Communicable Disease & Epidemiology

Phone: (616) 632-7228
Fax: (616) 632-7085

The Communicable Disease and Epidemiology division at the Kent County Health Department monitors the occurrence of specific diseases on a community-wide basis.

An explanation of the communicable disease and epidemiology functions at the health department would be incomplete without first providing a definition for that which serves as the foundation of this practice, epidemiology and surveillance.


Epidemiology is the study of the distribution and determinants of health-related states or events in specified populations and the application of this study to the control of health problems. To put it more simply, epidemiology is the task of using data to answer questions of:

  • Who is getting sick?
  • What is making people sick? And,
  • How can we use this information to reduce the risk of others getting sick?

Without quality health data, it is very difficult to answer these questions. A surveillance system that serves to collect health data in a complete and timely manner is thus essential to the practice of epidemiology.


Surveillance is the ongoing systematic collection, analysis, and interpretation of outcome-specific data for use in planning, implementation, and evaluation of public health practice.

Data collected in a surveillance system can be used for many purposes, including:

  • To estimate the magnitude of a health problem in a population
  • To understand the natural history of a disease
  • To detect outbreaks or epidemics
  • To document the distribution of a health event
  • To test hypotheses about causes of disease
  • To monitor changes in infectious organisms

Communicable Disease Surveillance

Communicable diseases are those that can be transmitted from person to person (or animal to human) via direct contact with body fluids, ingesting contaminated food or water, inhalation of contaminated air, or the bite of an infected insect. Bacteria, viruses, and parasites are some of the organisms that can cause communicable diseases. Examples of communicable diseases are Hepatitis B, Salmonellosis, Measles, and West Nile Virus.

Preventing and controlling communicable disease is a necessary and critical aspect of assuring community health, and is an affirmative duty of local public health departments. Protecting the public’s health from communicable disease threats requires a proactive public health disease surveillance system, timely epidemiological assessment, and ongoing disease prevention education.

Because community disease surveillance and control is a critical component of disease prevention, the Kent County Health Department monitors the occurrence of specific diseases on a community-wide basis. Physicians, laboratories, and schools all report cases of disease to the Health Department. With this information, we are able to monitor both the incidence (number of new cases) and prevalence (number of existing cases) of disease in Kent County.

The “Big Picture”

In Michigan, the state Public Health Code requires that healthcare providers (physicians, physician assistants, pharmacists, dentists, nurses, veterinarians, etc.) report any of 77 specific diseases and that laboratories report any of 42 specific organisms identified to the local health department. While health care providers are typically concerned with the health of an individual patient, the focus of public health nurses and epidemiologists is on the “big picture” of health in a community.

A single case of a disease may not cause alarm in a physician’s office. However, timely and accurate reporting of communicable disease data allows health department personnel to determine whether this single case may be part of a larger problem in the community. With complete information, health department personnel can check if the disease is related to other cases as part of a cluster or is part of an outbreak (where the number of cases is greater than the number expected during a defined period of time).

Disease Detectives

Public health nurses and epidemiologists act as detectives who try to connect pieces of a puzzle in solving disease mysteries. These public health professionals monitor disease information to determine if there are more cases of a particular disease than expected. In addition, they investigate cases of disease to discover clues that may link the infected individuals and uncover the source of their infection. Once the culprit is discovered, these public health professionals provide education to those who are ill and those at risk of becoming ill to help prevent the spread of infection.

Timely and accurate reporting of communicable disease information thus allows health department personnel to:

  • Quickly identify single or multiple cases of disease occurring within a similar location or time
  • Identify persons at risk of acquiring or transmitting disease
  • Identify care needs and recommend appropriate prevention measures for those affected
  • Provide education for future prevention
  • Assess the effectiveness of public health disease prevention programs

Chronic Disease Surveillance

Chronic diseases cannot be transmitted from person to person. Examples of chronic diseases are heart disease, diabetes, and cancer. Poor health behaviors (lack of physical activity, smoking, poor eating habits, etc.) may increase a person’s risk for chronic disease.

Many of the advances in public health and life expectancy in the United States during the 20th century were a direct result of communicable disease control. Until roughly the 1950s, most Americans died of infectious disease. With these diseases under control and Americans living longer, the major disease burden in the US shifted to chronic diseases. Recently, health issues such as obesity, asthma, and infant mortality have gained a lot of attention in the media and are important issues to address as we strive to achieve a healthier America.