Epi Flashcards
The survival of microbial pathogens w/in a human populations is due to what?
the ability for the pathogen to:
- Escape from one host
- Survive and disperse in the external environment
- Invade another host
Mechanisms of infections
- Contact infection:
a. Congenital
b. Sexual
c. other - Air-borne infection (mainly through inhalation)
- water and food-borne infection (mainly via ingegestion)
- Trauma-mediated infection
a. Implantation
b. Injection
Contact Infection
Infection that requires direct person-to-person contact; may involve indirect contact through contaminated articles.
Congenital Contact infection
Being born w/ infection, either through being Transmitted across the placenta or acquired from the mother during birth.
-most infections cant cross the placenta barrier except for some
Ex: HIV, rubella, syphilis, toxoplasmosis, cytomegalovirus.
-Gonorrhea acquired during delivery.
Sexual Contact Infection
From one person to another directly by mucous membrane contact or shared body fluids.
Ex: STIs, hep b, HIV
Other Contact infections
- Non-sexual: 1 on 1 contact such as hugging, shaking hands
- Autoinfection: infection on one-self such as E.coli, and boils
- Fomites: acquired through contact w/ articles contaminated by another person such as athletes foot, cold sores (sharing cups!!)
Air-borne infections
Transmitted mainly by the disposition of the moist mucous membrane of the nose pharynx, trachea, and bronchial tree during inhalation.
-must be present in sufficiently small particles that can be easily transmitted through the air.
a. Air-borne droplets
b. Air-borne dried particles
Ex: Diptheria, TB, whooping cough, measles, flu, the common cold
Air-borne Droplets
Droplets from a sneeze or cough (aerosol cloud of droplets can be seen and felt). However, mainly saliva is heavy so it drops quickly to the floor.
Air-Borne dried particles
Main Vehicle for transmission of air-borne infection.
derived from nasal mucus or septum (the actual site of infection), which in moist form can spread easily on skin, handkerchiefs, clothing, bedding, etc. when dried and disturbed, dried particles are released into the atmosphere ( motes). Can see motes in sunlight shafts, and allows the infection to occur over much greater ditances.
Water and food-borne infections
Results from ingestion of faecally contaminated food or water; infections affect small or large intestines, but some can spread to other body parts (polio or typhoid)
- Dysentery (shingella dysenteraie)
- Cholera (vibrio cholerae)
- Typhoid (Salmonella Typhi)
- Poliomyelitis (virus)
Proper water treatment( filtration, chlorination, routine monitoring) and correct sewage treatment and disposal are central to good public health. (not always possible for developing communities)
- Can break down due to natural or artificial disasters.
- proper hygiene is important in food preparation and processing.
- Gastroenteritis in NZ
Trauma-mediated infection
Infection through trauma where skin integrity of the body is lost. Two types: Implantation and Injections
Implantation trauma-mediated infection
accidental trauma to deliberate surgical procedures expose sterile tissue to pathogens. Ex: Staphylococcus aureus, pseudomonas aeruginosa, haemolytic streptococci.
Serious tissue damage may also create ideal conditions for germination of the spores introduced pathogenic obligate anaerobes ex: Clostridium perfringens or tetani.
Injections Trauma-mediated infection
penetrations of skin introducing micro-organism into under-lying tissues w/o major disruption of outer body layers.
-Natural: usually infected by vectors. Ex: malaria (plasmodium spp) Bubonic plague (yersinia pestis), dengue fever, yellow fever.
Animal bites the puncture rather than rip ex: rabies
-Artificial: From on person to another via needles, syringes, blood to blood products. infections that can spread this way are Hep-B and C, HIV malaria.
Epidemiology
the study of the factors and mechanisms that influence the distribution and frequency of disease.
Incidence
of new cases of a disease in a specific period of time. a good measure of the progress of disease outbreaks.
Prevalence
of ppl infected by disease at any one time. a good measure of how seriously the disease is affecting the population.
Morbidity Rate
of cases of a disease in relation to totally pop. size usually expressed as # of cases/100,000 ppl/ year
Mortality Rate
of deaths caused by a particular disease. usually expressed as # of cases/100,000 ppl/ year
Types of Epidemiology investigations
- Descriptive epidemiology
- Analytical epidemiology
- Experimental epidemiology
Descriptive epidemiology
studies a wide range of data collected, including # of cases, location, time frames of an outbreak, and details of ppl affect (age, gender, race, socio-economic status, occupation, marital status, etc. )
Patterns:
-Who is more susceptible? (age, race, gender)
-Socio-economic status? are they under-nourished individuals or living in over-crowded or sub-standard housing?
-Occupation info taces back to a factory, slaughterhouse, or hide-processing plant
-If the outbreak is primarily with stick farmers and vets, likely to be an animal sources
-Geographic distribution may indicate contaminated water supply, where a certain vector is located, and restaurant where a Hepatitis carrier works.
Analytical epidemiology
Focuses on establishing quantitative relationships in epidemiology. Looking for factors that might lead to an outbreak. ex: blood transfusion vs those who didn’t get transfusions to establish a link to hep c infection outbreak
Experimental epidemiology
The development of a hypothesis about a disease then can be tested. The use of prophylactic antibiotic therapy to reduce meningococcal disease in identified at-risk groups.
Sporadic disease
A disease that occurs occasionally w/in a pop. There are long periods of time when completely absent from pop.
ex: tetanus and botulism
Endemic disease
A disease that’s constantly present w/in a pop. # of cases fluctuates over time but never reaches zero. Ex: chickenpox and the common cold
Epidemic disease
A short-term increase in the occurrence of a disease in particular pop.
Ex: flu or whooping cough
Pandemic disease
is an epidemic of international or global distribution.
Ex: HIV in 1980’s
Spanish flu in 1919 (killed more ppl that WWI)
Public Health Organisations (PHO)
widespread recognition of the importance of controlling infectious diseases. There are local, national, international, and global levels.
- WHO
- CDC
- CDC Welly
- Local reporting
WHO
Organization based in Geneva. Develops, coordinates, and implements programs to improve health in 100 countries
- set health standards
- assist member countries to mount effective control and immunization programs
- maintains surveillance for potential epidemics
- Collects, analyses, and distributes data relation to human health
- provides training and research programs for health personnel, especially in developing countries.
Center for Disease Control (CDC)
US public health, but also functions internationally. Primary functions are to monitor, control, and prevention of infectious diseases. Played a major role in the investigation of the epidemiology of HIV/AIDS
Communicable Disease Centre (CDC Welly)
Linked to the Ministry of Health and responsible for gathering and disseminating data relating to infectious diseases in NZ.
Also monitors overseas trends and provides advance warning of potential influence on NZ.
-produces relevant publications including monthly summary of recent infectious disease data in NZ in NZ public health report.
Local reporting
Under Health ACT 1956, clinicians are required to report all cases of those diseases classified as “notifiable” to MoH. Notifiable diseases updated 2017.
-Local authorities Ex: getting salmonella from the restaurant, to shut it down.
Local infection
Invading micro-organisms limited to small area of the body. Ex: conjunctivitis, boils
Systemic (generalized) infection
Micro-organisms are distributed throughout the body by blood or lymphatic system.
Ex: Typhoid fever
Bacteremia
Presence of bacteria in the blood
Septicemia
bacteria multiplying in blood
Primary Infection
Infection which causes initial illness
Secondary Infection
caused by an opportunist after primary infection has weakened the body’s defenses.
-2ndary infections of skin and respiratory tract are common, and sometimes more dangerous than primary.
Ex: Steptoccal bronchopneumonia following Whooping cough, measles, or flu
Sub-clinical (inapparent) infection
does not cause any noticeable illness. Asymptotic. Ex: Hep B. typhoid mary
Communicable diseases
any disease thats spreads directly from one person to another, directly or indirectly
Non-communicable diseases
caused by normal flora or by organisms that reside outside the body
-tetanus
Contagious diseases
Easily spread from one person to another
-chickenpox
Acute diseases
Develops rapidly but generally lasts only a short time.
-flu
Chronic diseases
develops more slowly and is likely to be continuous or recurrent for long periods.
-TB, thypoid (mary)
Latent diseases
the causative agent remains inactive for long periods of time, and becomes active to produce symptoms of the disease
ex: Cold sores from Herpes simple virus, shingles.
Reservoirs of infection
Sites in which viable infection agents remain alive and from which new infections of individuals may occur. A) Living Reservoirs 1. Human 2. Animal 3. Insect (vectors) B) Non-living reservoirs: surviving in environment between hosts 1. Soil 2. Air 3. Food D. Water
Living Reservoirs: Human
- the main reservoir of infection for other ppl.
- Obviously sick people but controlled by isolation and treatment to minimize spread.
- Carriers: ppl with only mild illness or with no signs of illness. “ Asymptomatic” can still pass pathogens
- Transient Carrier: when the disease is communicable during incubation or recovery period but shows no signs of disease.
- Chronic Carrier: Where the infections persist for long periods of time. Ex: TB, gonorrhea, Hep-b, MRSA, typhoid
Living Reservoirs: Animal
Zoonoses!
mainly occurs in wild or domestic animals that can be transmitted to humans (zoonoses).
- acquired through handling animals, animal products, and receiving bites from blood-sucking insects that prey on both humans and animals.
- Major reservoir due to the fact of 150 recognized zoonoses
ex: rabies, anthrax, brucellosis, leptospirosis, toxoplasmosis, bubonic plague, yellow fever - complicates disease control, more difficult to eradicate diseases.
Living Reservoirs: Insect Vectors
- Sucking Mamminlain blood as food meets the demands of laying many eggs (protein-demanding) making only email insects doing the biting.
- a disease transmitted but vector but mico-organisms have complex life cycles in which the human host is only one part.
- Fleas: Bubonic plague
- Mosquitoes: malaria, yellow fever, filariasis, dengue fever, Ross River fever
- Bed: Chagas’ disease
- tsetse flies: sleeping sickness
- Body lice: epidemic typhus
- Ticks (arachnids): Rocky mountain spotted fever, q fever, and lyme disease.
- Mites (arachnids): scrub typhus
Non-living reservoirs: soil
- clostridium botulinum spores
- clostridium tetani spores
- certain fungi that can cause mycoses (coccidioidomycosis)
- infective stages of larger parasitic organisms (nematodes)
Non-living reservoirs: air
- just “passing through” but a major reservoir of human infectious diseases because it is continually being contaminated by:
- dust from soil
- dust from humans ( skin scales, dried nasal mucus and sputum)
- droplets from coughs and sneezes
- droplets and dried particles from other body products (gastro-intestinal tract, infected wounds)
Non-living reservoirs: food
- Primary reservoir: disease being transmitted directly from the animal being eaten ex: salmonella in eggs or chickens, parasitic worms (tape worms, flukes, and nematodes) from poorly cooked beef or pork.
- Secondary reservoir: when food itself becomes contaminated by new organisms that reproduce. Ex: staphylococcal food poisoning.
Non-living reservoirs: water
- in places human sewage disposal is inadequate and water treatment is poor or absent.
-pathogenic org. comes directly from diseased digestive tracts, followed by drinking contaminated water
EX: dysentery, cholera, typhoid, poliomyelitis, hep-A, giardiasis, cryptosporidiosis, leginnaire’s disease, amoebic meningitis.
-during natrual disasters and major social upheaval, water and sweage can be disrupted. Epidemics of water-borne disease can quickly cause more suffering than original disaster.
Nosocomial infections
hospital-acquired infections. -infections that were not present upon admission. -Constant hazard w/in hospital environment and may occur: patient to patient staff to patient patient to staff staff to staff auto-infection
Main Categories of hospital-acquired infections?
(variations between one location to another and different times of year)
- UTI
- Surgical wound infections
- Respiratory tract infections
- blood, skin, and other infections
UTI
- accounts for 40-50% of all nosocomial infections
- associated with urinary catheterization (contaminated cath., inadequately cleaned insertion site, movement of organisms from leaky connections.
- very common
Surgical wound infections
Post-op surgical wound infection accounts for 15-25% of nosocomial infections.
- exposes sterile tissue to air/instruments/personnel that can carry pathogenic organisms.
- Long complex surg. increase the risk of subsequent post-op infections
- Amputations and bowel surg especially likely to cause post-op infection
Respiratory Tract infection
15-30% if nosocomial infections.
-related to the use of respiratory devices that administer air/O2/medication to the lungs.
-Pathogens grow in fluid reservoirs of cold mist and warm steam humidifiers. organisms can dispense during normal operation.
Ex: babies, ICU (those on ventelators),
Blood, Skin, and other infections
10-20% nosocomial infections.
- Bacteremia and septicemia are usually associated with IV catheterization.
- Burn pt and neonates are especially prone to skin infections.
Where do most micro-organisms that cause nosocomial infections come from?
Primarily micro-organisms from pt. own normal flora, from other pt. normal flora, and from normal flora of the staff.
About half of all nosocomial infections are caused by which 4 bacteria?
Escherichia coli, Staphylococcus aureus, Streptococcus pyogenes, Pseudomonas aeruginosa
other 50% from a wide range: -Staphylococcus epidermidis -klebsiella spp -Enterobacter spp ect.
Current/ recent infectious disease problems in NZ
-a total of 16,305 notifiable diseases in 2016
-Rheumatic fever
-TB
-Meningococcal disease
-food-borne disease
-mMRSA
HIV/AIDS( only AIDS on notifiable disease in NZ list)
Nz immunization schedule was last updated what year?
oct 2020
What vaccines are part of the immunization schedule when a woman is pregnant?
Influenza
Tetanus/Diptheria/pertussis
What vaccines are part of the immunization schedule at the age of 6 weeks?
Rotavirus
Diphtheria/tetanus/Pertussis/polio/Hep B/ Haemophilus influenza type B
Pneumococcal
What vaccines are part of the immunization schedule at the age of 3 months?
Rotavirus
Diphtheria/tetanus/Pertussis/polio/Hep B/ Haemophilus influenzae type B
What vaccines are part of the immunization schedule at the age of 5 months?
Diphtheria/tetanus/Pertussis/polio/Hep B/ Haemophilus influenzae type B
Pneumococcal
What vaccines are part of the immunization schedule at the age of 12 months?
MMR (Measles/mumps/rubella)
Pneumococcal
What vaccines are part of the immunization schedule at the age of 15 months?
Haemophilus influenzae type B
MMR
Varicella (chickenpox)
What vaccines are part of the immunization schedule at the age of 4 years?
Diphtheria/tetanus/Pertussis/polio
What vaccines are part of the immunization schedule at the age of 11-12 years?
Diphtheria/tetanus/Pertussis
Human Papillomavirus (HPV)
What vaccines are part of the immunization schedule at the age of 45 years?
Diphtheria/tetanus/Pertussis
What vaccines are part of the immunization schedule at the age of 65 years?
Diphtheria/tetanus/Pertussis
Zoster (shingles)
Influenzae
