A communicable disease is a disease that spreads from one person or animal to another. Pathogens such as viruses, bacteria, and fungi cause these diseases.

This article will discuss what communicable diseases are, their symptoms, and how to avoid them.

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Communicable diseases can spread when people get close to each other.

A communicable disease is any disease that passes between people or animals. People sometimes refer to communicable diseases as “infectious” or “transmissible” diseases.

Pathogens, including bacteria, viruses, fungi, and protists, cause communicable diseases.

A person may develop a communicable disease after becoming infected by the pathogen. This may happen through:

  • direct contact with a person carrying the pathogen
  • contact with contaminated fluids, such as blood, mucus, or saliva
  • inhaling contaminated droplets from another person’s cough or sneeze
  • receiving a bite from an animal or insect carrying the pathogen
  • consuming contaminated water or foods

Once a pathogen has entered a person’s body, it will begin replicating. The individual may then begin to experience symptoms.

Some symptoms are a direct result of the pathogen damaging the body’s cells. Others are due to the body’s immune response to the infection.

Communicable diseases are usually mild, and symptoms pass after a few days. However, some can be serious and potentially life threatening.

Four main types of pathogens cause infection: Viruses, bacteria, fungi, and protists.


Viruses are tiny pathogens that contain genetic material. Unlike other pathogens, they lack the complex structure of a cell. To replicate, they must enter the cells of other living beings. Once inside, they use the cell’s machinery to make copies of themselves.

Some different viruses include:


Rhinoviruses are a group of viruses that are responsible for the common cold. Symptoms of a cold may include:

A person can catch a rhinovirus by inhaling contaminated droplets from the cough or sneeze of another person.

Similarly, rhinoviruses spread by people touching their nose, eyes, or mouth after touching items or surfaces that have come into contact with the virus.


Influenza viruses are infections that attack the respiratory system. Some potential symptoms include:

A person can catch influenza viruses in the same way they may catch rhinoviruses.


HIV attacks the immune system of its host. This makes the person vulnerable to other infections and diseases.

A person can contract HIV as a result of contact with blood or other body fluids containing the virus.

The symptoms of HIV may develop gradually and in stages. They can include:

The only way a person can be certain they have HIV is to have an HIV test.

Although there is no cure for HIV, medications can help to keep the virus under control. Without such treatment, HIV can develop into AIDS.


Bacteria are microscopic, single celled organisms. They exist in almost every environment on earth, including inside the human body.

Many bacteria are harmless, and some help the body to function. However, bacteria can also cause infections that damage the body.

Some different types of bacterial infection include:

Salmonella and Escherichia coli

Salmonella and Escherichia coli (E. coli) are two different types of bacteria that can infect the digestive system.

They typically spread through contaminated foods, such as uncooked meats, and unwashed fruits and vegetables.

Some symptoms of these infections include:


Tuberculosis (TB) is a bacterial infection that primarily attacks the lungs. It may cause the following symptoms:

A person can catch TB by inhaling tiny droplets or “aerosols” from the cough or sneeze of a person who has the infection. However, the American Lung Association state that while TB is contagious, it does not easily spread from person to person.


Fungi are a type of organism that includes yeasts, molds, and mushrooms. There are millions of different fungi, but only around 300 cause harmful illnesses.

Fungal infections can occur anywhere in the body, but they commonly affect the skin and mucus membranes. Some different types of fungal infection include:


Ringworm is a common fungal infection of the skin. The characteristic symptom of ringworm is a red or silver ring shaped rash. It may be dry, scaly, or itchy.

People may contract ringworm in the following ways through close contact with a person who has ringworm. Alternatively, they can catch it from sharing towels, bedding, or other personal items with a person who has ringworm.

Without treatment, ringworm may spread to other parts of the body.

Athlete’s foot

Athlete’s foot is a common fungal infection that affects the skin on the feet. It typically causes sore or itchy white patches between the toes.

People can contract athlete’s foot through direct contact with someone who has the fungus, or surfaces that have been in contact with the fungus.

For example, an individual might contract athlete’s foot after walking barefoot in locker rooms, showers, or swimming pools.


Protists are microscopic organisms that typically consist of a single cell.

Some protists are parasitic, meaning they live on or inside another organism and use the organism’s nutrients for their own survival. Parasitic protists can cause various diseases.

The protist Plasmodium causes the tropical disease malaria. The parasite can pass from person to person through mosquito bites.

Malaria causes symptoms such as:

  • fever and chills
  • headaches
  • vomiting
  • diarrhea
  • muscle pains

Without proper treatment, malaria can be life threatening.

People can reduce their risk of contracting or transmitting disease causing pathogens by following the steps below:

  • washing their hands thoroughly and regularly
  • disinfecting surfaces at home often, especially doorknobs and food areas
  • practicing good hygiene when preparing and handling food
  • avoiding eating spoiled food
  • avoiding touching wild animals
  • receiving available vaccinations
  • taking antimalarial medications when traveling where there is a malaria risk

Some communicable diseases cause only mild symptoms that disappear without treatment. Others may cause severe symptoms, or potentially life threatening complications.

The treatment for such diseases depends on whether they are bacterial, viral, or fungal.

Viral infections

Vaccines are a highly effective method for preventing specific viral infections.

When a person receives a vaccine, they are receiving a dead or inactive form of the virus. The immune system responds by producing antibodies capable of killing an active form of the virus in the future.

If a person already has a virus, they may require antiviral medications to keep the virus under control.

Bacterial infections

A person who has a bacterial infection may require a course of antibiotics to help control the infection. These drugs work by killing off the bacteria or preventing them from replicating.

Fungal infections

A severe or chronic fungal infection may require over-the-counter or prescription antifungal medications. These are available in both oral and topical forms.

Communicable diseases are diseases that can pass from person to person. The pathogens that cause these diseases can spread in various ways, such as through the air, contact with contaminated substances or surfaces, or from animal and insect bites.

Many communicable diseases cause mild symptoms that go away without treatment. Others require treatment to prevent them from becoming more serious.

There are steps a person can take to reduce their risk of contracting and transmitting disease causing pathogens. These include receiving available vaccinations, practicing regular hand washing, and maintaining good hygiene at home.