Epidemiology of Communicable Diseases

• Public Health involves sciences, skills, and beliefs for maintaining and improving people's health.
• It includes societal efforts to protect, promote, and restore health through collective or social actions.

Epidemiology of Communicable Diseases

• Epidemiology studies factors related to the incidence and spread of diseases.
• Etiology refers to the causative agent of a disease.
• Communicable diseases can be transmitted directly or indirectly between humans, animals, or insects.
• Infection involves a host-parasite relationship, potentially leading to disease or immunity.
• Infestation refers to the lodgment, development, and reproduction of arthropods on the body surface, as seen with lice.
• An epidemic is a disease outbreak in a community exceeding expected cases e.g. cholera in Egypt in 1948.
• Common source epidemics involves infections from a shared source.
• Propagated epidemics involves person-to-person spread with a slower increase and decrease in cases.
• A pandemic is an epidemic occurring over a wide geographic area, globally e.g. plague in wars.
• Endemic presence is the habitual presence of a disease in a community e.g. bilharzia in Egypt.
• Sporadic cases are infrequent and scattered occurrences of a disease in a community.
• Herd immunity is community immunity that increases with a greater number of immune individuals.
• Zoonotic infections are transmitted from animals to humans under natural conditions.
• Nosocomial infections are acquired in a hospital setting e.g. from pseudomonas or hepatitis B.
• Occupational infections are associated with specific professions and are often zoonotic.
• Infection transmission involves interactions between humans, animals, and the environment.
• The elements Pathogens, intensify and interact with each other

Disease Transmission Links

• Disease transmission involves a reservoir, a mode of transmission, and a susceptible host.
• The reservoir is where the infectious agent lives and/or multiplies.
• The source or reservoir of infections can be non-living, human, or animal.
• Mode of transmission is how the agent travels from the reservoir.

Human Reservoirs

• Human reservoirs can be either clinical, subclinical, or carriers.
• Carriers are individuals who harbor and shed the infectious agent but show no symptoms.
• Carriers is the most dangerous infection reservoir.
• Carriers might be unaware of their infection status, leading to widespread contacts.
• Chronic carriers can serve as a source of infection over a prolonged period.
• Carriers are important because their numbers may outnumber the sick, and neither they nor their contacts may take precautions.
• Classified as passive carriers who are not infected or active carriers who may or may not exhibit symptoms.
• Carrier classification includes type, duration, and portal of exit.

Types of Carriers

• Incubatory carriers shed the pathogen during incubation, specially last days of the incubation period e.g. mumps, measles, diphtheria.
• Convalescent carriers shed the pathogen during convalescence e.g. typhoid, dysentery, whooping cough.
• Healthy carriers receive the infection from another carrier.
• Temporary carriers shed the pathogen for a short period.
• Chronic carriers shed the pathogen for indefinite periods which can be dangerous.

Portal of Exit for Carriers

• Respiratory carriers shed pathogens through the respiratory tract e.g. influenza.
• Fecal carriers shed via feces e.g. typhoid, dysentery, cholera.
• Blood carriers shed via blood e.g. hepatitis B, AIDS.
• Urinary or sexual carriers shed via urine or sexual contact e.g. gonococcus, AIDS.
• Animal reservoirs are animals or birds e.g. rabies, brucella from animals and psittacosis from birds.
• Soil reservoirs includes soil where tetanus, gas gangrene, and anthrax reside.
• Animal and soil reservoirs are very difficult to eradicate.

Modes of Infection Transmission

• Direct droplets are those sprayed through saliva and nasopharyngeal during coughing, sneezing or talking; pneumococcus, diphtheria, T.B.
• Airborne transmission may occur through droplet nuclei (dried residues of droplets e.g. T.B) or dust (settled droplets e.g. TB, psittacosis)
• Fomite-borne transmission spreads diseases by way of towels, spoons, cups, etc.
• Food and water transmits follows the route: feces-flies-food-fingers (4F).
• Flies transmit infection mechanically e.g. trachoma.
• Bacterial infection e.g. from typhoid, dysentery, and cholera.
• Viral infection e.g. from hepatitis A and polio.
• Parasites e.g. Entamoeba.
• Arthropod transmission transmits biologically.
• Fleas transmit plague and endemic typhus.
• Mosquitoes transmit yellow fever and malaria.
  • Ticks transmit endemic relapsing fever
• Contact involves a direct transfer through kissing or sexual intercourse e.g. infectious mononucleosis.
• Bacteria e.g. Gonorrhea, Syphilis.
• Virus e.g. Herpes simplex type II and AIDs.
• Transmission can occur through parenteral or blood transfusion e.g. hepatitis B and C, AIDS.
• Animals can transmit trough bites e.g. rabies.
• Transmission can occur through a transplacental infections that is bacteria/virus during pregnancy; Syphilis, AIDs, Rubella.

Epidemiology as a Medical Science

• Epidemiology is a fundamental medical science studying the distribution, frequency, and control of diseases in human populations.
• It analyzes disease distribution patterns, aiming for prevention and control.
• Epidemiological studies can be descriptive or analytical.
• Analytical studies can be separated into observational or experimental.

Descriptive Studies

• Descriptive studies observe disease distribution in a community, collecting data from surveys or health authorities.
• Data should include # cases, affected people, location, time, age, socioeconomic level, job, and marital status.

Analytical Studies

• Analytical studies aim to show the relationship between a disease and a predisposing factor e.g. cancer and asbestos.
• Studies may be prospective in order to collect future occurrence or retrospective in searching previous data.

Retrospective Studies

• Retrospective studies, also called case control studies, compare a "case" group (suffering from a condition) with a "control" group (without) to identify past exposures or risk factors.

Prospective Studies

• Prospective studies, also called control or cohort studies, follows a study group and a control group into the future; they are more tedious, but more accurate.
• "Study group" would have individuals exposed to risk e.g. smoking.
• "Control" is the comparable group who is unexposed to the same risk.

Quantitative Analysis of Data

• Data from studies are analyzed via incidence rates of outcome and estimation of risk.
• Experimental studies use two groups, a study and control, to show the effect of a new drug or vaccine.
• Reported in terms as Relative Risk

Incidence Rate Calculation

• The formula for Rate of Incidence is Number of infected persons X 100, divided by population at risk.
• Incidence data indicates the spread of a disease.
• Prevalence data measures the seriousness and duration of a disease.

Hospital Acquired Infections

• Hospital acquired infections, also known as nosocomial infections, are derived from patients, staff, or the environment.
• Common Bacterial infections, these include; E. coli, hemolytic Streptococci, Staphylococcus aureus and Pseudomonas aeruginosa.
• Factors favoring nosocomial infections include the hospital environment, patient susceptibility, and medical procedures.

Predisposing Factors

• Susceptible patients include the very young and elderly or patients with illnesses, i.e. HIV or cancer treatments which hinder the immune system; those patients are highly susceptible.
• Microbial factors in hospitals are highly pathogenic and drug-resistant so they can cause infections in immunosuppressed patients
• Medical procedures involve the penetration of protective barriers and often the introduction of devices, increasing infection risk.

Sources of Pathogens

• Nosocomial infections can be divided into two general categories based on; the source of the causative organism, i.e. exogenous or endogenous
• Exogenous infections are caused by microorganisms from a source external to the patient such as persons, inanimate objects, environmental sources (water or disinfectants).
• Endogenous infections are caused by microorganisms that are part of the patient's own normal flora often colonize there patient/hospital.
• Patients with surgical wounds or accidental injuries are also at risk.

Endogenous Infections

• Endogenous infectious may be from microbes that have since spread to another site or "self-infections".

Control Measures

• Prevention and control of nosocomial diseases includes isolation of cases, disinfection of articles, and sanitation practices.
• Identification involves isolation, microscopic cultural examination, and typing causative agent.

Infection Prevention

• Concurrent disinfection disinfects all contaminated materials during the course of illness, which is immediate.
• Terminal disinfection occurs after recovery/death of patient.
• Key to sanitize via air cleaning, hand washing with antibacterial/viral wash, and wearing personal protective equipment.
• Prevention of diseases takes measures prior to the onset of the disease.
• Disease prevention includes; health protection, health promotion, and specific protection.

General Preventive Measures

• General preventive measures for diseases involve sanitary environments and health education.
• A sanitary environment is one with good water, sanitary housing, food, sewage disposal, and refuse management.
• Health education involves better nourishment and encouraging personal hygiene.
• Specific protective measures control reservoirs and protect susceptible hosts.

Infection Isolation

• Clinical and treatment-based lab diagnosis, as well as isolating persons (cases and carriers), are key factors that prevent infection spread
• Source" Barrier nursing (isolate colonized/infected patients)
• "Reverse Isolation" Prevent transfer microbes/pathogens to avoid super infection.
• Isolation measures are crucial for managing infections with high morbidity, mortality, or infectivity, and easily recognizable cases.
• International agreements Quarantine of contacts of specific infections longer than the infectious incubation period.
• Specific agreements include; smallpox, cholera, plague, yellow fever, typhus fever, and relapsing fever (Recently: Covid 19).

Immunization

• Immunization prevents disease through vaccines and includes the classification for immunization; both active and passive.
• Active: rendered harmless, attenuated i.e. Live vaccines, produce ongoing stimulus/multiplication to immune system

Timing of Vaccination

• Immunization timing includes; BCG given at birth, DPT and polio vaccines, and hepatitis B at multiple months.

Passive Immunity

• Gamma-globulin therapy: involves administration of immunoglobulins for short-term protection.
• Antitoxin therapy: involves administering antibodies against toxins, as in diphtheria and tetanus.

Non-Communicable Diseases

• Non-communicable diseases are typically chronic (long lasting) and include; cardiovascular diseases, renal failure, and liver failure.
• Heart, is characterized via angina, and myocardial infraction, which is one of the most prevelant with at least 25% of deaths.
• Predisposing factors are diet, age,. genetic factors with lack of exercise etc.

Hypertension

• Hypertension, can be caused by lifestyle and genetic factors.
• Liver cirrhosis involves bilharziasis and with persons with alcoholism.

Diabetes Mellitus

• It is a heterogeneous form of hyperglycemias caused by environmental and genetic factors.
• Insulin treatments are dependent for survival.

Cancer

• Cancer can be prevented; this includes maintenance in weight which will also affect stress levels.
• Genetic diseases can be found within embryonic phases.

Nutrients

• Proteins, fats, carbohydrates, and alcohol are classified nutrients which supply the body with energy

Food Classifications

• Provide the body with carbohydrates, fat and vitamins, lipids and minerals.

Proteins

• Required for repair and synthesis of the antibodies in production.
• Also used to provide necessary amino acids.
• Proteins come from both; animal and plant life
• Proteins that come animals are high in value due to higher Nitrogen content.

Carbohydrates

• Very efficient and economical in energy but contains smaller levels of fat.
• Contains starch, glucose, and other carbohydrates to provide energy.

Fats

• Some fat contains amounts of fat such as A and D

Mineral Salts

• Minerals that the body needs include and cannot be synthesized.

Other

• Including molybdenum, boron with obscure effects.

Vitamins

Fats

• Vitamins A, required for optimal cellular function and vision.
• Vitamin D maintains regulation of calcium.
• Vitamin K facilitates normal thrombogensis.

Water

• Thiamine B1, is used in carbohydrate synthesis.
• Riboflavin B, prevents dermatitis.

Malnutrition

• Is caused by lack of balance in diet.
• Can lead to starvation, primary.

Protein

• Affects younger infants and children who have a low amounts of protein, but carbohydrates; an energy based diet.
• Some issues that causes are issues with liver, edema, and/or lack of strength/stamina.

Disfiguration

• Causes include disorders with disarrangements internally.

Diet and Health

• Healthy food and diets can prevent heart issues.
• Intake of energy should be consumed accordingly.

Water

• Safe water with proper drainage and sanitation are key for public health
• Water Impurities like gases, microbes are also important.

Water Impurities

• Water can be from rain, industry, agriculture with minerals.

Water Borne Infections

• Water can lead to dysentery, polio and hepatitis and others.

Dental

• Dental contains high amounts of fluoride.

Methaemoglobin

• Chemical agents may be present which can alter hemoglobin.

Contamination

• Contamination can lead to several conditions from both; animal and human sources leading to diseases.

Indicator

• Bacterial levels can increase by contamination by many means.
• Indicator can be intestinal or bacteria within feces which enter water.
• Chemical bacteria can enter to damage/cause issues which can alter its natural functionality.

Water Supply

• Can lead to unsafe environments due to water being impure.

Bacteria

• Pathogens can create a biofilm and can enter causing infections.

E.Coli

• E.Coli can grow within coliform at a certain temprature.

Waste water

• Sulfite can also create conditions that damage people and create diseases.

Pathogens and Pseudomonas

• Pathogens and pseudomonas can all lead to bad environments.

1. Most probably number involves several processes

iii. The test that is completed: Includes culture.

Method

• Volume of water put into bacteria and put in a membrane the result of the bacterial levels is what the result
• This helps calculate if water.

Milk

• The animal excreta may also be a source of contamination.
• Important to maintain a clean source with no brucellosis or tuberculosis.
• Methylene can be used to show activity and if positive that activity reduces a number of bacteria.

Waste Water

• Sewage can be a large impact when there is bacteria present.

• In waste water both micro and and chemical imbalances as well as bacteria can lead to poor conditions.

Water Sanitation

• Microbes increase in waste and that creates potential pathogen contamination of water that leads into a bad cycle.
• This has to be mitigated to prevent any diseases.