Disease Surveillance

Surveillance is intriguing; it involves everchanging information and identifying trends based on new disease data.

The purpose of public health surveillance systems in Missouri and nationwide is to detect changes in trends or distribution of diseases so that investigation, prevention, and disease control can be initiated in the community. With this new information, prompt and more effective action can be taken.

Communicable, environmental and occupational diseases are tracked at the local level by the local public health agency and also at the state level by DHSS. Disease-specific information comes from schools, hospitals, physicians, nurses, laboratories and others.

Local agencies have an active system in place where they maintain regular contact with a representative group of local disease reporters who provide information weekly (and when needed, daily) about diseases that are occurring in their communities. This enables the local agency to have a clear picture of the occurrence of disease in their community.

Knowing what to expect in disease occurrence is particularly important when it comes to bioterrorism and emergency response. When there are more reports of a specific disease than would be expected, the agency can begin to investigate why this is happening.

Since there are many disease-causing organisms that could be used by terrorists to cause a large outbreak affecting many people, knowing what is usual is critical. If a community does not know what is usual, it will not know what is unusual. This is the first line of defense in implementing any emergency plan, especially for disease prevention.


   KEY:
   FP = Flaccid Paralysis
   AM = Aseptic Meningitis (persons over
     18 years of age)
   E = Encephalitis (all ages)
   GB = Guillain Barré Syndrome (all ages)
   P = Parkinsonism (all ages)
   CMBI = Confirmed Mosquito-Borne
     Illness


 Note: Chart was not part of original article.
 It was added to this webpage as a sample.

The DHSS uses disease surveillance information to track trends statewide. Based on data collected over many years, DHSS has calculated for every reportable disease a trend line with upper and lower limits. Diseases are monitored weekly (or daily as needed) and any unusual numbers of cases outside of what we know to be the usual occurrence are investigated.

In some instances, one case of a disease is cause for concern. Anthrax would be one example. In other instances, many cases, of salmonella for example, clustered in a community or facility would be cause for concern.

Additionally, information is received daily from approximately 76 "sentinel" sites that provide data on the types of syndromes/illnesses they are seeing in their facilities. Sentinel sites (hospitals, physician practices, schools, large employers) have catchment areas that include communities that see heavy tourism, areas surrounding military installations, major utilities, large population centers or areas otherwise strategically significant to allow early detection of natural and man-made public health threats in time to minimize their impact on public health and even save lives.

Sentinel sites provide data daily on how many people are seen with respiratory illness, influenza-like illness, gastrointestinal illness, unusual bleeding, headaches, rashes, fevers or chemical exposures. Because these symptoms/ illnesses could indicate possible biological, chemical or radiological exposures (potential acts of terrorism), being able to identify whether the number of instances of these symptoms is unusually high and the area where they are occurring is critical to early intervention.

All disease surveillance, whether it is active, passive or sentinel, provides data that local agencies and the department can use to develop a comprehensive picture of what is happening. It is one concrete method of constantly monitoring the health of the public, so an unusual disease is identified quickly or an unusual number of cases of a disease are known quickly.

Timing is everything with diseases - finding them early before many are ill and implementing prevention and control measures to keep others from becoming ill is what surveillance is all about.

Article by Lyn Konstant, Ph.D., Office of Surveillance
Reprinted with author's permission, from the Missouri Department of Health and Senior Service's June 2003 "Public Health Preparedness and Response UPDATE".