Human Health and Disease

Health And Its Failure

In common language, health is often perceived as simply the absence of disease or physical fitness. However, a more comprehensive understanding of health goes beyond this narrow view.

The Significance Of ‘health’

According to the World Health Organization (WHO), health is defined as a state of complete physical, mental, and social well-being, and not merely the absence of disease or infirmity.

Being healthy means an individual is able to function well physically, mentally, and socially.
Health is not a static condition; it is a dynamic state that varies over time and is influenced by various factors.

Personal And Community Issues Both Matter For Health

An individual's health is not solely a personal matter; it is influenced by and also affects the community they live in. Therefore, both personal and public (community) issues are important for health.

Personal health: Refers to an individual's own health status, influenced by lifestyle choices (diet, exercise, hygiene), genetic factors, and access to healthcare. Maintaining personal health involves individual responsibility.
Community health (Public health): Refers to the health of the population as a whole. It is influenced by factors like sanitation, availability of clean drinking water, pollution control, disease prevention programmes, public healthcare infrastructure, and social environment.

Individual health is affected by the community environment. For example, if the community has poor sanitation, an individual's risk of infectious diseases increases, regardless of their personal hygiene. Conversely, the health choices of individuals (e.g., vaccination rates, spread of infectious diseases) impact community health.

Maintaining good health for everyone requires addressing both individual behaviours and community-level issues like providing clean surroundings and a socio-economic environment conducive to health.

Distinctions Between ‘healthy’ And ‘disease-free’

Healthy: A state of complete physical, mental, and social well-being. A healthy person is physically fit, mentally balanced, and interacts well socially.
Disease-free: Absence of a specific disease. A person may be disease-free but may not be considered 'healthy' in the broader sense (e.g., a person without any diagnosed disease but suffering from severe stress or social isolation is not healthy).

The distinction is important. Being disease-free is necessary for being healthy, but it is not sufficient. Health encompasses a more holistic state of well-being.

Health is influenced by:

Genetic disorders: Defects inherited from parents.
Infections: Caused by pathogens.
Lifestyle: Habits like food intake, water, rest, exercise, patterns of behaviour.

Good health can be achieved and maintained by:

Balanced diet.
Personal hygiene.
Regular exercise.
Awareness about diseases and their effect on the body.
Vaccination against infectious diseases.
Proper disposal of waste.
Control of vectors.
Maintenance of hygienic food and water resources.

Disease And Its Causes

When a person is not healthy, they are said to be suffering from a disease. Disease literally means 'disturbed ease' or 'discomfort'. A disease can cause damage to the body and affect its functions.

What Does Disease Look Like?

The presence of a disease is indicated by symptoms and signs.

Symptoms: Subjective feelings experienced by the patient (e.g., headache, nausea, pain). They are not directly observable by others.
Signs: Objective indicators of disease that can be observed or measured by others (e.g., fever, rash, high blood pressure, presence of bacteria in a lab test).

Symptoms and signs help doctors diagnose a disease. Different diseases have different sets of symptoms and signs.

Acute And Chronic Diseases

Diseases can be classified based on their duration:

Acute Diseases: Diseases that last for a short period of time. Symptoms are usually severe and appear suddenly.
Example: Common cold, Typhoid, Cholera.
Chronic Diseases: Diseases that last for a long period of time, sometimes even a lifetime. Symptoms are often less severe initially but can worsen over time and cause long-term damage.
Example: Tuberculosis (TB), Diabetes, Arthritis, Cancer.

Chronic Diseases And Poor Health

Chronic diseases have a more profound and lasting impact on a person's health compared to acute diseases.

They can cause significant long-term damage to organs and tissues.
They lead to prolonged poor health, affecting the individual's physical, mental, and social well-being.
They can cause permanent disability or significantly reduce the quality of life.
They can require long-term medical care and management.
Infectious diseases like TB can significantly reduce weight and cause persistent fatigue. Even non-infectious diseases like diabetes can have long-term effects on various organ systems.

Causes Of Diseases

Diseases can be caused by various factors. Understanding the cause is important for prevention and treatment.

Immediate cause: The direct factor that triggers the disease (e.g., a specific virus causing influenza, a specific bacterium causing TB).
Contributory causes: Factors that make a person more susceptible to the disease or influence its severity (e.g., poor nutrition, lack of clean water, poverty, genetic predisposition, weak immune system).

Infectious And Non-infectious Causes

Based on the immediate cause, diseases are classified as:

Infectious Diseases: Caused by pathogens (disease-causing microorganisms) that can spread from an infected person to others.
Examples: Bacteria, viruses, fungi, protozoa, worms. Examples of diseases: Common cold, Influenza, TB, Malaria, AIDS, COVID-19.

Infectious diseases lead to a vast majority of acute diseases.
Non-infectious Diseases: Diseases that are not caused by pathogens and do not spread from person to person.
Examples: Genetic disorders, deficiency diseases (lack of nutrients), lifestyle diseases (e.g., diabetes, heart disease, cancer, obesity), injuries.

Non-infectious diseases are usually the cause of chronic diseases, although some infectious diseases can also be chronic (e.g., TB, Hepatitis B, HIV infection).

Identifying whether a disease is infectious or non-infectious is the first step in determining the appropriate course of action for prevention and treatment.

Infectious Diseases

Infectious diseases are caused by pathogens (disease-causing microbes or organisms) that invade the body and can spread from one individual to another. They are a major cause of illness and mortality globally.

Infectious Agents

Pathogens are the organisms that cause infectious diseases. Different types of pathogens cause different diseases:

Bacteria: Cause diseases like Typhoid, Cholera, Tuberculosis (TB), Anthrax, Tetanus.
Viruses: Cause diseases like Common cold, Influenza, AIDS, Dengue, Chickenpox, Measles, Polio, COVID-19.
Fungi: Cause skin infections like ringworm, athlete's foot.
Protozoa: Cause diseases like Malaria (Plasmodium), Amoebiasis (Entamoeba histolytica), Kala-azar (Leishmania).
Worms (Helminths): Cause diseases like Ascariasis (Roundworm - Ascaris), Filariasis (Elephantiasis - Filarial worms).

The specific pathogen causing a disease determines the symptoms and the course of the illness.

Means Of Spread

Infectious diseases can spread through various means:

Airborne transmission: Through small droplets or aerosols containing pathogens, released when an infected person coughs, sneezes, talks, or sings.
Example: Common cold, Influenza, TB, COVID-19.
Waterborne transmission: Through contaminated water containing pathogens (often faecal contamination).
Example: Cholera, Typhoid, Amoebiasis, Hepatitis A.
Foodborne transmission: Through contaminated food.
Example: Food poisoning, Typhoid, Hepatitis A.
Vector-borne transmission: Through animals (vectors) that transmit pathogens from one person to another without getting infected themselves.
Example: Mosquitoes (transmit malaria, dengue, chikungunya), flies (transmit typhoid, cholera), fleas, ticks.
Sexual transmission: Through sexual contact (vaginal, anal, oral sex).
Example: Syphilis, Gonorrhoea, Genital herpes, HIV (causes AIDS).
Direct contact: Through physical contact with an infected person or their body fluids (e.g., skin infections, touching sores).
Indirect contact: Touching contaminated objects or surfaces (fomites).
Animal bites: Transmitting rabies virus (dog bite).
Vertical transmission: From infected mother to foetus during pregnancy or childbirth (e.g., HIV, Syphilis, Hepatitis B).

Organ-specific And Tissue-specific Manifestations

When pathogens enter the body, they often target specific organs or tissues where they cause disease. This is influenced by the entry point and the pathogen's affinity for certain tissues.

If bacteria enter through the mouth and reach the gut lining, they may cause typhoid (targeting the intestine).
If viruses enter through the nose and reach the lungs, they may cause pneumonia (targeting the lung tissue).
Malaria parasite (Plasmodium) enters the blood and targets liver cells and red blood cells.
HIV virus enters the body and primarily targets immune system cells (T-lymphocytes).

The symptoms of an infectious disease often depend on the organ or tissue that is targeted by the pathogen. For example, symptoms of TB vary depending on whether it affects the lungs, bones, or lymph nodes.

Principles Of Treatment

The treatment of infectious diseases depends on the type of pathogen causing the infection. Two main principles of treatment are:

Reducing the effects of the disease: Providing symptomatic relief to make the patient feel better (e.g., taking medicine to reduce fever, pain, or vomiting). This helps manage symptoms but does not kill the pathogen.
Killing the infectious agent: Using specific medications that target and kill the pathogen without significantly harming the host cells.
- Antibiotics: Medications that primarily target bacteria. They often work by disrupting bacterial cell wall synthesis or inhibiting bacterial metabolic pathways. Antibiotics are effective only against bacterial infections, not viral infections.
- Antiviral drugs: Medications that target viruses. Developing effective antiviral drugs is more challenging because viruses reproduce inside host cells, making it difficult to target the virus without harming host cells. Antiviral drugs often interfere with viral replication processes.
- Antifungal, antiprotozoal, anthelmintic drugs: Medications that target fungi, protozoa, and worms, respectively.

For many viral diseases (like common cold, influenza), there is no specific cure, and treatment focuses on relieving symptoms while the immune system fights the infection.

Principles Of Prevention

Prevention of infectious diseases is generally easier and more effective than treatment. Two main principles of prevention are:

General ways of preventing infections:
- Avoiding exposure to infectious agents: This includes maintaining personal hygiene (washing hands, covering mouth when coughing/sneezing), community hygiene (proper waste disposal, sanitation), providing safe drinking water, ensuring hygienic food preparation, controlling vectors (e.g., mosquito control to prevent malaria/dengue).
- Strengthening the immune system: By having a balanced diet, regular exercise, and sufficient rest.
Specific ways of preventing infections:
- Immunisation (Vaccination): Introducing a vaccine (weakened or killed pathogens, or parts of pathogens, or inactivated toxins) into the body. The vaccine stimulates the immune system to produce antibodies against the specific pathogen, providing immunity. If the body is later exposed to the actual pathogen, the immune system can rapidly mount a response and prevent the disease.
- Vaccination is available for many infectious diseases like polio, tetanus, diphtheria, measles, mumps, rubella, Hepatitis B, TB, COVID-19.

Public health measures focusing on hygiene, sanitation, clean water, and widespread vaccination programmes are essential for controlling the spread of infectious diseases in the community.

Common Diseases In Humans

Several infectious and non-infectious diseases are common in human populations. Here, we will focus on some common infectious diseases and their causes, symptoms, and transmission.

1. Typhoid:

Cause: Bacterium Salmonella typhi.

Transmission: Through contaminated food and water (faecal-oral route).

Symptoms: High fever ($39^\circ C \text{ to } 40^\circ C$), weakness, stomach pain, constipation, headache, loss of appetite. In severe cases, intestinal perforation and death can occur.

Diagnosis: Widal test.

Prevention: Maintaining hygiene, consuming clean food and water, vaccination.

2. Pneumonia:

Cause: Bacteria like Streptococcus pneumoniae and Haemophilus influenzae. Also caused by viruses and fungi.

Transmission: Through inhaling droplets/aerosols released by an infected person, or by sharing contaminated objects.

Target organ: Lungs. Alveoli fill with fluid, making breathing difficult.

Symptoms: Fever, chills, cough, headache. In severe cases, lips and fingernails may turn greyish to bluish.

Prevention: Avoiding contact with infected persons, maintaining hygiene, vaccination (for certain types).

3. Common Cold:

Cause: Various viruses, most commonly Rhinoviruses.

Transmission: Through inhaling droplets/aerosols from infected persons, or by touching contaminated objects and then touching face/nose/mouth.

Target organ: Nose and respiratory passage (but not lungs).

Symptoms: Nasal congestion and discharge, sore throat, cough, headache, tiredness. Usually lasts for 3-7 days.

Prevention: Avoiding contact, maintaining hygiene, washing hands frequently.

4. Malaria:

Cause: Protozoan parasite Plasmodium species (e.g., P. vivax, P. falciparum).

Transmission: By the bite of infected female Anopheles mosquito (vector).

Life cycle of Plasmodium involves two hosts: human and mosquito. The parasite multiplies in the liver cells, then invades Red Blood Cells (RBCs), where it multiplies, causing RBC rupture (leading to cycles of fever and chills). The release of haemozoin toxin from ruptured RBCs causes chills and high fever.

Symptoms: Recurring cycles of high fever with chills, headache, sweating.

Prevention: Mosquito control (reducing breeding sites, using mosquito nets and repellents), prompt diagnosis and treatment of infected individuals, using prophylactic drugs when travelling to malaria-prone areas.

(Image shows the life cycle of Plasmodium illustrating stages in human liver, RBCs, and mosquito gut/salivary glands)

5. Amoebiasis (Amoebic Dysentery):

Cause: Protozoan parasite Entamoeba histolytica.

Transmission: Through contaminated food and water containing cysts of the parasite (faecal-oral route). Houseflies are mechanical carriers.

Target organ: Large intestine.

Symptoms: Constipation, abdominal pain and cramps, stools with excess mucus and blood clots.

Prevention: Maintaining hygiene, consuming clean food and water, preventing faecal contamination.

6. Ascariasis:

Cause: Intestinal roundworm Ascaris lumbricoides.

Transmission: Through contaminated food and water containing eggs of the worm (faecal-oral route).

Target organ: Intestine. Worms live in the intestine.

Symptoms: Internal bleeding, muscular pain, fever, anaemia, blockage of the intestinal passage.

Prevention: Maintaining hygiene, consuming clean food and water, proper disposal of faeces.

7. Filariasis (Elephantiasis):

Cause: Filarial worms (e.g., Wuchereria bancrofti, W. malayi).

Transmission: By the bite of infected female mosquitoes (vector, typically Culex).

Target organ: Lymphatic vessels of the lower limbs and genital organs.

Symptoms: Chronic inflammation causing massive swelling and deformity, typically of the lower limbs and scrotum (giving the name elephantiasis). Develops gradually over many years.

Prevention: Vector control (mosquito eradication), using mosquito nets/repellents, timely treatment.

8. Ringworm:

Cause: Fungi, belonging to genera like Microsporum, Trichophyton, Epidermophyton.

Transmission: Through direct contact with infected person or contaminated objects (towels, clothes).

Target organ: Skin, nails, scalp.

Symptoms: Appearance of dry, scaly lesions on various parts of the body, intense itching. Heat and moisture help fungi grow.

Prevention: Maintaining personal hygiene, avoiding sharing personal items, keeping affected areas dry.

This is not an exhaustive list, but covers some of the common infectious diseases affecting humans.

Immunity

Immunity is the ability of the body to defend itself against disease-causing organisms (pathogens) and other foreign substances. The immune system is responsible for providing immunity.

Innate Immunity

Innate immunity is non-specific type of defence, present from the time of birth. It is the first line of defence against pathogens.
It involves various barriers that prevent the entry or multiplication of pathogens.
Innate immunity consists of four types of barriers:
- Physical barriers: Skin (prevents entry of microbes), mucous membrane lining the respiratory, gastrointestinal, and urogenital tracts (traps microbes).
- Physiological barriers: Acid in the stomach (kills bacteria), saliva in the mouth, tears from eyes (contain lysozyme, which kills bacteria).
- Cellular barriers: Certain types of leucocytes (WBCs) in the blood (e.g., phagocytic cells like neutrophils, monocytes/macrophages) that engulf and destroy microbes. Natural killer (NK) cells kill infected cells.
- Cytokine barriers: Viruses-infected cells secrete proteins called interferons. Interferons protect non-infected cells from further viral infection.

Acquired Immunity

Acquired immunity is pathogen-specific and is acquired after birth when the body is exposed to a pathogen or antigen. It involves the immune system 'learning' to recognise and respond to specific pathogens.
A primary response occurs upon the first exposure to a pathogen, which is relatively slow and produces a low-intensity immune response.
Subsequent exposures to the same pathogen elicit a highly intensified secondary or anamnestic response, which is faster and stronger. This is due to the presence of 'memory' cells.
Acquired immunity is mediated by two types of lymphocytes:
- B-lymphocytes (B cells): Produce antibodies (proteins that bind to specific antigens). Antibody-mediated immunity is called Humoral immunity.
- T-lymphocytes (T cells): Involved in cell-mediated immunity (CMI). T cells directly kill infected cells or help regulate other immune cells.

Diagram showing primary and secondary immune responses (antibody production over time)

*(Image shows a graph with antibody concentration on Y-axis and time on X-axis, illustrating a smaller, slower primary response upon first antigen exposure and a larger, faster secondary response upon subsequent exposure)*

Antibodies:

Antibodies are protein molecules called immunoglobulins (Ig).

They are produced by B-lymphocytes in response to specific antigens.

An antibody molecule has a Y-shape and is composed of four polypeptide chains: two light (L) chains and two heavy (H) chains. They are linked by disulfide bonds. ($H_2L_2$).

Different types of antibodies are produced in humans (IgA, IgM, IgG, IgE, IgD).

(Image shows a diagram of an antibody molecule highlighting the two heavy chains, two light chains, variable and constant regions, and disulfide bonds)

Active And Passive Immunity

Acquired immunity can be categorised as active or passive, depending on how the body gains immunity.

Active Immunity: Immunity developed when the body's own immune system produces antibodies in response to an antigen. It is slow but long-lasting.
- Natural active immunity: Developed after natural exposure to a pathogen (e.g., getting infected with chickenpox and becoming immune to future infection).
- Artificial active immunity: Developed after vaccination (introducing a vaccine containing antigens, stimulating the immune system to produce antibodies).
Passive Immunity: Immunity acquired when antibodies are transferred from outside into the body. The recipient's immune system does not produce the antibodies itself. It is fast-acting but short-lived.
- Natural passive immunity: Transfer of antibodies from mother to foetus through the placenta (IgG) or to the infant through colostrum (IgA).
- Artificial passive immunity: Administering pre-formed antibodies (e.g., in antiserum) to quickly provide protection against a specific pathogen or toxin (e.g., against tetanus, snake venom).

Vaccination And Immunisation

Vaccination is the process of administering a vaccine to stimulate an individual's immune system to develop immunity against a specific disease. Immunisation is the process by which the body develops immunity, either naturally or through vaccination.

Vaccines contain antigens (weakened or killed pathogens, parts of pathogens, or inactivated toxins).
When a vaccine is introduced, the body's immune system recognises the antigens and produces antibodies and memory cells.
If the person is later exposed to the actual pathogen, the memory cells quickly mount a strong secondary immune response, preventing the disease.
Vaccination is a highly effective strategy for preventing many infectious diseases and has led to the eradication or significant reduction of diseases like smallpox, polio, and measles.

Allergies

Allergy is an exaggerated response of the immune system to certain substances present in the environment. These substances are called allergens.
Examples of allergens: Pollen, dust mites, animal dander, certain foods, drugs.
Symptoms: Sneezing, watery eyes, running nose, difficulty breathing, skin rashes (hives).
Allergic reactions involve the production of antibodies (primarily IgE) and the release of chemicals like histamine and serotonin from mast cells, which cause inflammation and other symptoms.
Allergy diagnosis involves identifying the allergen (e.g., through skin tests). Treatment includes antihistamines, adrenaline, or steroids.

Auto Immunity

The immune system has the ability to distinguish between 'self' and 'non-self' cells and molecules.
Autoimmunity is a condition where the immune system mistakenly attacks the body's own cells and tissues, treating them as foreign.
This can lead to various autoimmune diseases, affecting specific organs or multiple systems.
The cause of autoimmune diseases is not fully understood, but genetic factors and environmental triggers are believed to play a role.
Example: Rheumatoid arthritis (immune system attacks joints), Type 1 diabetes (immune system attacks pancreatic beta cells), Multiple sclerosis (immune system attacks nerve myelin sheath).

Immune System In The Body

The human immune system is a complex network of organs, tissues, cells, and molecules. It includes:

Lymphoid organs: Sites where lymphocytes are produced, mature, and proliferate.
- Primary lymphoid organs: Bone marrow (production of all blood cells, maturation of B cells), Thymus (maturation of T cells).
- Secondary lymphoid organs: Spleen (filters blood, site of immune response), Lymph nodes (filter lymph, site of immune response), Tonsils, Peyer's patches (in small intestine), Appendix. These organs provide sites for interaction between lymphocytes and antigens.
Immune cells: Lymphocytes (B cells, T cells, NK cells), Phagocytic cells (macrophages, neutrophils), Antigen-presenting cells (dendritic cells).
Antibodies and other molecules: Cytokines, complement proteins.

The immune system surveils the body, detects foreign invaders and abnormal cells (like cancer cells), and mounts an immune response to eliminate them, providing a vital defence mechanism.

Diagram showing the major lymphoid organs in the human body

*(Image shows a diagram of the human body highlighting the locations of bone marrow, thymus, spleen, lymph nodes, tonsils, Peyer's patches, appendix)*

Aids

AIDS (Acquired Immunodeficiency Syndrome) is a chronic, potentially life-threatening condition caused by the Human Immunodeficiency Virus (HIV). It is characterised by a severe weakening of the immune system, making the body susceptible to opportunistic infections and certain cancers.

Cause:

Caused by HIV, a retrovirus. Retroviruses have RNA as their genetic material and use the enzyme reverse transcriptase to convert RNA into DNA after entering the host cell. This viral DNA then integrates into the host cell's DNA.

HIV primarily infects and destroys helper T-lymphocytes (also called CD4+ T cells), which are critical components of the immune system. The number of helper T cells declines significantly over time.

As helper T cells are destroyed, the immune system becomes severely compromised, losing its ability to fight off infections and certain cancers. AIDS is the final, most severe stage of HIV infection.

Transmission:

HIV is primarily transmitted through:

Sexual contact: Vaginal, anal, or oral sex with an infected person.

Contaminated blood and blood products: Transfusion of infected blood or blood products (though greatly reduced due to screening).

Sharing contaminated needles and syringes: Common among intravenous drug users.

From infected mother to child: During pregnancy, childbirth, or breastfeeding (vertical transmission).

HIV is NOT spread by casual contact (e.g., shaking hands, hugging, sharing food/utensils, using public toilets, mosquito bites).

Symptoms And Diagnosis:

Initial symptoms after infection may be mild and flu-like (acute retroviral syndrome).

After the initial phase, the infection enters a latent stage, which can last for years, with few or no symptoms. The virus continues to multiply during this time.

As the immune system weakens, symptoms become more severe, including persistent fever, chronic diarrhoea, weight loss, swollen lymph nodes.

AIDS is diagnosed when the CD4+ T cell count drops below a critical level and/or the person develops certain opportunistic infections (e.g., Pneumocystis pneumonia, toxoplasmosis, candidiasis) or cancers (e.g., Kaposi's sarcoma).

Diagnosis of HIV infection is done by tests that detect HIV antibodies (e.g., ELISA - Enzyme-Linked Immunosorbent Assay) or viral RNA/DNA. A positive ELISA test needs to be confirmed by a Western blot test or other confirmatory tests.

Complications:

Opportunistic infections (TB, pneumonia, candidiasis, toxoplasmosis).

Certain cancers.

Neurological complications.

Wasting syndrome (severe weight loss).

Prevention:
Prevention is key as there is no cure for HIV infection or AIDS, though treatment can manage the virus and prolong life.

Educating people about HIV transmission and prevention.

Promoting safe sexual practices (using condoms consistently and correctly, reducing number of sexual partners).

Avoiding sharing needles and syringes.

Ensuring safe blood transfusions (screening blood for HIV).

Using sterile needles and equipment for injections, tattooing, piercing.

Preventing vertical transmission from mother to child (using antiretroviral therapy during pregnancy and childbirth, avoiding breastfeeding).

Offering voluntary counselling and testing (VCT).

There is no vaccine for HIV infection yet. Antiretroviral Therapy (ART) is available, which can suppress the virus, improve immune function, reduce the risk of transmission, and allow people with HIV to live longer, healthier lives. However, ART is a lifelong treatment.

Cancer

Cancer is a disease characterised by the uncontrolled and abnormal growth of cells. These cells divide continuously and invade other tissues, forming tumours.

Cancer is a major cause of death worldwide. Unlike normal cells which have controlled cell division and undergo apoptosis (programmed cell death), cancer cells lose these regulatory mechanisms.

Tumours can be:

Benign tumours: Non-cancerous. They are usually confined to their original location and do not spread to other parts of the body. They are generally less harmful but can cause problems if they compress vital structures.
Malignant tumours: Cancerous. These cells proliferate rapidly, invade surrounding normal tissues, and can spread to distant sites through blood or lymph, forming secondary tumours called metastases. Metastasis is the most feared property of malignant tumours.

Causes Of Cancer

The transformation of normal cells into cancerous cells can be caused by physical, chemical, or biological agents called carcinogens.

Chemical carcinogens: Substances like tobacco smoke (causes lung, bladder, oral cancer), certain chemicals in industrial pollutants, dyes, pesticides.
Physical carcinogens: Ionising radiations (X-rays, gamma rays) and non-ionising radiations (UV radiation) can cause DNA damage leading to mutations, increasing cancer risk.
Biological agents (Oncogenic viruses): Certain viruses contain genes called viral oncogenes that can cause cancer (e.g., Human Papillomavirus - HPV linked to cervical cancer, Hepatitis B and C viruses linked to liver cancer).
Oncogenes (Cellular oncogenes or proto-oncogenes): Normal cells have genes called proto-oncogenes that control cell growth and division. Mutations in these genes or their abnormal activation can convert them into oncogenes, leading to uncontrolled cell proliferation.
Tumour suppressor genes: Genes in normal cells that inhibit cell division and promote apoptosis. Mutations in these genes can lead to loss of their inhibitory function, contributing to cancer development.

Cancer is often a multi-step process involving the accumulation of multiple mutations over time.

Cancer Detection And Diagnosis

Early detection is crucial for successful cancer treatment.

Biopsy and histopathological studies: A piece of suspected tissue is taken and examined under a microscope by a pathologist to identify cancerous cells. This is the most definitive method.
Radiography (X-rays): Used to detect tumours in internal organs (e.g., chest X-ray for lung cancer).
CT scan (Computed Tomography): Uses X-rays to create cross-sectional images of the body, providing detailed views of organs and tumours.
MRI (Magnetic Resonance Imaging): Uses magnetic fields and radio waves to create detailed images of tissues and organs. Useful for detecting cancers in soft tissues.
PET scan (Positron Emission Tomography): Uses a radioactive tracer to visualise metabolic activity in tissues. Cancer cells are often more metabolically active and show up as bright spots.
Endoscopy: Using a flexible tube with a camera to visualise the inside of organs (e.g., colonoscopy for colon cancer).
Blood and bone marrow tests: Used in blood cancers like leukaemia.
Detection of specific cancer antigens: Some cancers produce specific antigens (tumour markers) that can be detected in blood or other body fluids (e.g., PSA for prostate cancer, CEA for colorectal cancer).
Molecular biology techniques: Detecting gene mutations or chromosomal abnormalities associated with specific cancers.

Treatment Of Cancer

Treatment of cancer depends on the type of cancer, its stage, and the patient's overall health. Common treatment modalities include:

Surgery: Removal of the tumour. Effective for many localised cancers.
Radiotherapy (Radiation therapy): Using high-energy radiation to kill cancer cells. Targeted to the tumour site. Can damage surrounding healthy tissues.
Chemotherapy: Using anti-cancer drugs (cytotoxic drugs) that kill rapidly dividing cells, including cancer cells. Can cause side effects as they also affect rapidly dividing normal cells (e.g., hair follicles, bone marrow cells, lining of digestive tract).
Immunotherapy: Stimulating the patient's own immune system to recognise and kill cancer cells.
Targeted therapy: Using drugs that specifically target molecular pathways involved in cancer growth, often with fewer side effects than traditional chemotherapy.
Combination therapy: Often, a combination of these treatments is used for better results.

Cancer treatment aims to eradicate cancer cells, prevent recurrence, and improve the patient's quality of life. Early detection significantly improves the prognosis.

Drugs And Alcohol Abuse

Drug abuse refers to the non-medical use of certain drugs for recreational purposes, often leading to physical and psychological dependence. Alcohol abuse refers to excessive and harmful consumption of alcoholic beverages. Abuse of drugs and alcohol is a significant public health and social problem, particularly affecting young people.

Adolescence And Drug/Alcohol Abuse

Adolescence: The period of transition from childhood to adulthood (roughly 12-18 years of age). It is a vulnerable period characterised by significant physical, psychological, and social changes.
Curiosity, a desire for adventure and experimentation, peer pressure, a need for acceptance, stress from academic pressure or uncertain future, and sometimes family problems can push young people towards drug and alcohol abuse.
Initial use may be experimental, but can quickly lead to addiction and dependence.

Addiction And Dependence

Addiction: A psychological attachment to certain effects (e.g., euphoria, feeling of well-being) associated with drugs or alcohol. It drives the person to take them repeatedly.
Dependence: The body's physiological need for the drug or alcohol. When regular dose is abruptly discontinued, the body shows withdrawal symptoms (anxiety, shakiness, nausea, sweating). This painful experience leads the person to resume using the substance. Dependence develops over time with repeated use.

Effects Of Drug/Alcohol Abuse

Abuse of drugs and alcohol can have devastating effects on the individual, their family, and society.

Short-term effects: Impaired judgement, poor coordination, slurred speech, nausea, vomiting, anxiety, mood swings, increased risk-taking behaviour, accidents.
Long-term effects:
- Damage to vital organs: Liver damage (cirrhosis) and kidney damage (alcohol abuse), brain damage, heart problems.
- Mental health issues: Depression, anxiety disorders, psychosis, cognitive impairment.
- Weakened immune system: Increased susceptibility to infections.
- Nutritional deficiencies.
- Addiction and dependence.
- Social problems: Breakdown of family relationships, financial problems, unemployment, criminal activities.
- Increased risk of STIs and HIV/AIDS (due to sharing needles or risky sexual behaviour).
Specific drugs have specific effects (e.g., opioids cause drowsiness and slow breathing, stimulants increase alertness and heart rate).

Prevention And Control

Preventing and controlling drug and alcohol abuse requires a multi-pronged approach involving individuals, families, schools, and the community.

Education and Counselling: Educating young people about the risks and consequences of drug and alcohol abuse. Providing counselling to help them cope with stress and peer pressure.
Identifying Danger Signs: Recognising early signs of drug/alcohol abuse (e.g., changes in behaviour, academic performance, social circle, hygiene).
Seeking Help: Encouraging individuals struggling with abuse to seek professional medical and psychological help. Rehabilitation centres and counselling services are available.
Support from Family and Friends: Providing a supportive and understanding environment.
Avoiding Peer Pressure: Teaching young people skills to resist peer pressure.
Looking for Danger Signs in Youth: Parents and teachers should be vigilant about behavioural changes that may indicate drug/alcohol abuse.
Seeking Professional and Medical Help: Qualified psychologists, psychiatrists, and de-addiction centres can provide effective treatment and rehabilitation.
Awareness Programs: Organising campaigns to educate the public about the harms of drug and alcohol abuse.

Early intervention, support, and access to treatment are crucial for helping individuals overcome addiction and lead healthy lives. It is important to view addiction as a medical problem that requires treatment, rather than a moral failing.