Notice to Readers: Changes in Presentation of Data from the National Notifiable Diseases Surveillance System --- January 13, 2006

The National Notifiable Diseases Surveillance System (NNDSS) monitors and disseminates data voluntarily reported without personal identifiers on notifiable diseases in the United States (1). The system is maintained by CDC, in collaboration with the Council of State and Territorial Epidemiologists (CSTE), which annually recommends additions and deletions to the list of nationally notifiable diseases* and national public health surveillance standard case definitions.^† Case-level data are reported to NNDSS by the 50 states, the District of Columbia, New York City, and five U.S. territories (1).

In collaboration with CSTE and stakeholders (e.g., state health departments), CDC is introducing in this issue of MMWR new formats for presentation of weekly provisional NNDSS data (i.e., Tables I and II) to help health officials monitor data and facilitate detection of local or national trends in diseases. In addition, a new quarterly table, Table IV, will be published for the first time in the April 7, 2006, issue and each quarter thereafter. Figure I and Table III remain unchanged. The process to revise formats for the new tables began in 2003; in June 2004, CSTE approved a position statement regarding the proposed revisions^§ at its annual meeting in Boise, Idaho. In June 2005, CDC provided final drafts of the new formats and an updated implementation plan to all state epidemiologists.

Interpreting weekly incidence data, given surveillance limitations, is complex (2). Provisional data are subject to reporting delays and corrections. Reporting methods differ by state and disease program and are subject to changes in state-specific surveillance policies and procedures. As a result, NNDSS data might not always reflect a true change in the incidence of a disease, but rather a reporting artifact. Despite these limitations, surveillance data can be useful in monitoring disease trends.

The previous Table I (Summary of provisional cases of selected notifiable diseases, United States, cumulative) presented nationwide data on diseases with <300 cases per year or diseases that were notifiable in fewer than 25 states. Incidence was displayed as cumulative year-to-date data for the current and preceding calendar years. The new Table I presents nationwide data on diseases with fewer than 1,000 cases reported during the preceding year.^¶ The table also presents the number of cases during the current week of report, the list of states reporting those cases, the current cumulative year-to-date number of cases, the total cases in the preceding 5 years, and the 5-year weekly average.

The previous Table II (Provisional cases of selected notifiable diseases, United States) presented state and regional incidence for diseases with >300 cases per year or diseases that were notifiable in 25 states or more. Incidence was displayed as cumulative year-to-date data for the current and preceding calendar years. The new Table II presents state and regional data on diseases with >1,000 cases reported during the preceding year.** This new Table II also presents the number of cases during the current week of report, the cumulative year-to-date number of cases for the current and preceding calendar years, and the median and maximum number of weekly cases reported during the preceding 52 weeks.

Quarterly Table IV, to be published for the first time in the April 7 issue, will present data on cases of human immunodeficiency virus (HIV)/acquired immunodeficiency syndrome (AIDS), AIDS, and tuberculosis. These data will be presented only on a quarterly basis because of the limited value of weekly reports to the public health community as a result of differences in reporting patterns for these diseases and because long-term variations in the number of cases are more important than weekly variations. (Pediatric HIV infection data will continue to be updated monthly and displayed in the new Table I). Table IV will present the number of cases for the current quarter, the minimum and maximum quarterly number reported during the preceding 4 quarters, and cumulative year-to-date number of cases for the current and preceding calendar years.

In addition, in the new Table II, three nationally notifiable Enterohemorrhagic Escherichia coli (EHEC) diseases have been replaced by Shiga toxin-producing Escherichia coli (STEC). The number of STEC cases for the current year will be compared with EHEC data from the preceding year.

Finally, NNDSS publication criteria, which are based on information regarding case-confirmation status, have been revised to align more closely with case status criteria in national public health surveillance case definitions. This revision should help make data more comparable across states. The newly revised publication criteria are reflected for the first time in the provisional weekly NNDSS data in this issue of MMWR. The revised publication criteria are posted on the NNDSS website^†† or can be requested by e-mail, [email protected].

References

1. CDC. Summary of notifiable diseases---United States, 2003. MMWR 2005;52(54):1--85.
2. CDC. Update on MMWR Table II: AIDS surveillance data and provisional nationally notifiable disease data. MMWR 2004;53:346.

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Date last reviewed: 1/12/2006