Definitions 2 for MBI

Epidemiology

The study of diseases in a human population , especially the cause ( etiology ) and transmission of disease

Epidemic

commonly refers to an unusually high incidence of a disease in a community (population) at one time

Prevalence

The proportion of diseased individuals at a given time

Incidences

the number of people affected by a disease

Endemic

a disease is constantly present, usually at low incidence, in a population

pandemic

indicates an epidemic involving more than one continent or a worldwide epidemic

Outbreak

appearance of several cases of a disease, usually in a short period of time, in an area previously experiencing no cases or only sporadic (scattered or isolated) cases of the disease; "mini" epidemic

Morbidity

Disease; sickness: clinical illness

Mortality

Death

Reservoir

a site in which infectious agents remain viable (alive) and from which infection of individuals may occur; a continuing source of disease which may be human, animal, water or soil

Carrier

an infected individual which is not showing obvious signs or symptoms of clinical disease, but which is shedding the etiologic agent for a long period of time (months)

Zoonoses

diseases which occur primarily in animals but are occasionally transmitted to people (plague, Lyme disease, rocky mountain spotted fever)

Vector

living agent which transmits infectious agent (ticks, fleas, flies mosquitoes)

Fomite

non-living object that transmits infectious agents (pencil, doorknob, handkerchief); fomites such as food or water are called vehicles

Communicable disease

a disease that is transmissible among hosts; a contagious disease is one that passes among hosts with particular ease

Noncommunicable disease

acquired directly from environment, not easily transmitted to next host (e.g. tetanus spores

Chain of transmission model

This model explains the spread of a communicable disease from one host (or person) to another. The basic idea represented in the chain of infection is that individuals can break the chain (reduce the risk) at any point; thus the spread of the disease can be stopped. The components of the model typically include:

• The infectious agent (pathogen)

• The reservoir (place where the pathogen normally reproduces)

• The mode of transmission (how the pathogen travels from host to host)

• The susceptible host

Herd Immunity

occurs when a sufficient proportion of a population becomes immune to a disease, either through vaccination or previous infections, reducing the spread of the disease within the community.

Infectivity

The proportion of persons exposed to an infectious agent who become infected by it. It is measured by the ratio of the number of people who become infected to the total number exposed to the pathogen.

Vaccine efficacy

The percentage of protection offered by a vaccine. For example, a ( term ) or effectiveness of 80% indicates an 80% decrease in the number of disease cases among a group of vaccinated people compared to a group in which nobody was vaccinated.

Basic reproduction number (R₀):

of an infection is the expected number of cases directly generated by one case in a population where all individuals are susceptible to infection. In other words, it is a calculation of the average “spreadability” of an infectious disease

Effective reproduction number (R_e

The reproduction number measured when protective measures are used (e.g., vaccination, masks, etc.)

• escape or exit from old host

• travel to new host

• entry into new host

Stages in transmission

What are the modes of transmission

Direct and indirect

Direct transmission

• transmission via

  • close, but not intimate, contact (shaking hands, etc.)

  • intimate contact (sexual contact)

Indirect transmission

• vectors

• vehicles

• fomites

• aerosols

iatrogenic infection

infections caused as a result of medical procedures (catheterization, injection, surgery, etc.) which have a good potential to introduce microbes into patient tissues

Immunocompromised

people are more susceptible than normal ones due to:

• disease - lower resistance due to damage caused by diseases such as AIDS

• treatment - weakened resistance caused by drug therapy for cancer, etc.

• immaturity - newborns are highly susceptible because their immune systems have not yet had a chance to mature and become fully functional

• stress - decreases resistance and immune response development

Transmission - nosocomail

Passing of microbes between patients by hospital personal

Antibiotic-resistant strains

routine use of antibiotics selects for these in hospitals (these strains are frequently resistant to multiple antibiotics)

Immunization of people

• boosters frequently required

• 100% immunization is not necessary (herd immunity)

Blocking vehicle-mediated transmission

• water purification

• effective cooking

• prevention of food contamination with infectious agents

Quarantine

• limiting freedom of movement of individuals carrying infectious agents

• minimum time required for a quarantine period is equal to longest period of communicability (transmissibility) of the disease

Elimination of animal reservoirs

• immunization of animals that act as reservoirs of diseases such as bovine tuberculosis, brucellosis (highly effective when monitored properly)

• eradication of animals that act as reservoirs of diseases such as tularemia, plague, Lyme disease (sometimes effective, difficult to monitor properly)

Industrial vs. "developing" countries

different disease patterns are found in different countries because of varying lifestyles and levels of poverty (which relates to poor community health infrastructure and medical treatment)

Travel to endemic areas

immunization is helpful when possible and may be required before travel can be initiated