18.1

Study Notes

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 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.

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.

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.

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 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 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.

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.

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.