Rishi Desai, MD, MPH

Modes of infectious disease transmission

NOTES NOTES  COMMUNITY HEALTH DYNAMICS OF OUTBREAKS  ▪ Outbreak: sudden increase in disease occurrence in a speciﬁc time, place, population (e.g. outbreaks of foodbornerelated norovirus acute gastroenteritis)  ▪ Infective outbreaks depend on causative pathogen characteristics (such as mode of transmission)  MODES OF INFECTIOUS DISEASE TRANSMISSION osms.it/transmission TRANSMISSION  ▪ The passing of a pathogen-causing communicable disease from an infected host to another individual/group  MODES OF TRANSMISSION  ▪ Depends on responsible organism’s characteristics  Direct ▪ Interpersonal contact → infected individuals spread disease ▫ One-to-one (e.g. venereal infection with sexual intercourse) ▫ One-to-multiple (e.g. inﬂuenza with a violent sneeze in a crowded environment) Indirect ▪ Common vehicle (e.g. contaminated air, water/food supply, needle-sharing) ▪ Vectors (e.g. mosquito/tick)  OUTBREAK INVESTIGATIONS osms.it/outbreak-investigations CHARACTERISTICS OF AN OUTBREAK  ▪ Explosive: in epidemic curve, there is a fast, abrupt rise in number of cases, followed by fast, abrupt fall ▪ Indirect transmission: infection limited to individuals who share common exposure  52  OSMOSIS.ORG  ▪ Direct transmission: often impossible to associate new cases to primary case (ﬁrst symptomatic case occurring in deﬁned setting)   

Bias in interpreting results of clinical studies

Bias in performing clinical studies

Confounding

Disease causality

Information bias

Interaction

Selection bias

Causation, validity, and bias

Attributable risk (AR)

DALY and QALY

Direct standardization

Incidence and prevalence

Indirect standardization

Mortality rates and case-fatality

Odds ratio

Relative and absolute risk

Epidemiological measurements

Positive and negative predictive value

Sensitivity and specificity

Test precision and accuracy

Evaluation of diagnostic tests

Disease surveillance

Outbreak investigations

Prevention

Vaccination and herd immunity

Public health

Case-control study

Clinical trials

Cohort study

Cross sectional study

Ecologic study

Placebo effect and masking

Randomized control trial

Sample size

Study designs

Study design

Epidemiology

Modes of infectious disease transmission

Videos

Notes