Human Health and Disease

In Biology, Human Health and Disease is an essential chapter comprising information related to various diseases, their agents, body immunity, etc. Studying the entire chapter before an examination is time-consuming as students have to study other materials as well. So, a selective material on significant concepts of this chapter is always advantageous.

Here, you will find important notes of biology for NEET Human Health and Disease, which will assist you during the preparation of the same as well as for other examinations.

Kinds of Diseases

Human diseases fall under two categories:

  • Congenital: Condition present from the time of birth

  • Acquired: A disease that occurs in the course of one’s lifetime


Immunity refers to a body’s ability to fight and protect itself from the attack of infectious microorganisms or foreign bodies. It is of two kinds, such as –

  1. Innate Immunity

This immunity is available from the time of birth and provides barriers to the invasion of any external disease-causing agent. Moreover, there are four kinds of barriers present; these include – 

  • Physical barrier.

  • Physiological barrier.

  • Cellular barrier.

  • Cytokine barrier.

  1. Acquired Immunity

This kind of resistance is pathogen-specific, and an individual acquires it during his/her lifespan.

The following table represents several infectious diseases that are common in human beings, along with their symptoms and effects.

Disease/Test Name

Organism or Pathogen Responsible

Means of Infection



Widal Test or Typhoid Fever

Salmonella typhi

Contaminated water.

Persistent high fever, stomach pain, low appetite, headache and constipation.

Intestinal perforation and even death may occur.


Hemophilus influenzae and streptococcus pneumoniae 

Inhalation of aerosols or droplets released from a person with the infection, or by touching infected utensils.

Cough, headache, chills and fever.

Alveoli gets filled with fluid and cause respiratory issues.

Common Cold

Rhino viruses

Cough, sneeze and contaminated substances.

Nose blockage and discharge, dry throat, headache, cough.

Affects respiratory passage and nose.


P. vivax (Protozoan) and Plasmodium falciparum

Vector: Anopheles mosquito (female); through mosquito bite.

High fever accompanying chills.

Parasites increase in liver and attacks red blood cells.

Amoebic Dysentery or Amoebiasis

Entamoeba histolytica

Carrier: Houseflies;

Spreads through food contaminated by faecal matter.

Pain in abdomen, blood and mucous present in stool, constipation, cramps.

Affects the large intestine.


Ascarsis (Helminthes)

Contaminated fruits, vegetables, water.

An infected person releases faeces containing eggs of the parasite which infect soil.

Fever, muscle pain, anaemia, internal bleeding, etc.

Intestinal infestation.

Filariasis or Elephantiasis

Wuchereria bancrofti

Vector: Female mosquitos and black flies that suck blood.

Genital organs and lower limb inflammation.

Affects lymphatic vessels present in lower limbs.


Epidermophyton, trichophyton and microsporum

Spreads by soil and utilising an infected person’s clothes, towel or comb.

Scaly and dry lesions and body portion between toes, and groin becomes itchy.

Affects nail, skin and scalp.


Allergy takes place when an individual’s immune system retaliates to particular substances like pollen, medicines, foodstuff, etc. A human’s immune system can differentiate between foreign and self-molecules or bodies.

However, there are specific scenarios where a body strikes its own cells. As a result, it harms the body and is termed as an auto-immune disease. An example of such an effect is rheumatoid arthritis.

Do It Yourself

Widal test is done to rule out which disease?

a) Malaria   b) Diabetes   c) AIDS   d) Typhoid


Human Immuno Deficiency Virus (HIV) is responsible for causing AIDS. The first case of AIDS was reported in the year 1981. Moreover, the transfer of HIV in humans takes place mainly through the following:

  • Sexual relationship with a person who has HIV.

  • Sharing infected syringe or needle.

However, it must be noted that transmission of HIV does not occur through water or air, pets or insects, saliva, tears, sweat, kiss and sharing food, drinks or restrooms.


Cancer refers to the uncontrollable and abnormal multiplication of cells. These cells occupy and kill the neighbouring tissues, and the continuous increase of cancer cells gives rise to neoplasms or tumours. Moreover, tumours can be divided into two categories, like:

  • Benign Tumours

These tumours remain constricted to its original location and do not spread to other organs in the human body and are considered non-cancerous.

  • Malignant Tumours

Cells in malignant tumours increase rapidly. Also, they move beyond the surrounding tissues and get into lymph and blood. Due to this happening, it can reach other body parts. This is referred to as metastasis, and only malignant neoplasms are counted as cancerous.

Reasons for Cancer

In general, the actual cause or reason of cancer is yet to be understood. But multiple factors may favour the growth of cancer cells. These factors or agents are termed as carcinogens.

Here is A Tabular Depiction of Carcinogens And The Affecting Organs



Lungs and skin

Coal tar

Prostate gland

Cadmium oxide

Pleural membrane and lungs


Skin and lungs







Chromium and nickel compounds


Mustard gas



Urinary bladder

4 - aminobiphenyl and 2 - napthylamine

Alcohol and Drug Abuse

Drugs that are abused commonly include cannabinoids, coca alkaloids and opioids. Few drugs can be obtained from fungi and mostly from flowering plants. Opioid drugs tie with opioid receptors which exist in the human GI tract and CNS (Central Nervous System).

On the other hand, cannabinoids interact with cannabinoid receptors in the brain. Examples of such drugs are hashish, marijuana, and charas.

FAQ (Frequently Asked Questions)

1. What Are The Critical Concepts in Human Health And Disease Chapter?

The essential concepts in human health and disease are kinds of diseases, general infectious diseases, immunity, AIDS, cancer, etc.

2. What Are The Different Ways By Which Human Immunodeficiency Virus Transmit?

The various ways of virus transfer are through sexual contact, transfusion of blood of individuals suffering from infection and using same needle for more than one person.

3. What is The Treatment And Study of Neoplasms Called?

The field of study of neoplasm – benign and malignant is known as oncology.