Communicable Diseases: Types and Epidemiology

• Communicable diseases result from infectious agents, acquired from an infected source and transmitted to a susceptible host through direct/indirect contact or inoculation.

Key Components

• Infectious/causative agent.
• Two individuals: one infected, other susceptible.

Types of Communicable Diseases

• Infectious diseases require inoculation and aren't easily transmitted from person to person.
• Inoculation: when microorganisms enter through mechanical means (breakage).
• Intact skin and mucous membranes are the first line of defense.
• Mechanical entry: incision, laceration, biting, puncturing, injury.
• Tetanus, malaria, dengue, filariasis, rabies, schistosomiasis are examples.
• Contagious diseases are easily transmitted through airborne/droplet, direct, or indirect contact
• Examples: TB, diphtheria, measles, chickenpox, meningococcemia.

Epidemiology

• Epidemiology investigates disease patterns, distribution, and spread.
• It focuses on public health, including prevention and control in groups.
• Activities include describing pattern, occurrence, distribution, spread, prevention and control.

Disease Occurrence Patterns

• Sporadic: intermittent attacks, where 80% are immune and 20% susceptible.
• Endemic: disease constantly present in a specific locality, with typically a 50/50 immune/susceptible ratio.
• Epidemic: number of cases exceeds normal expectations, illustrated by 80% susceptible in many regions.
• Examples of endemic diseases in the Philippines: malaria, filariasis, and schistosomiasis.
• Pandemic: a worldwide epidemic or occurrence exemplified by AIDS, SARS, Bird Flu, COVID-19.

Epidemiologic Triad

• Agent, host, and environment interact to cause disease.
• Removing one factor prevents disease.
• Agents: bacteria, viruses, fungi, protozoa, parasites.
• Pathogenicity: 3% of agents are pathogenic.
• Infectivity: agent's ability to enter and move within the body.
• Virulence: agent's potency or strength to cause disease.
• Antigenicity: agent's ability to stimulate an antibody response.
• Vaccination: creates antibodies to protect against microorganisms.
• Pathogenicity: ability to cause infection or disease.
• Environment: supports agent survival and multiplication.
• Host: area where agent gets nourishment.

Hosts

• Carriers (asymptomatic): harbor microorganisms, not showing symptoms, most dangerous.
• Sub-clinically ill: general symptoms, less dangerous.
• Clinically ill: manifests all symptoms, least dangerous.
• Animals: serve as intermediate hosts (vectors).
• Plants, soil, water, air, milk can also be hosts.
• Fomites: inanimate objects, e.g., stethoscope, thermometer.

Chain of Infection

• Agent: causative agent releasing toxins inside or outside the cell.
• Exotoxin: found outside living microorganisms.
• Endotoxin: found inside dead microorganisms.
• Reservoir: infection source where the organism is found.
• Portal of Exit: how the agent leaves the reservoir.
• Respiratory system allows for coughing/sneezing.
• GIT/alimentary tract releases vomitus or feces.
• GUT releases urine, semen, vaginal discharges.
• Skin open wounds.
• Mechanical entry: insect or animal bites.
• Blood: broken skin or mucosa.
• Transplacental route: from mother to fetus.
• Exudates or discharges: conjunctival, saliva, pus.
• Mode of Transmission: how microorganisms are transmitted.
• Direct: person to person, intimate contact needed, as in sexual intercourse or droplet spray (coughing, sneezing).
• Distance for droplet transmission: 3 feet/1 meter.
• Airborne: over 1 meter.
• Droplets transmit within 30 minutes.
• Airborne transmits longer than 30 minutes.
• Indirect: vehicle or vector borne via milk soil or animals.
• Portal of Entry: corresponds to exit.
• Susceptible Host: prone individuals.

Disease Stages

• Incubation: the time between first exposure and first signs/symptoms.
• Prodromal/Catarrhal: period from first symptoms to pathognomonic signs.
• Illness: when all signs/symptoms manifest.
• Convalescence: recovery, symptoms gradually disappear.
• Immunity: body's resistance to infection.

Immunization & Immunity

• Immunization: process of making individuals immune.
• Antigen: induces antibody formation.
• Antibody: protein developed in response to antigen.
• Natural immunity: inborn, innate, inherent.
• Active: exposure to disease and memory cell formation.
• Passive: maternal antibodies via placenta/breast milk (IgA).
• Artificial immunity: through antigen introduction (vaccine, toxoid, antibody).
• Active type done through vaccine/toxoid introduction.
• E.g. all EPI vaccine except Hepa B.
• Passive type done through antibody introduction: IgA, gamma globulins.
• Active immunity is slow to develop and slow to go.
• Passive immunity is quick to come and quick to go.

Prevention & Control (RA 3573/RA 11332)

• Addresses how to report communicable diseases.
• Prevention through health education, environmental sanitation, and specific protection.
• Control by notification, prompt intervention, isolation, and epidemiological investigation.
• Isolation is used for separating infected individuals from healthy ones.
• Quarantine limits the movement of exposed individuals.
• Case finding looks for infected individuals for quarantine.
• Contact tracing identifies and finds the exposed.

Epidemiological Investigation Plan

• Establish presence of epidemic, verify diagnosis, and analyze reporting and prevalence.
• Establish time/space relationship: concentration areas, onset times, spread duration.
• Relations to community characteristics: age, sex, color, occupation.
• Correlation of collected data.

Isolation Types

• Isolation: separating infected individuals.
• Strict: for highly contagious diseases like SARS.
• Protective/Reverse: for immunocompromised. Example: AIDS, cancer, transplant.
• Respiratory: used for respiratory diseases.
• Enteric: for GIT diseases, fecal-oral transmission.
• Wound/Skin (Contact): for skin diseases.
• Blood/Body Fluids/Standard/Universal: for blood-borne diseases.
• Gloves, masks, caps, gowns, and goggles are needed.
• Quarantine: limits movement of exposed individuals.

Disinfection

• Disinfection: destroys pathogenic organisms, excluding spores.
• Sterilization: destroys all microorganisms, including spores.
• Delousing: killing lice.
• Fumigation: destroys pathogens with fumes.
• Mechanical: sterilization through boiling.
• Chemical: disinfectants for inanimate objects and antiseptics for living tissue.
• Concurrent: ongoing disinfection while patient is infectious.
• Terminal: final disinfection when patient is no longer infectious.

Asepsis

• Asepsis (Aseptic Technique): Absence of pathogens.
• Medical/Clean: hand washing (hands lower than elbow), preventing pathogen transfer.
• Surgical/Sterile: surgical hand washing (hands higher than elbow)
• Tuberculosis
• Consumption, Koch's disease, Phthisis. Causative agent: Mycobacterium tuberculosis.
• Mycobacterium bovis (source of BCG Vaccine) Transmission: airborne droplets.
• Incubation: 4-6 weeks. Pathognomonic signs: low grade fever, night sweats, loss of appetite and weight.
• Diagnostic test: Sputum Examination, Chest X-ray, tuberculin testing

Sputum Examination

• Confirmatory test.
• Directly examines/tests sputum with acid. First step is directing Sputum Smear Microscopy, also known as DSSM.
• Early morning sputum, about 3-5 cc.
• NPO must be maintained before collecting the specimen.
• Oral care must be given after the procedure.
• Specimen must be labeled and sent ASAP.

Chest X-ray

• Used to determine clinical activity (active/inactive TB) and lesion size (minimal, moderate, or far advanced.)

Tuberculin test

• Determines history exposure of TB.
• Uses PPD (purified protein derivative).
• If exposed to TB, they will have PPD leading to indurations of >10mm.
• Interpretation: Induration sizes indicate exposure (5mm, 5-10mm, >10mm)
• Mantoux Test: individual screening, read after 72 hours.
• Tine test: Mass screening and should be read after 48 hours. Treatment for TB includes DOTS which is the Direct Observed Treatment Short Course.
• The Chemoherapy includes Rifampicin, Isoniazid, Pyrazinamide, Ethambutol (Oral), and Streptomycin (IM) .
• Rifampicin can cause orange-colored urine and is hepatotoxic.
• Isoniazid causes peripheral neuritis.
• Pyrazinamide can cause hyperuricemia/gouty arthritis.
• Ethambutol will cause optic neuritis.
• Streptomycin also damages the 8th cranial nerve, ototoxic, nephrotoxic. For TB, the mode of transmissions hould be avoided by covering with face whenever you are coughing or sneezing. There are helth education protocols.

Diphtheria

• Big throat - swollen neck (Bull neck).
• CAUSATIVE AGENT is Corynebacterium diphtheriae Klebbs - Loffler bacillus
• The MODE OF TRANSMISSION is through direct contact with droplets.
• Incubation : 2-5 days.
• PATHOGNOMONIC SIGNS: a white membrane on the oropharynx.
• Diagnostic tests include Nose and throat swabs to culture and determine hypersensitivity and schick's test.

Pertussis

• AKA whooping cough, Tusperina No day cough.
• CAUSATIVE AGENT Bacteria Bordetella.
• MODE OF TRANSMISSION, droplet discharges
• Incubation period 7 - 10 days but not exceeding 21 days
• PATHOGNOMONIC SIGNS Catarrhal period is 7 days.
• Diagnostic test: : Bordet - Gengou agar test

Tetanus

Characteristics of Tetanus includ Lock Jaw.

• CAUSATIVE AGENT: Clostridium tetani MODE OF TRANSMISSION indirect contact through soil
• Incubation period 7 - 24 days
• There is no test - just a history of being punctured. Treatment Antitoxin, and to avoid specific infection - PREVENT

Poliomyelitis

• Characteristics: affects lower extremities and can result in deformity.
• Agent CAN result in a fever.
• MAN is only resevoir.
• Transmission: Fecal-oral route Symptoms: Muscular weakness, no motor control.
• Refer for rehab

Measles

• Names: Tigdas, Rubeola, Morbilli CAUSATIVE AGENT RNA paramyxovirus
• Transmission is droplets. Period: 4 days before +5 days after
• Koplick spots : inside of mouth, rash Management - supportive.
• prevent.

Hep B

• Permanent Condition.
• HBAg test
• Management - supportive
• Prevention.

Illness from Food and water

They are transmitted form improper contact.

Cholera

• Agent: vibrio cholera, coma
• Transmission" Fecal-oral Pathonogmomic sign is rice watery stool
  Prevention: Proper sanitation,
• Treatment ORESOL is added because it has lots of minerals\

Anoretic Dysentry

• CAUSATIVE AGENT- Entamoeba Histolytica. Prevemntion - sanitation
• Treat with a flagyl

Shigellosis

Dysentery is common

• Agent: Dysentery
• Pathognomonic signs is abdominal cramping and and mucoid stool Treatment: Cotrimoxazole.

Typhoid fever

• Agent: Samonella typhosa. Transmission = transmission, prevent: PROPER sanitation of food and water

Para shell fish poisoning!

Agent; Dinoflaggellates.

Syphillis

• Agent :Treponema Pallidum SignsL- transmission- blood

Gonorreahoe

• Tulo and Gleet are forms. Nesseria gonorehoa is the agent

Chlamydia

• Trachomatis chlamydia is the result form this transmissioln, Womwn= asymptomatic Treatment: Erythrmyosin. and erythtromycin. Treatment-

Aid

• Causative Agent: T cell
• Severe malnutrition Transmisssion- contact.

Moniliasis/Candidiasis

Agent - Albicans

• Pathononomimc signs = vaginal issueses.

Ehruptive disases

• Causes vessicles to appear - Self LImiting
• Incubation period: 2- 3 Weeks. Sign - Central appearance.

Herpes ZOster

Clusertered Vessicles- Painfull

4H" Dengue

Causative agent- Dengue virus Transmission. mosquito Bities

Malaria

Signs intermittent chills and sweating

Lepproposy- Long term

• Skin disorder

Anthrax

Can come from skin - Spores can live long

Meningitis

.Agenic Agents Transmission Causattions = Earache symptoms

-Transmission- contact. Agenic Agents Trabsmission Causattfion- earaache sympptoms