Infectious Diseases and Epidemiology Flashcards
Disorders caused by organisms such as bacteria, viruses, fungi, or parasites
Infectious disease
Cell damage
Disease
Subjective changes that are not seen by the observer
Symptoms
Objective changes that can be observed and measured
Signs
Group of signs and/or symptoms that may accompany a particular disease
Syndromes
The time between infection and
occurrence of the first symptoms or signs of disease.
Incubation Period
A short time of generalized, mild symptoms (such as malaise, muscle aches) that precedes illness. Not all infectious diseases have a this stage.
Prodromal Period
The most severe stage of an infectious disease. Signs and symptoms are most evident during this time. The patient’s immune system has not yet fully responded to the pathogens, and their presence is harming the body.
Period of Illness
The body gradually returns to normal as the patient’s immune response and/or medical treatment eliminates the pathogens. Fever and other signs and symptoms subside. Normally the immune response and its products peak during this stage.
Period of Decline
The patient recovers from the illness, and tissues and systems are repaired and returned to normal
body.
Period of Convalescence
A disease that develops rapidly but last only for a short time
Acute Disease
An intermediate between acute and chronic disease
Subacute Disease
A disease that develops more slowly but may continue for a long time period
Chronic Disease
A disease where the causative agent remains inactive for a moment but then becomes active
Latent Disease
A disease than can spread from one person to another
Communicable Disease
A disease that cannot spread to other hosts
Non-communicable Disease
Limited tp a small area of the body
Local Infection
Spreads through the body via blood or lymphatic system
Systemic Infection
An acute infection that causes the initial illness
Primary Infection
A disease caused by an opportunistic pathogen after the primary infection has weakened the body’s defenses
Secondary Infection
An infection that does not cause notable illness
Subclinical Infection
“Inapparent infection”
Chain of infection
Susceptible Host
Pathogen
Reservoir
Portal of exit
Mode of Transmission
Portal of Entry
Susceptible Host
Elderly
Infants
Immunocompromised
ANYONE
Pathogen
Bacteria
Virus
Fungi
Parasite
Reservoir
ANIMAL RESERVOIRS
HUMAN CARRIERS
NONLIVING RESERVOIRS
Portal of exit
a. In secretions (ear wax, tears, nasal secretions, saliva, sputum, and respiratory droplets);
b. In blood (via arthropod bites, hypodermic needles, or wounds);
c. In vaginal secretions or semen;
d. In milk produced by the mammary glands;
e. In excreted body wastes (feces and urine);
Mode of Transmission
CONTACT TRANSMISSION
VEHICLE TRANSMISSION
VECTOR TRANSMISSION
spread of pathogens from one host to another by direct contact, indirect contact, or respiratory droplets.
CONTACT TRANSMISSION:
CONTACT TRANSMISSION
Direct Contact Transmission
Indirect Contact Transmission
Droplet Transmission
Including person to person spread, typically involves body contact between hosts.
Direct Contact Transmission:
Occurs when pathogens are spread from one host to another by fomites.
Indirect Contact Transmission
objects or materials which are likely to carry infection, such as clothes, utensils, and furniture.
fomites
Pathogens can be transmitted within droplet nuclei (mucous droplets) that exit the
body during exhaling, coughing, sneezing.
Droplet Transmission:
spread of pathogens via air, drinking water, and food as well as body fluids being
handled outside the body.
VEHICLE TRANSMISSION:
VEHICLE TRANSMISSION:
Airborne Transmission:
Waterborne Transmission:
Food-borne Transmission:
Involves the spread of pathogens to the respiratory mucous membranes of a new host via an aerosol, a cloud of small droplets and solid particles suspended in the air that travels more than 1 meter. Aerosols may contain pathogens either on dust or inside droplets.
Airborne Transmission:
Important in the spread of many gastrointestinal diseases. Note this can act as a reservoir as well as a vehicle of infection.
Waterborne Transmission
_________ infection is a major source of disease in the world.
Fecal-oral
Involves pathogens in and on foods that are poorly processed, undercooked or
poorly refrigerated.
Food-borne Transmission:
are animals (typically arthropods) that transmit diseases from one host to another.
VECTOR TRANSMISSION:
VECTOR TRANSMISSION:
Biological vectors:
Mechanical Vectors:
These do not only transmit pathogens; they also serve as hosts for the multiplication of the pathogen during some stage of the pathogen’s life cycle. affecting humans are typically biting arthropods,
Biological vectors
biting arthropods
mosquitoes,
ticks,
lice,
fleas,
blood sucking flies,
blood sucking bugs and
mites.
These are not required as hosts by the pathogens they transmit; they only passively
carry pathogens to new hosts on their feet or other body parts.
Mechanical Vectors:
Pathogens enter the body at several sites, called
Portals of Entry
Portals of Entry
SKIN
MUCOUS MEMBRANES
PLACENTA
PARENTAL ROUTE
The outer layer of of this is composed of relatively thick layers of tightly packed, dead, dry cells and it forms a barrier to most pathogens so long as it remains intact.
SKIN
are capable of burrowing through the skin to reach underlying tissues
larvae of some parasitic worms
can digest the dead outer layers of skin to gain entry to deeper, moister sites.
some fungi
Line all the body cavities that are open to the outside world. Include the linings of the
respiratory, gastrointestinal, urinary, and reproductive tracts, as well as the conjunctiva (the thin membrane covering the surface of the eyeball) and the underside of the eyelids.
MUCOUS MEMBRANES
is the most frequently used portal of entry.
respiratory tract
Some parasitic protozoa, helminths, bacteria, and viruses infect the body through the __________ mucous membranes.
gastrointestinal
The developing embryo forms an organ, through which it obtains nutrients from the mother but because the two blood supplies do not actually contact each other, it typically forms an effective barrier to most pathogens.
placenta
pathogens cross the placenta and infect the embryo or fetus sometimes causing:
Spontaneous abortion
Birth Defects
Premature Birth
A means by which the portals of entry are circumvented (by-pass or avoid).
PARENTAL ROUTE
NONLIVING RESERVOIRS
Soil,
water, and
food
Diseases that are naturally spread from their usual animal hosts to humans are called
zoonoses or zoonotic diseases.
Humans may acquire zoonoses from animal reservoirs via several routes, including:
Various types of direct contact with animals, and their wastes;
By eating animals;
Via bloodsucking arthropods.
means hospital infection
Nosocomial infection
Nosocomial infections result from the interaction of several factors:
Microorganisms in the hospital environment,
The compromised (or weakened) status of the host, and
The chain of transmission in the hospital.
the number of new cases of a disease in each area or population during a given period (such as a month or year).
Incidence
the total number of cases, both new and already existing, in each area or population during a given
period, usually expressed as a percentage of the population.
Prevalence
Epidemiologists keep track of the occurrence of diseases by using two measures:
Incidence:
Prevalence:
a disease that normally occurs continually (at moderately regular intervals) at a relatively stable
frequency within a given population or geographical area.
Endemic
when only a few scattered cases occur within an area or population.
Sporadic
a disease that occurs at a greater frequency than is unusual for an area or population.
Epidemic
if an epidemic occurs simultaneously on more than one continent.
Pandemic
