Epidemiology: Tracking the Patterns

Physician's microscope illustration by L. Schrauer, 1878

Epidemiologists piece together how diseases are spread, where they come from, and how they can be controlled.  Their work was first described by Hippocrates as the study of what is visited upon people, or diseases that effect a large portion of the population at one time - epidemic diseases. Endemic diseases, on the other hand, are illness that are found in low numbers, such as chicken pox which has been common among elementary school children.

The field of epidemiology has many specialties including:

  • transmission, studying how a disease is spread from person to person;
  • environmental, investigating how environmental exposure affects human health; and
  • disease surveillance, recording how diseases moves throughout a population and making predictions on where diseases will spread.

Disease Surveillance Reports

Disease surveillance reports help physicians and public health officials understand where infectious diseases are located and develop plans to reduce disease spread.  A sampling of disease surveillance reports from the New York State Library Digital Collections includes these federal and NYS documents:

New York State Department of Health Weekly Influenza Surveillance Report

Graph of 2018-2019 positive influenza reports to NYSDOH
NYSDOH weekly influenza surveillance report - May 4, 2019, pg 2

The greatest number flu cases during the 2018-2019 flu season were in late January.

Graph of 2015-2016 positive influenza results reported to NYSDOH
NYSDOH weekly influenza surveillance report - May 7, 2016, pg 2

During the 2015-16 flu season, the greatest number of cases of the flu were in mid-March.

Reports to individual institutions, such as this report to the University of Utah School of Medicine in Salt Lake City, Utah, help public health practitioners learn how to prevent disease spread in their facilities.

Testimonies to elected officials help them with policy decisions and reflect the effectiveness of previous policy decisions. One example of this reporting is found in the US Senate Committee on Foreign Relations, Subcommittee on Africa and Global Health Policy hearing on the progress of the 2014-15 West African Ebola outbreak.

Livestock disease monitoring - the US Animal and Plant Health Inspection Service (APHIS) monitors the health of livestock in the United States. In 2014-15 they tracked avian influenza (HPAI) in domestic poultry flocks and flocks of wild ducks and geese to determine how far the disease had spread throughout the United States.

Wildlife disease surveillance – in 2007 large numbers of New York's bats were suddenly dying off because of the highly contagious white-nosed syndrome. Wildlife biologists from the New York State Department of Environmental Conservation, along with wildlife biologists from across the northeastern US, began tracking the disease. By 2009 they found that the disease, which is caused by a fungus, had spread to eight states.

Disease surveillance reports, like the ones featured in this exhibit, help public health officials, wildlife biologists, and farmers during disease outbreaks.

Last Updated: June 22, 2020