Study Set Content:
the investigator determines through a controlled process the exposure for each individual (clinical trial) or community (community trial), and then tracks the individuals or communities over time to detect the effects of the exposure. For example, in a clinical trial of a new vaccine, the investigator may randomly assign some of the participants to receive the new vaccine, while others receive a placebo shot. The investigator then tracks all participants, observes who gets the disease that the new vaccine is intended to prevent, and compares the two groups (new vaccine vs. placebo) to see whether the vaccine group has a lower rate of disease. Similarly, in a trial to prevent onset of diabetes among high-risk individuals, investigators randomly assigned enrollees to one of three groups — placebo, an anti-diabetes drug, or lifestyle intervention. At the end of the follow-up period, investigators found the lowest incidence of diabetes in the lifestyle intervention group, the next lowest in the anti-diabetic drug group, and the highest in the placebo group
Experimental studies
refers to a disease that is regularly found and consistently present in a particular geographic area or population. It occurs at a stable, predictable rate
endemic
occurs irregularly and infrequently, usually affecting a small number of people at unpredictable times or locations.
Sporadic disease
condition is one that occurs at a consistently higher-than-expected rate within a population, often for a long period.
Hyperendemic
is the occurrence of a disease in excess of normal expectancy within a specific geographic area over a particular time frame
Epidemic
refers to an epidemic that has spread across multiple countries or continents, often affecting a large portion of the population
Pandemic
epidemic occurs when a group of people is exposed to the same infectious agent from a single source, such as contaminated food or water.
Common-source
occurs when an infectious disease spreads from person to person, typically through direct contact or droplets in the air.
Propagated epidemic
as both elements of a common-source and propagated outbreak, where an initial common source is followed by person-to-person spread. Example: A foodborne illness outbreak that later spreads throu
Mixed epidemic
in 541 A.D. was attributed to the bubonic plague and wiped out 25 to 50 million people in one year
The Plague of Justinian
killed more than 75 million people from 1347 to 1351, including those who died in Europe, Middle Eastern lands, China, and India.
Black Plague
pandemic killed well over 50 million people in one year, including 675,000 Americans.
1918 Spanish flu
of the 20th century claimed between 300 and 500 million lives. In 1980, smallpox was declared eradicated due to a massive campaign launched by the World Health Organization (WHO) in 1959. It is the only human disease that has ever been eradicated.
The smallpox pandemic
caused by the SARS-CoV-2 virus claimed nearly 7 million lives worldwide between December 2019 and May 2023.The WHO declared COVID-19 a pandemic on March 11, 2020, prompting shutdowns across the globe. In May 2023, WHO downgraded COVID from a global public health emergency to an ongoing health concern.
The COVID-19 pandemic
continues to kill over 1.5 million people annually. Despite the availability of effective treatment, the bacteria that causes tuberculosis is increasingly resistant to drugs used to treat it
tuberculosis pandemic
has killed over 39 million people since 1982.16 However, with the availability of effective HIV treatment, it is no longer considered a pandemic. It is an epidemic or hyperendemic in specific regions.
HIV pandemic
was an outbreak of H1N1 influenza in the United States in 2009. Over 60 million Americans were affected, resulting in 274,304 hospitalizations and 12,469 deaths
swine flu pandemic
include rates and proportions used to quantify how often a disease occurs in a population. These include incidence and prevalence, and they allow epidemiologists to describe the burden of disease
Frequency Measures
A measure of () provides a single value that summarizes an entire distribution of data
Central location
Measures compare one part of the distribution to another part of the distribution, or the entire distribution
Frequency
