and Strebel, 1994). Disease control and surveillance involves not only responding to such reports, but also maintaining vigilance to ensure that appropriate sentinels are in place within an increasingly fragmented health care delivery system.

The primary mechanism for monitoring disease reports is the National Notifiable Disease Surveillance System (NNDSS), maintained by CDC. The list of reportable diseases is determined and revised collaboratively between the Council of State and Territorial Epidemiologists and CDC. Currently, 52 infectious diseases are designated as notifiable (information provided by CDC). CDC operates several additional surveillance systems as well, including a national registry for congenital rubella syndrome and surveillance systems for paralytic polio and diphtheria (Orenstein et al., 1999). CDC also sponsors efforts to collect data beyond the NNDSS for measles, pertussis, tetanus, Haemophilus influenzae type b, and hepatitis B, and relies on laboratory-based surveillance systems to monitor and confirm reports of bacterial meningitis (including Haemophilus influenzae type b and pneumococcal disease). Additional influenza surveillance is performed using a laboratory-based system, as well as death certificate data (Orenstein et al., 1999). Traditionally, influenza surveillance involved monitoring the population through the voluntary reporting of communicable diseases by practicing physicians, with no expectation of complete reporting.

Monitoring of disease reports continues to be one of the primary functions of public health across the nation. Although such efforts can be expensive, they represent an important preventive function that can result in significant health benefits and cost savings for both individuals and communities. For example, a typical case of Lyme disease (which can be prevented by vaccine) diagnosed in the early stages incurs about $174 in direct medical treatment costs. However, delayed diagnosis and treatment can result in complications that cost from $2,228 to $6,724 per patient in direct medical costs in the first year alone (DHHS, 1998). The cost of screening patients who report symptoms is an additional expense borne by those who do not experience the disease itself.

Investigations of disease reports often require independent laboratory confirmation to meet clinical case definitions, as well as epidemiological analysis to trace disease origins, pathways, and high-risk settings. Such investigations commonly involve close and swift data collection and exchange among local, state, and federal employees, who often collaborate to educate and alert the professional science and health communities about important disease patterns.

Public health laboratories have an intrinsic role in these investigations. These laboratories support surveillance activities, conduct outbreak inquiries, and monitor for new or emerging infectious diseases. Public



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