Disease Types and Host Resistance

• Pathogens can cause diseases, ranging from mild colds to severe illnesses like AIDS.

Types of Disease

• Latent diseases: The causative agent remains inactive for a time, then becomes active (e.g., chickenpox leading to shingles).
• Communicable diseases: Spread easily through direct or indirect contact (e.g., herpes, malaria, influenza).
• Contagious diseases: Spread very easily through close exposure (e.g., chickenpox, whooping cough, HIV/AIDS).
• Infectious diseases: Need direct entry into the body and are not always contagious (e.g., malaria, ringworm).
• Carriers: People who have the germ and can pass it on without showing symptoms (e.g., typhoid fever).
• Contact: Refers to anyone who has been close to an infected person, animal, or contaminated material (e.g., family member with the flu).

State of Host Resistance

• Primary infection: The initial, acute infection that causes the first noticeable illness.
• Secondary infection: Occurs when an opportunistic pathogen infects after the primary infection weakens defenses.
• Subclinical infection: An infection that does not cause noticeable symptoms.

Classification of Infectious Diseases

• Sporadic diseases: Occur occasionally and irregularly, with no predictable pattern (e.g., tetanus).
• Endemic diseases: Constantly present in a specific population, country, or community (e.g., tuberculosis in the Philippines).
• Epidemic diseases: A sudden increase in cases, exceeding the normal expected number in an area (e.g., cholera outbreaks).
• Pandemic diseases: An epidemic that spreads across multiple countries or worldwide (e.g., COVID-19).

Severity/Duration of Disease

• Acute diseases: Develops rapidly and lasts for a short period (e.g., measles, mumps, influenza).
• Chronic diseases: Develops slowly with an insidious onset and tends to be long-lasting or recurrent (e.g., tuberculosis, leprosy).
• Subacute diseases: Falls between acute and chronic in onset and duration (e.g., bacterial endocarditis).

Stages of Disease

• Incubation period: Time between infection and first signs; feels completely normal.
• Prodromal period: Early, mild symptoms begin to show up.
• Period of illness: Active/sick period; symptoms are at their worst.
• Period of decline: Symptoms start to fade as the body controls the infection.
• Period of convalescence: Recovery phase; the infection is halted, and the patient regains strength.
• Acquired immunity: Equips the immune system to react quickly, potentially stopping the disease during the prodromal period.

Microbes Against Humans

• Symptoms: What a patient feels (subjective signs), like pain or fatigue.
• Signs: What a doctor can observe (objective evidence), such as a rash or fever.
• Syndrome: A collection of signs and symptoms that characterize a disease.
• Incidence: The number of new cases in a population during a specific time period.
• Prevalence: The total number of cases (new and existing) in a population at a particular time.

Infection

• Infection: Condition caused by the entry and multiplication of pathogenic microorganisms.
• Pathogenicity: The microbe's ability to cause disease.
• Infective dose: The minimum number of organisms needed to start an infection.
• Virulence & invasiveness: Indicates how severe the disease is and the microbe's ability to enter and move through tissues.
• Organism specificity: The preference of the microbe for a particular host.
• Host resistance & immunity: How well the host's defenses can prevent or fight the infection.

Chain of Infection

Reservoir

• Where germs live.
• Examples include people, animals, food, soil, and water.

Portal of Exit

• How germs get out
• Mouth (vomit, saliva), cuts in the skin (blood)

Mode of Transmission

• Contact (hands, toys, sand).
• Droplets (when speaking, sneezing, or coughing).

Portal of Entry

• How germs get in
• Mouth, cuts in the skin, eyes

Susceptible Host

• Next sick person
• e.g. babies, children, the elderly, people with weakened immune systems, and the unimmunized.

Infection control

• Hand hygiene: The first line of defense and the most important practice in preventing infection.

Immunity

• Immunity: The body's ability to resist and overcome diseases.
• Immune system: Protects using cells and substances like antibodies.
• Antibodies: Proteins produced by immune cells in response to antigens.
• Antigen: Any foreign substance that triggers an immune response.
• Vaccines: Introduce antigens to create immunity.

Types of vaccine

• Inactivated vaccines: Use killed organisms and usually require multiple doses or boosters.
• Attenuated vaccines: Use live but weakened organisms and typically need only one dose for long-lasting protection.

Immunization

• Active immunization: Stimulates the body to produce its own antibodies (e.g., routine and non-routine vaccines).
• Passive immunization: Provides pre-made antibodies directly (e.g., Diphtheria antitoxin, HBIG).

Vaccine storage and handling

• Check expiry date on the label, avoiding sunlight, storing vaccines at a temperature of 0-8°C, and water only for cleaning.

Expanded Program on Immunization (EPI)

• EPI Code: PPD 996; Goal: Universal child immunization

Expanded Program of Immunization

• EPI targets these diseases: TB, Measles, Diphtheria/Pertussis, Polio, Tetanus, Hepatitis

Immunoglobulin

• Most common (80%); produced later in immune response, is the only Ig that crosses the placenta to protect the fetus
• Found in colostrum, tears, saliva and sweat, and protects mucosal surfaces
• Main antibody in blood, is quickly produced in response to an antigen, and important in early defense and following vaccination
• Involved in allergic reactions and protection against parasites
• Functions as an antigen receptor on B cells; full role less clearly defined

Vaccine Contraindications

• Severe febrile illness and altered immune system

Epidemiology and Disease Transmission

• Reservoirs of infection: Sites where pathogens multiply or survive (e.g., human reservoir).
• Transmission: How the pathogen spreads (e.g., direct or indirect)

Precaution Guidelines

• Airborne, Droplet, and Contact precautions should be used in a hospital setting

Isolation Precautions Guide

• Contact, Strict, Respiratory, & TB should be followed in a hospital setting

Isolation and Disposal Precautions

• Precautions around secretion, environmental controls, invasive procedures, excretion, and blood.

Waste management and color coding for healthcare facilities in the Philippines

• Sharps are yellow, non-infectious waste is black and biodegradeable is green

Means of Controlling Communicable Diseases

• Eliminating the source of infection.
• Interrupting transmission with hygiene, isolation, and PPE use.
• Protecting susceptible hosts through vaccination and immunity support.

Category of infectious disease & its disease:

• Blood/Vector Borne: Dengue Hemorrhagic Fever (DHF), Malaria, Leptospirosis, Filariasis
• Enteric: Typhoid Fever, Viral Hepatitis, Schistosomiasis
• Eruptive: Measles (Rubeola), Varicella, German Measles (Rubella), Smallpox
• Respiratory: Pneumonia, Diphtheria, Pulmonary Tuberculosis (PTB), Mumps
• CNS: Encephalitis, Meningitis, Meningococcemia, Rabies, Tetanus, Snake Bite
• Diarrheal: E. coli, Staphylococcus aureus, Cholera, Rotavirus, Salmonella, Parasitism
• Emerging: SARS, Bird Flu

Dengue Hemorrhagic Fever (DHF) - Category 1

• Overview: Pathogen: Flavivirus (Dengue Virus 1, 2, 3, 4); Vector: Aedes aegypti, Incubation Period: 3 to 10 days
• Clinical features: Herman's rash
• Severity: Mild Dengue & Severe Dengue (DHF/DSS)

Preventative measures for DHF

• S strategy
• Search, Self-protection, early consultation, saying no to indiscriminate fogging

Malaria

• Spread through anopheles mosquitos that prefer slow moving streams
• Some species like P. malariae can lay dormant for years
• Clinical Manifestations: High fever, chills, and sweating
• Stepladder fever

Filariasis (Elephantiasis)

• debilitating parasitic disease caused by microscopic thread-like worms affecting the lymphatic system
• causes swelling and dysfunction

Leptospirosis

• zoonotic systemic infection spread through infecting by contaminated animal urine
• also known as weil's disease

Summary of Hepatitis

Transmission

• Hepatitis A and E: Fecal-oral route.
• Hepatitis B, C, and D: Blood/body fluids.

Serology

• Hepatitis A:Acute only.
• Hepatitis B, C, and D: Chronic possible.

Eruptive Fevers

Symptoms & Diagnosis

• Diagnosed through serologic tests.

Smallpox

• caused by Poxvirus and diagnosed with clinical evaluations.
• prevented with Pre-exposure vaccination

Category 4: Respiratory Diseases Overview

Meningococcemia

• Caused by Neisseria meningitidis.
• Is droplet route/ Airbourne.
• Causes fever, chills, and arthralgia
• Can cause ptetechial, purpuric, or ecchymotic rash/ Fulminant Meningococcemia
• Antibiotics: Benzyl Penicillin and can cause a septic shock
• Provide a Strict aseptic technique

Tuberculosis

• Infection that can be droplet route from sputnum, coughing, and sneezing
• People can have a cough, afternoon fever, night sweats, and weight loss
• Can cause Pulmonary Fibrosis
• Doctors treat patients using DOTS
• They provide Strict Medication compliance

Cholera

• Causative agent: Vibrio cholerae, Vibrio el tor
• People experience "rice-water" diarrhea and it comes from a fecal-oral route
• Antibiotics include: Furazolidone,Cholramphenical

Salmonellosis

• Causative agent: salmonella spp.
• Signs and symptoms: Nausea, vomiting, abdominal cramps, chills, bloody & mucoid diarrhea with fecal-oral
• Doctors provide dietary support

Rabies

• can be deadly and it comes from animal bites
• pre & post exposure prophyaxis can be given as prevention