intro to infectious disease

what probably killed mozart?
strep throat
what are the 3 outcomes if a microbe infects a host?
host resolves infection, latency (TB, herpes, toxoplasmosis), or death
what does infectious disease result from?
an encounter of a potential pathogen with a susceptible host in conjunction with a suitable portal of entry
what are the “sexy” infectious diseases that garner most of the media attention? how many deaths are they responsible for?
CJD, SARS, Ebola, Anthrax, Smallpox, Monkeypox, West Nile. < 1000 deaths
what are the “killers” in terms of infectious disease? how many deaths are they responsible for? what is the order of the top 3 killers?
TB, HIV, ARI, Diarrhea, Malaria, Rotavirus, Hepatitis, Influenza. > 100,000 deaths. top three are: HIV 3m, TB 2m, Malaria 1m
what does DALY stand for?
diability adjusted life years – a time-based measure that combines years of life lost due to premature mortality and years of life lost due to time lived in states of less than full health
how many DALYs are lost to infectious and parasitic diseases?
445 million total
what is the delicate balance between the host and their microorganism?
as long as the immune system is healthy, the host can fight back against the innoculum/virulence of the pathogen
where do most pathogenic organisms start?
in an animal host
what do organisms that transmit via direct transimission (sexual, kissing, animal bite, transplacental, droplet infection) have minimal ability to survive?
stressful conditions
what is the difference between a droplet nuclei and droplet in terms of disease transmission?
droplet nuclei are <5mm in diameter, eg measles, TB, varicella. droplets are >5mm in diameter, close mucosal contact is needed, (within 2 m) eg SARS, influenza, pertussis, (whooping cough)
what are the modes of transmission of infectious agents?
contact, (direct-body to body or indirect- fomites/environment, HCW’s hands), large droplet, (>5um, travels 3 ft), small droplet, (<5um, airbone), endogenous, (auto-innoculation and device related, common, source and vector borne
what are some examples of ways organisms that transmit indirectly?
vector borne, airborne (aerosol – e.g. TB, measles, chicken pox), vehicle borne, (water, food, blood, tissue, fomite, and surgical instruments). this is an example of adaptation for survival.
what is an example of a reservoir for infectious disease? what growing problem is this related to?
a hospital full of C. difficle colonized patients (most w/noscomial infections), and only a few symptomatic patients with obvious infections (tip of the iceberg). this is related to growing antibiotic resistance.
what is an index case? 1st, 2nd generation case?
and index case would be an unvaccinated pt traveling somewhere and bringing back a disease. 1st and 2nd generation cases would be siblins, schoolmates, and other children in contact who contract the disease
what is isolation?
the process of separating persons known or suspected of being infectious from others, to prevent the spread of disease
what is quarantine?
a compulsory period of isolation/sequestration imposed on a person(s), animal, or thing (exposed but asymptomatic) that might otherwise spread a disease
what might be presenting symptoms of infectious disease?
fever, rash, lymphadenopthy, discharge, (diarrhea, urogenital, eye, etc), cough, mental status change, headache
what is an example of an invasive infection?
candidemia which is a blood borne infection, the 4th leading infection in ICUs, where sterile body fluids become infected. the patient will have to be hospitalized and put on IV antifungal
what does gram staining bacteria help?
it helping determing what kind of antibiotic should be used, ideally narrow spectrum antibiotics should be used
what color are gram positive bacteria?
violet
what color are gram negative bacteria?
red
what are common intra-abdominal pathogens?
gram negatives, followed by anaerobes
what are common skin and soft structure pathogens?
gram positive, (staph/strep/enterococcus)
what do only 40% of physicians comply with?
hand washing, extremely important in patient care. it was pioneered by Ignac Semmelweis who discovered the importance of hand washing in patient care after a study of puerperal sepsis in women giving birth
whose deliveries were done by medical students vs. midwives
what is traditional (long sleeves, neck tie, jewelry) physician attire changing to? why?
sleeves rolled up, gloves, mask, plastic apron, no tie,
no jewelry – to keep disease from spreading
what is the definition of public health?
the art and science of preventing disease, promoting health, and
extending life through the organized efforts of society
what does the “superior doctor” do?
prevents the disease instead of just treating it
what was the first cancer vaccine?
hepatitis B vaccine, causes the hepatocelluar carcinoma
what was the second cancer vaccine?
gardasil/cervarix for HPV which can cause cervical cancer, (men can also be vaccinated)
what has been one of the major public health interventions?
vaccines
what is a public health intervention that has been helpful with HIV?
condoms
what has been a major public health intervention in terms of diarrhael related deaths?
oral rehydration therapy
are insecticides/bed nettings, potable water improvements and TB education public health interventions?
yes
non-infectious diseases such as cancer can be caused by infectious agents?
yes, 16-18% of cancers are caused by infectious agents such as HPV, helicobacter pylori, HBV, EBV, HIV, and helminths.
what causes kaposki’s sarcoma? burkitt’s lymphoma?
HHV-8 causes kaposki’s sarcoma. EBV causes burkitt’s lymphoma
what are some contributing factors to growing antimicrobial/antibiotic resistance?
fear of malpractice suits, patient volume, time and expectations (some doctors find it easier to just write out a prescription), lack of knowledge of natural course of viral disease, diagnostic and prescribing habits, need to return to work, school or day care, release of enormous quantities of antibiotics into agriculture, fisheries, and animal husbandry, inappropriate use, company sponsored symposium (CME)
what are some environments were antbiotic resistance develops?
community hospitals, tertiary hospitals, VA, daycare, feedlots
what is a better way to refer to bronchitis so that pts don’t expect antibiotics they dont need?
“chest cold”
what are internationally notifiable infectious diseases that must be reported to the world health organization for quarantine?
plague, cholera, yellow fever, smallpox, wild type poliovirus, SARS,
novel influenza
where do infectious threats come from?
bioterrorism,new infections emerging, “old” Infections resurging, anti-microbial resistant infections, infections that produced chronic disease
what is norovirus associated with?
cruise ships
what is the highest WHO alert level, when did H1N1 get there?
alert level 6, H1N1 appeared in april, and was at level 6 by june 11
what are the pandemic phases?
1. no new subtype in human 2. circulating animal subtype posing risk to humans 3. human infection with a new subtype 4.small clusters and localized spread 5. large clusters 6.increased and sustained transmission
what was important about the H1N1 pandemic?
it was the first time in history that we have been able to follow a pandemic from the start
what are the essential elements in management of acute respiratory illnesses?
cough ettique, hand-washing, and social distancing
what are “super-spreaders” of SARS?
aerosol and fomites
Antisepsis
the process used to decontaminate the skin of a patient/HCW
Attack rate
proportion of persons at risk who develop symptoms of that disease
Bacteremia
the presence of viable bacteria in the blood
Biofilm
organized communities of (mixed) microorganisms enclosed in a self-produced polymeric matrix attached to an inert or a living surface. Bacteria are difficult to culture in vitro because of their reduced metabolic and divisional rate
Booster effect
antibody levels rise higher after revaccination than they did after initial vaccination.
Carrier
an asymptomatic person who is colonized with a microorganism and has a positive culture
Case Fatality rate
(CFR) the percentage of people diagnosed as having a specific disease who die as a result of that disease
Cluster
a group of two or more cases (with the same subtype) among persons (in different households) sharing at least one meal/food item at an event
Cold chain
the standard recommendations for storage, and transportation of the vaccine, including appropriate equipment
Colonization
presence/multiplication of microorganisms in/on a host in a non-sterile site, without apparent evidence of invasiveness or tissue injury
Contact
a person who may have been exposed to the excreta/secretions of an infected person
Contagious
capable of being spread by contact with sick persons
Contamination
presence of microorganisms on body surface without tissue invasion or presence of microorganisms on inanimate objects.
Control
reduction of disease incidence, prevalence, and morbidity/mortality to a locally accepted level as a result of deliberate efforts requiring continuous intervention
DALYs
to weigh and cumulate the burden imposed by premature death plus years lived with disabilities due to the diseases and conditions considered
Diagnosis
confirming a disease process in symptomatic patients
Disease
(Dis-ease) clinical expression of signs and symptoms
(Dis-ease) clinical expression of signs and symptoms
reduces but does not eliminates, the microbial burden.
Dissemination
invasion of non-contiguous organs secondary to hematogenous spread.
Elimination
can also be defined as reduction in the prevalence of disease to the point at which it ceases to be a public health problem.
Empiric
carefully considered presumptive Rx prior to making the microbiological diagnosis
Endemic
low level frequency of disease at moderately regular intervals, constant presence of a disease/infectious agent in a given geographic area.
low level frequency of disease at moderately regular intervals, constant presence of a disease/infectious agent in a given geographic area.
low level frequency of disease at moderately regular intervals, constant presence of a disease/infectious agent in a given geographic area.
Eradication
reduction of disease incidence to zero (worldwide); intervention efforts are no longer required
Exposure
Contact with a microbe or harboring a microbe w/o clinical evidence of disease (eg anthrax, TB).
Extinction
eradication of the pathogen and the destruction of all laboratory isolates
Fomite
an object that can harbor a pathogenic organism (door knob, diaper changing table, keyboard, stethoscope, thermometer, long necktie)
Food security
access by all members at all times to enough food for an active, healthy life (USDA)
Gold Standard
a relatively irrefutable standard that constitutes recognized and accepted evidence that a certain disease exists
Health
(WHO) a state of complete physical, mental and social well-being and not merely the absence of disease/infirmity.
Health literacy
the degree to which individuals have the capacity to obtain, process, and understand basic health information and services needed to make appropriate health decisions (IOM)
Host
a person/living animal affording subsistence or lodgment to an infectious agent under natural condition.
Incidence
the rate at which people without disease develop disease (number of new cases per year) measures appearance of disease. It is the gold standard for assessing prevention.
Incubation Period
time interval between initial contact with infectious agent (exposure) and first appearance of symptoms
Infection
multiplication of infectious agent in host; clinical, histological or immunological evidence of host injury.
Infectivity
ability of a pathogen to enter, survive and multiply in host.
Invasive
an illness, in which isolation of the organism from a normal sterile site occurs, e.g. CSF, blood, synovial fluid, amniotic/pleural/peritoneal fluid.
Isolation
the process of separating persons known or suspected or being infectious from others, to prevent the spread of disease
Latency
carriership of the pathogen’s genome in a seropositive individual with a primary low-grade, persistent infection, but w/o signs of active replication
Neglected diseases
are those that exhibit a considerable and increasing global burden, and impair the ability of those infected to achieve their full potential, both developmentally and socio-economically
Nosocomial Infection (Health-care associated)
hospital/nursing home-acquired infection after 72 hours of admission.
Opportunist
organism causing disease in a compromised host.
Outbreak
occurrence of two or more symptomatic cases in different households with a common exposure
Pandemic
spread of epidemic among continents
Parasite
an organism living in or on another living organism (a host), which obtains part or all of its organic nutrients from the host, and causes a degree of damage to its host.
Pasteurization
the critical reduction of pathogens in a substance, especially a liquid, at a temperature and for a period of time that destroys objectionable organisms without major chemical alteration of the substance (milk, fruit juice).
Pathogen
microorganism capable of causing disease by its ability to cross epithelial barriers and/or intact cells.
Pathogenesis
changes that occur when the host interacts with the microorganism
Pathogenicity
ability to produce disease.
Pathogenicity islands
novel genes working together to enhance the virulence potential of a species
Prevalence
number of people who have the disease/currently infected (measures existence of disease).
Prevention
action aimed at eradicating, eliminating or minimizing the impact of disease and disability
Probiotic
a preparation of or a product containing viable, defined microorganisms in sufficient numbers, which alter the microflora (by implantation or colonization) exerting beneficial health effects in the host
Prophylactic
antimicrobial Rx from the earliest possible moment to prevent an infection that is common and important enough to justify such a commitment
Quarantine
compulsory period of isolation (sequestration) imposed on a person/s, animal or thing that might otherwise spread a contagious disease
Quorum sensing
cell-to-cell signaling mechanism in which bacteria respond to hormone-like molecules (auto inducers) produced by other growing bacteria of the same species in the same environment.
Recrudescence
a new outbreak after a period of abatement or inactivity
Reinfection
infection with the same organism (genus) but different species
Relapse
infection with the very same organism/pretherapy isolate (genus and spp
Reproductive rate
the extent to which an infectious disease spreads in a population (the average number of susceptible people infected by an index case over his lifetime). To maintain an epidemic, its reproductive rate must be greater than one. Measure of transmissibility of an infection.
Reservoir
source of a microorganism in the environment/host
Resident flora
colonizes deeper skin layers, multiplies in hair follicles (e.g. coagulase negative Staphylococci, Corynebacteria).
Resistance
a relative insensitivity of a microbe to an antimicrobial drug as tested in vitro and compared with other isolates of the same species
a relative insensitivity of a microbe to an antimicrobial drug as tested in vitro and compared with other isolates of the same species
test(s) done on asymptomatic patients to identify those at an increased risk of a disease
Sensitivity
percentage of people with the disease who test positive (inclusion of the infected), “detection rate”.
Septicemia
systemic disease associated with presence and persistence of pathogenic microorganisms or their toxins in the blood
Sequela/e
an after effect of disease or injury, a secondary result.
Specificity
percentage of people without the disease who test negative (exclusion of the noninfected). In other words, the ability to reject the Dx correctly
Sporadic
occasional cases of disease at fairly regular intervals
Sterilization
completely eliminates or destroys all forms of microbial life.
Subclinical infection
reaction between pathogen and host is limited by host’s immune response.
Success
large-scale disease program (national scope), uses cost-effective interventions, has been sustained for >5 years, and has a major health impact.
Surveillance
the continuing scrutiny of all aspects of occurrence and spread of a disease that are pertinent to effective control.
Symptoms
(Greek) “to fall together” or coincide (manifestation of illness)
Therapeutic
treatment based on the presence of established infection
Transient flora
colonizes superficial skin layers for short periods and is usually
acquired by contact with a patient or contaminated environment (e.g. Staph. aureus, gram-negative bacilli, Candida
Triage
sorting, screening and prioritizing victims in a resource-constrained environment.
Vector
a living transmitter of disease (mosquito, tick, fly).
Virulence
(Latin – virulentus “full of poison”) ability of microorganism to produce disease in a given set of circumstances (quantitative measure of pathogenicity). In other words it is the degree of harm imposed on the host.
Zoonosis
diseases and infections which are naturally transmitted between vertebrate animals and man.
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