and even fungi spread from one person to another.

When a disease spreads, it usually spreads from person to person.


Bacteria is one pathogen that causes infectious diseases. As we have read, many bacteria are good and even help with food digestion, but some bacteria are bad, and it causes sickness.

Bacteria is a single-celled or unicellular organism, which means, it only has one cell.

Bacteria are so small that they must be looked at under a microscope. Sometimes when something is so small that it needs a microscope to be looked at, we call that a micro-organism.

Bacteria has been studied for many years, by many different scientists. One scientist named Anton Von Leeuwenhoek, is one of the first scientists to discover bacteria.

Since bacteria are so small, even if millions of them clump together, they cannot be seen without a microscope.

If bacteria are in its environment, it can divide quickly and often.

When this happens, bacteria can spread and if it is a disease-causing bacterium, this is what causes the spread to happen so quickly.

Bacteria are also known to be in many shapes, sizes and colors.

Bacteria are found all over the world, in every type of environment, in bathrooms, playrooms, homes, schools, restaurants and everywhere you can imagine.

Disease of Bacteria

Some of the disease that bacteria cause are E.coli, Staphylococcus, which is strep throat, MRSA, which is a sickness that cannot be fixed with antibiotics and more. Bacteria can be very dangerous.


A parasite is an organism that lives off of another organism. A parasite cannot get food or move by themselves and they have to have another organism just to survive.

Parasite Diseases

People can catch parasites in many, many ways. Some of these ways include eating food that was not cooked enough, drinking water that is bad or contaminated with the parasite, eating raw meat, walking barefoot, getting bit by certain insects, touching people that have a parasite.

Some examples of parasite diseases are Lyme Disease, this happens by being bitten by ticks that are infected, Malaria, this is caused by infected mosquitos, Hookworm, this is caused by eating undercooked, raw or food that is not handled right.

How to Prevent Parasite Diseases

In order to not catch a parasite disease, it is important to wash your hands, wash your food before it is cooked, drink filtered water, do not eat raw meat, do not touch your eyes, ears or noses if your hands are dirty.


A virus is an organism that has a nucleus and has protein. Some scientists called a virus living, while others call it a non-living organism. A virus cannot move on its own and can only live if it is attached to something living.

Spreading Viruses

Viruses are spread by being around people that have the virus. If a person coughs, blows their nose or sneezes, the virus can attach to you and cause you to be sick as well. Some viruses are also caused by insects.

Most viruses are contagious, and this means that you can catch them. They move quickly and so when a virus goes from person to person, people get sick quickly.

Who Do Viruses Affect?

Viruses affect people, but they also affect dogs, plants and bacteria.


Some common viruses that are contagious are influenza, which is the flu virus, Swine Flu, Chicken Pox, Rabies, Mumps, Polio, Smallpox, Shingles and even the common cold are caused by viruses.

Many people get sick and die of viruses, so it is important to wash hands and to keep yourself safe from catching a virus.


Fungi, as we have read, are single-celled, or multi-celled organisms. This means they can have one cell or many cells.

Fungus feed on matter and they do not make their own food. Fungus comes in many different shapes and sizes and even colors.

One thing that makes a Fungi stand out is that it has a nucleus and a cell wall, but the cell wall is made out of chitin instead of cellulose.

Fungi are interesting because they can be found anywhere, and they can grow on anything.

Some examples of fungi are mushrooms, molds and even yeast is a form of fungi.

Diseases of Fungi

Fungus infections are different than other diseases because most of the time a fungal infection is found on your skin.

Most of the time, fungus does not get in the skin but sometimes fungus can get in to a person’s lungs and their sinuses.

Most fungus infections happen on the skin and nails such as Athlete’s Foot, which is a fungus infection that affects your feet and makes them itchy, yeast infections, and nail fungus.

A person can catch nail fungus by walking barefoot where someone else that had the disease walked barefoot, or you can catch them from nail salons.

Facts About Infectious Diseases:

  • A pathogen is an organism that causes diseases.
  • When a white blood cell helps to fight infections, it is called phagocyte.
  • When a person’s body recognizes the sickness and fights it, it is called an immune response.
  • Our body has T-Cells. The T-Cells helps the body to know which pathogen the body has.
  • Our body also has B-Cells. B-Cells make protein and help to destroy pathogens.
  • Antibodies help our bodies to fight off infectious diseases.
  • HIV and AIDS is a virus that affects the immune system.
  • When our body is immune, it means that it destroys the pathogens before a disease happens.
  • Vaccination is when the body gets some of the pathogen so it can recognize it and fight it off.
  • Antibiotics cannot kill viruses, only bacteria.
  • Viruses and bacteria are similar because they both destroy good cells, and they both produce to cause harm.

What Did You Learn?

  • What is an infectious disease? An infectious disease is a disease that can be spread from one person, plant or animal, to another.
  • What are the main four categories of infectious diseases? The main four categories of infectious diseases are fungi, bacteria, viruses and parasites.
  • Are all bacteria bad? Not all bacteria are bad, some bacteria are useful to help digest food.
  • Can viruses be cured by antibiotics? Antibiotics cannot cure viruses, only bacteria.
  • Can people die from infectious diseases? Infectious diseases can make people sick or make them die.
  • Can we stop infectious diseases from spreading? Yes! People can stop infectious diseases from spreading by washing hands, covering mouth when someone sneezes, keeping your homes and where you are clean and sanitized and staying away from people that are sick. One important idea is to NEVER share a drink with someone.