18.1

Communicable Diseases

• A communicable disease is a disease that can be transmitted from one person to another through various means, such as direct contact, airborne transmission, or through vectors like mosquitoes.
• Examples of communicable diseases include malaria, influenza, and tuberculosis.

The Body's Defense Against Disease

• The body has multiple lines of defense against disease, including:
  • The first line of defense: the body's outer barriers, such as skin and mucous membranes, which prevent pathogens from entering the body.
  • The second line of defense: the immune system, which includes phagocytes, inflammation, and fever, which work to eliminate pathogens that have entered the body.
  • The third line of defense: the immune system's specific response to pathogens, which includes the production of antibodies and activation of T cells.

Pathogens

• There are four types of pathogens:
  • Bacteria: single-celled organisms that can cause diseases, such as E. coli and Staphylococcus aureus.
  • Viruses: tiny particles that require a host cell to replicate, and can cause diseases, such as the common cold and influenza.
  • Fungi: complex organisms that include mushrooms, molds, and yeast, which can cause diseases, such as pneumonia.
  • Parasites: organisms that live on or inside other organisms, such as protozoa and worms, which can cause diseases, such as malaria and dysentery.

Stages of Infection

• The stages of infection include:
  • Incubation period: the time between the pathogen's entry into the body and the first symptoms.
  • Symptoms: the physical manifestations of the disease, such as fever, cough, and fatigue.
  • Recovery: the body's response to the infection, which may include the production of antibodies and the activation of immune cells.

Methods of Transmission

• Diseases can be transmitted through various means, including:
  • Direct contact: touching, shaking hands, or sharing food and drinks with an infected person.
  • Airborne transmission: breathing in droplets or particles that contain pathogens.
  • Indirect transmission: touching contaminated surfaces or objects, or through vectors like mosquitoes.
  • Vector transmission: through the bite of an infected insect, such as a mosquito.

Immunity

• Immunity is the body's ability to defend itself against infectious microorganisms.
• There are two types of immunity:
  • Innate immunity: the body's first line of defense, which includes physical barriers and chemical defenses.
  • Adaptive immunity: the body's specific response to pathogens, which includes the production of antibodies and activation of T cells.

Vaccination

• Vaccination is a way to stimulate the adaptive immune system to produce antibodies against a specific pathogen.
• Vaccines can be used to prevent diseases, such as measles, influenza, and HPV.

Body Systems of the First Line of Defense

• The body's first line of defense includes:
  • Integumentary system: the skin and mucous membranes, which provide a physical barrier against pathogens.
  • Respiratory system: the lungs and airways, which filter out pathogens and produce mucus to trap them.
  • Digestive system: the stomach and intestines, which produce acid and enzymes to break down and destroy pathogens.
  • Urinary system: the kidneys and bladder, which produce urine to flush out pathogens.

Local and Global Health

• Communicable diseases are a major public health concern, particularly in low-income countries.
• Vaccines have been successful in preventing and controlling diseases, but there is still a need for increased access to vaccination programs, especially in low-income countries.
• Measles is a major concern, with 95% of measles deaths occurring in low-income countries.
• The number of measles cases in the US is growing, particularly in areas with low vaccination rates.