Go to full issue: DCN, August/September 2002: Volume 30, Number 5
Assessment is a core public health function, and surveillance for communicable diseases is one type of assessment activity that is continuous over time. Epidemiologic surveillance is the systematic collection, analysis, and dissemination of health data for the planning, implementation, and evaluation of public health programs. The Minnesota Department of Health (MDH) collects disease surveillance information on certain communicable diseases for the purposes of determining disease impact, assessing trends in disease occurrence, characterizing affected populations, prioritizing disease control efforts, and evaluating disease prevention strategies. In addition, prompt surveillance reports allow outbreaks to be recognized in a timely fashion, when control measures are likely to be most effective in preventing additional cases.
In Minnesota, communicable disease reporting is a centralized system, whereby reporting sources submit standardized report forms to MDH. These reports are monitored daily by disease-specific program staff. Cases of disease are reported pursuant to Minnesota Rules Governing Communicable Diseases (MN Rules 4605.7000 - 4605.7800). The Commissioner of Health has determined that the diseases listed in Table 1 must be reported to MDH. As stated in these rules, physicians, health care facilities, medical laboratories, veterinarians, and veterinary medical laboratories are required to report these diseases. These reporting sources may designate an individual within an institution to perform routine reporting duties (e.g., an infection control practitioner for a hospital). Data maintained by MDH are private and protected under the Minnesota Government Data Practices Act (Section 13.38).
Since April 1995, MDH has been participating as one of the Emerging Infections Program (EIP) sites funded by the Centers for Disease Control and Prevention (CDC) and, through this program, has implemented active hospital- and laboratory-based surveillance for several conditions, including selected invasive bacterial diseases and food-borne diseases. Isolates for pathogens associated with these and certain other diseases are required to be submitted to MDH (Table 1).
The MDH Public Health Laboratory performs state-of-the-art microbiologic evaluation of isolates, such as pulsed-field gel electrophoresis (PFGE), to determine whether isolates of selected pathogens (e.g., enteric pathogens such as Salmonella and Escherichia coli O157:H7, and invasive pathogens such as Neisseria meningitidis) are related and therefore may be associated with a common source. In addition, testing of submitted isolates allows detection and monitoring of antimicrobial resistance, which continues to be an increasing problem with many pathogens.
Table 2 summarizes the number of cases of selected communicable diseases reported to MDH during 2001 by district of the patient's residence. Pertinent observations for some of these diseases are discussed below. A summary of influenza surveillance data also is included. However, these data do not appear in Table 2 because the influenza surveillance system is based on reported outbreaks rather than individual cases; and the influenza data reported here pertain to the 2001-2002 influenza season, rather than the 2001 calendar year.
Incidence rates in this report were calculated using disease-specific numerator data collected by MDH and a standardized set of denominator data used by the MDH Infectious Disease Epidemiology, Prevention, and Control Division for the purpose of maximizing the comparability of disease-specific morbidity and mortality rates reported by various programs throughout the division. In particular, changes in the collection of information on race in the U.S. Census 2000 require some estimations of race-specific population sizes in order to calculate the disease-specific incidence rates presented in this report. Population counts by place of residence, age, gender, and race/ethnicity were obtained from the U.S. Census Bureau for 1990 and 2000. Population counts for 1991 through 1999 were estimated by interpolation between the 1990 and 2000 census data. For 2000 census data, population counts by race include the numbers of persons by race alone, or in combination with one or more races. Thus, persons who identified themselves by more than one race are "overcounted."