Human Disease And Prevention


Human Disease And Prevention

For All Zoology Study Material PDF –  Click Here 

For All Subject Study Materials – Click Here

The diseases can be simply defined as a disturbance in the normal functioning of the body, among which few affects only to the particular organ system and some affect the entire body of an organism. There are numerous diseases which vary in their signs, symptoms, and causes. Pathology is the branch of medicines which mainly deals with the study of disease, the nature of diseases, its cure, diagnosis, etc.

Let us study certain communicable human diseases along with its causes and preventions.

Communicable Disease

A disease, which spreads from one person to another person, is termed as the communicable disease. It is also referred as infectious diseases or transmissible diseases.

Cause Of Communicable Disease

The agents causing communicable diseases include Virus, Bacteria, protozoa, and Fungi.


These microbes are small infectious agents which are present in food, air and in the water. They penetrate very easily into our body through the mouth, nose, cuts, injuries, scratches on the skin from the environment (from the soil, water, and air) and other infectious agents and causes severe infections which may also lead to the person’s death. The viral infections can be easily transmitted from person to person.

AIDS, Polio, Measles, Influenza are a few examples of infections caused by a virus.


There are millions and billions of beneficial and harmful bacteria present all around us. Few among them are present both inside and outside our body always, by protecting our body from the disease-causing microbes. These bacteria are called as beneficial bacteria. The other group of bacteria, cause harm by entering into our body. These bacteria generally, engulf, reproduce kill the protective bacteria and cause harm to the host cells by releasing toxins. Tuberculosis, Whooping cough, Typhoid, Cholera, are few examples of infections caused by bacteria.


They are single-celled, microscopic, eukaryotic organisms. Malaria and other immune system disorders are few examples of infections caused by the protozoan.


They are threadlike parasites, which cannot synthesize their food and feeds on other organic material in which they live in. Ringworm, Athlete’s foot are a few examples of infections caused by fungi.

There are other agents, who act as a carrier or vectors and they carry the disease-causing microorganisms and spread from one person to another person. These vectors include mosquitoes, rats, house flies, etc.

Control and Prevention Of Communicable Disease

Listed below are few precautions, which should be carried to avoid infection and other spreading diseases.

  • Drink only boiled and filtered water.
  • Maintain a proper hygiene in a food which we eat.
  • Maintain cleanliness around us.
  • Keep our body clean and tidy by having the regular bath.
  • Wear clean and ironed clothes.
  • Avoid the entry of vectors like mosquitoes, rats, house flies, cockroaches by spraying insecticides.
  • Disinfectants and other antiseptics can be used to destroy the microbes.
  • Fish plays a vital role in destroying mosquitoes and their larvae by eating them. So by introducing fish aquarium in our home, we can prevent mosquitoes from transmitting diseases.

There are many diseases which develop from the environmental problems, through nutrition deficiency, blood-related issues, chromosomal disorders, and so on.

Infectious Disease

Infectious diseases are a disorderliness that occurs due to the pathogenic microorganisms namely virus, bacteria, fungi, and parasite. These infectious diseases can either be communicable or non-communicable disease or it can be transmitted by animals or even by bites of animals or insects.

As mentioned earlier infectious diseases results from infection, agents responsible for causing this infection include viroids, nematodes, prion, arthropods namely mites and fleas and macroparasites such as helminths and tapeworms. It occurs when there is an invasion of an organism’s into the body cells and tissue with infection-causing agent involving the reaction of the host tissues to this organisms and due to the toxins that they produce.

List of Infectious Disease

  • Anthrax.
  • Burkholderia pseudo mallei.
  • Diphtheria.
  • Enterovirus Infection.
  • Granuloma inguinale.
  • Lead Poisoning.
  • Measles.
  • Mumps.
  • Rabies.
  • Severe Acute Respiratory Syndrome.
  • Smallpox.
  • Typhoid Fever.
  • Yellow Fever.
  • Yersinia.
  • Hepatitis C: It is not acute. It is a chronic disease.
  • Hepatitis B: It is caused due to inflammation of the liver which in turn causes jaundice, fatigue and in prolonged time it may also cause liver cancer.
  • Malaria: Caused due to a mosquito bite. It can be deadly if not treated for a prolonged time.
  • Dengue: It is caused by a particular type of mosquito. In rare cases, it leads to death, but it usually causes fever, headache and joints pain.
  • Tuberculosis: It causes coughing and chest pain due to the bacteria that are found in lungs. It may also result in different kind of side effects.

Prevention of Infectious Disease

Some of the practical ways for preventing the infection are listed below:

  • Maintaining the proper hand hygiene.
  • Use of antibiotics.
  • Keeping your kitchen clean by washing utensils, dishes, cooking area before and after preparing each food.
  • Vaccination – one of the most effective ways.
  • Maintain hygiene both in the bathroom and in the toilet area.
  • Avoid sharing personal belongings such as a razor, drinking glass, toothbrush, comb, etc.
  • Do not travel or go to work when you fall ill.
  • While visiting patients in hospitals, it is recommended to wear a mask, gown and if possible make use of sanitizing gels to prevent infection.
  • Acquired Diseases: They are acquired after the birth. They are grouped into two types. Communicable and noncommunicable.
  • The communicable disease is caused by certain microorganisms called pathogens (fungi, rickettsia, bacteria, viruses, protozoans, worms) which lead to infections. This disease spread from one person to another and is called communicable disease. Few examples include Cholera, chicken pox, malaria etc.
  • The non-communicable disease is caused by age, nutritional deficiency and sex of an individual, genetics and so on. Few examples include Hypertension, diabetes, and cancer. They do not spread to others and they restrain within a person who has developed them.


Cancer is caused by an uncertain growth of certain tissues in the body. It can be classified depending upon the type of the cell that has been affected initially. Tumors occur when a cancerous cell succeeds itself in dividing and making a new blood vessel to feed in a process namely angiogenesis. These cells also transport throughout the body by using a blood system, in turn, destroying the blood cells which are healthy. And this process is termed as an invasion.

No symptoms would occur when cancer begins. Some of the common types of cancer include breast cancer, colon cancer, cervical cancer, ovarian cancer, kidney cancer, liver cancer etc.

  • Degenerative or Organic Diseases: They are mainly caused by the malfunctioning of vital organs in our body. For example heart disease or cardiovascular disease.

Heart Disease

It is caused due to excessive smoking, alcohol consumption and lack of exercise. Common disorders include hypertensive heart disease, inflammatory heart diseases, cerebrovascular disease, valvular heart disease, ischemic heart disease and heart failure.

  • Symptoms – sweating, weakness, nausea, difficulty in breathing and irregular heartbeats.
  • Allergies: An allergic reaction arises when the body becomes hypersensitive to a certain foreign substance called allergens that come into contact with the substance. Common allergens include dust, pollen, animal dander, mites, feathers, latex and also certain food products. The symptoms include coughing, sneezing, running nose, itchy and red eyes, skin rashes, and difficulty in breathing. One of the best examples of this allergic reaction is the Asthma.


Asthma is a chronic disease, mainly affects bronchi and bronchioles of the lungs. One of the factors responsible for this is airborne allergens.

Symptoms – Difficulty in breathing, wheezing, and cough.

  • Deficiency Diseases: They occur due to the deficiencies of hormones, minerals, nutrients, and vitamins. For example diabetes, goiter, kwashiorkor, beriberi etc.


It is an abnormal enlargement of the thyroid gland by blocking the esophagus or other organs of chest and neck. This causes difficulty in breathing and eating. Goiters are mainly caused by the Iodine deficiency in our body.

Blood Disease

Some blood disorders may lead to cancer and some may not. It can also be caused due to blood proteins or even mainly due to platelets, red blood cells, and white blood cells. They include bleeding disorders, low blood platelets count, eosinophilic disorders, leukemia, myeloma (cancer of plasma cells in bone marrow), Sickle Cell Anemia, Aplastic Anemia, Hemochromatosis and Von Miller and Disease (blood-clotting disorder).

Symptoms- Pale skin, swelling of lymph nodes, fever, bleeding, bruising, skin rashes, etc.