Understanding Disease, Immunity, and STIs: Core Concepts

Core Concepts of Health and Disease

Health and Disease Definitions

• Health: A state of complete physical, mental, and social well-being, and not merely the absence of disease or infirmity.
• Disease: A disorder or malfunction of the mind or body, which leads to a departure from good health. It can be a disorder of a specific tissue or organ due to a single cause.

Pathogens and Infectious Diseases

Types of Pathogens

• Fungi
• Bacteria
• Viruses

Diseases Caused by Viruses

Influenza (Flu)

Influenza is a virus that causes a severe form of respiratory tract infection with generalized bodily symptoms. While it shares cold-like symptoms, its onset is rapid and violent, often featuring:

• High fever
• Severe aches and pains, often in the back and muscles

Other common viral diseases include:

• Measles
• Chickenpox

Diseases Caused by Bacteria

Tuberculosis (TB)

Tuberculosis (TB) is a bacterial infection spread through inhaling tiny droplets from the coughs or sneezes of an infected person. It mainly affects the lungs, but it can affect any part of the body, including the bones and nervous system.

Typical Symptoms of Tuberculosis

• A persistent cough for more than three weeks that brings up phlegm, which may be bloody.
• Weight loss.
• Fever.

Disease Caused by Parasites: Malaria

Malaria is spread by mosquitoes, blood transfusions, and shared hypodermic needles. Infected individuals can be treated with a variety of medicines. However, some of the sporozoans that cause malaria have developed immunity to some of the more commonly employed medicines.

Non-Infectious Conditions

Degenerative Diseases

Examples of degenerative diseases include:

• Multiple Sclerosis
• Parkinson's Disease

Defenses Against Disease

First Line of Defense (Physical Barriers)

• Saliva
• Tears
• Skin
• Mucus
• Stomach Acid

Second Line of Defense (Non-Specific Immunity)

Invading pathogens are targeted by macrophages (phagocytic cells).

Specific Immune Response (Adaptive Immunity)

This response involves targeted action against specific threats:

1. Lymphocytes detect the presence of foreign antigens.
2. They are stimulated to produce specific proteins called antibodies.
3. Antibodies combine with their specific antigen.
4. This renders the pathogen harmless.

Sexually Transmitted Infections (STIs)

Definitions

• STD (Sexually Transmitted Disease): A disease transmitted through sexual contact.
• STI (Sexually Transmitted Infection): An infection transmitted through sexual contact (may be asymptomatic or "silent").

Types of STIs

Bacterial STIs (Treated with Antibiotics)

• Chlamydia
• Gonorrhea
• Syphilis

Viral STIs (Managed with Medication)

• Herpes Genitalis
• Human Papillomavirus (HPV)
• Human Immunodeficiency Virus (HIV)

Focus on Chlamydia

Chlamydia often presents as a urinary tract infection in both males and females. Symptoms may include a yellowish vaginal discharge, and infected tissues may become red and irritated. Importantly, some cases may be asymptomatic. It is typically treated with antibiotics.

Acquired Immune Deficiency Syndrome (AIDS)

AIDS is a condition that is caught, not inherited. It is caused by the Human Immunodeficiency Virus (HIV).

Mechanism and Consequences of HIV/AIDS

The virus attacks the immune system, specifically living and reproducing in helper T cells (a type of white blood cell). The consequence is a decrease in helper T cells, which are necessary for stimulating antibody production by B cells and the activity of killer T cells. This immune suppression leads to opportunistic infections and cancers in infected persons.

HIV is transmitted when infected fluids enter the body, typically through sexual contact or contaminated needles.