Common Diseases In Humans

Health is defined as a state of complete physical, mental, and social well-being, not merely the absence of disease. It is influenced by genetic disorders, infections, and lifestyle factors like diet, hygiene, rest, and exercise. Diseases can be broadly classified into infectious and non-infectious.

Infectious Diseases are caused by pathogens (disease-causing organisms like bacteria, viruses, fungi, protozoans, and helminths) and are transmissible. Examples include:

• Typhoid Fever: Caused by Salmonella typhi bacteria, entering through contaminated food and water. Symptoms include sustained fever, weakness, abdominal pain, and constipation.
• Pneumonia: Caused by bacteria like Streptococcus pneumoniae and Haemophilus influenzae, infecting the lung alveoli, leading to fluid accumulation and breathing difficulties.
• Common Cold: Caused by rhinoviruses, affecting the nose and respiratory passages, characterized by nasal discharge, sore throat, and cough.
• Malaria: Caused by Plasmodium protozoa, transmitted by infected female Anopheles mosquitoes. The parasite infects liver cells and red blood cells, causing fever and chills due to the release of haemozoin.
• Amoebiasis (Amoebic Dysentery): Caused by Entamoeba histolytica, an intestinal parasite. Symptoms include abdominal pain, cramps, and bloody stools. Houseflies act as mechanical vectors.
• Ascariasis: Caused by the roundworm Ascaris, an intestinal parasite. Symptoms include muscular pain, fever, anemia, and intestinal blockage. Infection occurs through contaminated food and water.
• Filariasis (Elephantiasis): Caused by Wuchereria (filarial worms), which infect lymphatic vessels, leading to chronic inflammation and gross deformities, typically in the lower limbs. Transmitted by female mosquitoes.
• Ringworm: Caused by fungi (e.g., Microsporum, Trichophyton) in skin folds, characterized by dry, scaly lesions and intense itching. Acquired through contact with infected individuals or contaminated items.

Prevention and control involve personal hygiene (cleanliness, safe food/water), public hygiene (waste disposal, clean water sources), avoiding contact with infected individuals and their belongings (for airborne diseases), and controlling vectors (like mosquitoes) by eliminating breeding sites and using protective measures like nets and insecticides.

Immunity

Immunity is the body's ability to defend itself against disease-causing organisms (pathogens), conferred by the immune system. It is of two types:

Innate Immunity

Innate immunity is non-specific and present from birth. It provides general defense through various barriers:

• Physical Barriers: Skin and mucous membranes lining the respiratory, gastrointestinal, and urogenital tracts trap microbes.
• Physiological Barriers: Acid in the stomach, saliva in the mouth, and tears from the eyes inhibit microbial growth.
• Cellular Barriers: Phagocytic cells like neutrophils, monocytes, macrophages, and natural killer (NK) lymphocytes engulf and destroy microbes.
• Cytokine Barriers: Virus-infected cells release proteins called interferons, which protect adjacent non-infected cells from viral infection.

Acquired Immunity

Acquired immunity is pathogen-specific and characterized by immunological memory. Upon first exposure (primary response), the immune system produces a low-intensity response. Subsequent encounters elicit a faster, stronger response (secondary/anamnestic response) due to this memory. It involves two types of lymphocytes:

• B-lymphocytes: Produce antibodies, which are proteins that combat pathogens. This is known as humoral immunity.
• T-lymphocytes: Mediate cell-mediated immunity (CMI), directly attacking infected cells or helping B-cells.

The body's ability to differentiate 'self' from 'non-self' is crucial for immune function and graft rejection.

Active And Passive Immunity

• Active Immunity: Developed when the host encounters antigens (pathogens or their components), triggering antibody production by the host's immune system. It is slow but provides long-lasting protection. Natural infection or vaccination induces active immunity.
• Passive Immunity: Administered by introducing pre-formed antibodies (e.g., antitoxins, colostrum from the mother containing IgA, or antibodies transferred across the placenta). It provides immediate but short-term protection.

Vaccination And Immunisation

Vaccination relies on the immune system's memory. Vaccines (containing weakened or inactivated pathogens, or antigenic proteins) are introduced into the body, stimulating a primary immune response and generating memory B and T-cells. This prepares the body for a rapid and robust response upon subsequent exposure to the actual pathogen. In cases like tetanus or snakebites, pre-formed antibodies (antitoxins) are directly administered (passive immunization).

Allergies

Allergies are exaggerated immune responses to certain environmental antigens called allergens (e.g., dust pollen, mites, animal dander). These responses involve the release of chemicals like histamine and serotonin from mast cells, causing symptoms like sneezing, watery eyes, and breathing difficulties. IgE antibodies are primarily involved. Modern lifestyles may contribute to increased sensitivity and allergies.

Auto Immunity

Autoimmune diseases occur when the immune system mistakenly attacks the body's own cells ('self'). This is due to a failure in the 'self' vs. 'non-self' recognition mechanism. Rheumatoid arthritis is an example of an autoimmune disease.

Immune System In The Body

The immune system comprises lymphoid organs, tissues, cells (lymphocytes), and molecules (antibodies). Lymphoid organs are sites of lymphocyte origin, maturation, and proliferation.

• Primary Lymphoid Organs: Bone marrow (where lymphocytes originate and B-cells mature) and thymus (where T-cells mature).
• Secondary Lymphoid Organs: Spleen, lymph nodes, tonsils, Peyer's patches (in the small intestine), and appendix. These are sites where lymphocytes interact with antigens to initiate an immune response.
• Mucosa-Associated Lymphoid Tissue (MALT): Lymphoid tissue found in the lining of major tracts, constituting about 50% of the body's lymphoid tissue.

Aids

AIDS (Acquired Immuno Deficiency Syndrome) is caused by the Human Immuno deficiency Virus (HIV), a retrovirus. HIV primarily targets and destroys helper T-lymphocytes (TH cells), crucial components of the immune system. This leads to a progressive decline in cell-mediated and humoral immunity, making the individual susceptible to opportunistic infections (caused by bacteria, viruses, fungi, and parasites) and certain cancers.

Transmission: HIV is transmitted through sexual contact with an infected person, transfusion of contaminated blood or blood products, sharing infected needles (common among intravenous drug users), and from an infected mother to her child through the placenta.

Symptoms and Progression: There is often a long incubation period (5-10 years or more) between infection and the manifestation of AIDS symptoms. Initially, the virus replicates in macrophages and then infects helper T-cells. A progressive decrease in the number of T-cells severely weakens the immune system. Patients may suffer from fever, diarrhea, weight loss, and eventually succumb to infections that a healthy immune system could easily overcome.

Diagnosis and Treatment: ELISA (Enzyme-Linked Immuno-Sorbent Assay) is a common diagnostic test. While anti-retroviral drugs can prolong life, there is no known cure for AIDS.

Prevention: Prevention is the best strategy. This includes safe sex practices, avoiding multiple sexual partners, using sterile needles and syringes, ensuring safe blood transfusions, controlling drug abuse, and educating the public about transmission and prevention. Early detection and support for infected individuals are crucial.

Cancer

Cancer is a group of diseases characterized by uncontrolled cell growth and proliferation, leading to the formation of tumors. This occurs due to a breakdown in the regulatory mechanisms controlling cell division and differentiation. Normal cells exhibit 'contact inhibition,' halting growth upon contact with other cells, a property lost by cancer cells.

Types of Tumors:

• Benign Tumors: Remain localized, do not spread to other parts, and cause minimal damage.
• Malignant Tumors: Characterized by rapid proliferation, invasion of surrounding tissues, and metastasis – the spread of cancerous cells through blood or lymph to distant sites, forming secondary tumors. This metastatic potential is the most feared aspect of cancer.

Causes (Carcinogens): Cancer can be induced by physical agents (ionizing radiation like X-rays, gamma rays), chemical agents (e.g., tobacco smoke components), and biological agents (oncogenic viruses carrying viral oncogenes). Cellular oncogenes (proto-oncogenes) present in normal cells can also become activated, leading to cancer.

Detection and Diagnosis: Early detection is vital for successful treatment. Methods include biopsy and histopathological examination of tissues, blood tests (for increased cell counts in leukemia), radiography, CT scans, and MRI to visualize internal tumors. Cancer-specific antigens can be detected using antibodies, and molecular biology techniques can identify genes predisposing individuals to certain cancers.

Treatment: Common treatment modalities include surgery, radiation therapy (using lethal doses of radiation to kill tumor cells while sparing surrounding tissues), and immunotherapy (using biological response modifiers like alpha-interferon to boost the immune system's ability to fight cancer).

Drugs And Alcohol Abuse

Substance abuse, particularly among youth, is a significant public health concern due to its detrimental effects on physical, mental, and social well-being. The commonly abused substances include opioids, cannabinoids, and coca alkaloids, often derived from flowering plants or fungi.

Adolescence And Drug/Alcohol Abuse

Adolescence (ages 12-18) is a vulnerable period marked by biological and psychological changes. Curiosity, a desire for adventure, experimentation, peer pressure, stress (academic, social), and perceived 'coolness' associated with substance use are common motivators for adolescents to experiment with drugs and alcohol. Media portrayal also plays a role in shaping these perceptions.

Addiction And Dependence

Repeated drug use can lead to addiction, a psychological dependence characterized by a craving for the substance's effects (e.g., euphoria), even when detrimental. Tolerance develops, requiring higher doses for the same effect. Dependence is a physiological state where the body exhibits unpleasant withdrawal symptoms (anxiety, nausea, tremors) upon abrupt cessation of the substance, which are often relieved by resuming use. This can lead to self-destructive behavior and disregard for social norms.

Effects Of Drug/Alcohol Abuse

Immediate adverse effects include reckless behavior, violence, and impaired judgment. Overdosing can lead to coma and death from respiratory or cardiac failure. Chronic use damages the nervous system and liver (cirrhosis). Intravenous drug users are at high risk for HIV and Hepatitis B infections due to needle sharing. Substance abuse during pregnancy can harm the fetus. Sportspersons may abuse anabolic steroids to enhance performance, leading to various side effects like mood swings, aggression, hormonal imbalances, and potential organ damage.

Warning signs among youth include decreased academic performance, social withdrawal, neglect of personal hygiene, aggression, and strained relationships.

Prevention And Control

Prevention is paramount. Key strategies include:

• Parental and Teacher Guidance: Providing nurturing and supportive environments, consistent discipline, and education about the risks of substance abuse.
• Education and Counseling: Helping adolescents cope with stress, face challenges, and understand the negative consequences of substance use. Channeling energy into healthy activities like sports, music, and yoga is beneficial.
• Peer Support: Encouraging open communication with parents and trusted friends for guidance and emotional support.
• Early Recognition of Danger Signs: Identifying warning signs of substance abuse and seeking timely professional help.
• Professional Help: Utilizing psychologists, psychiatrists, and rehabilitation programs for treatment and recovery.

Awareness campaigns and accessible support systems are crucial to combating drug and alcohol abuse.

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