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Lesson 5: Public Health Surveillance

Section 6: Disseminating Data and Interpretations

"Development of a reasonably effective primary surveillance system took time. Usually, 2 full years were required. Experience showed that development was best achieved by establishing for each administrative unit of perhaps 2–5 million population, a surveillance team of perhaps two to four persons with transport. Each team, in addition to its other duties in outbreak containment, visited each reporting unit regularly to explain and discuss the program, to distribute forms (and often vaccine), and to check on those who were delinquent in reporting. Regularly distributed surveillance reports also helped to motivate these units. Undoubtedly, the greatest stimulus to reporting was the prompt visit of the surveillance team for outbreak investigations and control whenever cases were reported. This simple, obvious, and direct indication that the routine weekly reports were actually seen and were a cause for public health action did more, I am sure, than the multitude of government directives which were issued." [Emphasis added]( 25 )

As Langmuir(2) emphasized, the timely, regular dissemination of basic data and their interpretations is a critical component of surveillance. Data and interpretations should be sent to those who provided reports or other data (e.g., health-care providers and laboratory directors). They should also be sent to those who use them for planning or managing control programs, administrative purposes, or other health-related decision-making.

Dissemination of surveillance information can take different forms. Perhaps the most common is a surveillance report or summary, which serves two purposes: to inform and to motivate. Information on the occurrence of health problems by time, place, and person informs local physicians about their risk for their encountering the problem among their patients. Other useful information accompanying surveillance data might include prevention and control strategies and summaries of investigations or other studies of the health problem. A report should be prepared on a regular basis and distributed by mail or e-mail and posted on the health department's Internet or intranet site, as appropriate. Increasingly, surveillance data are available in a form that can be queried by the general public on health departments' Internet sites.(24)

A surveillance report can also be a strong motivational factor in that it demonstrates that the health department actually looks at the case reports that are submitted and acts on those reports. Such efforts are important in maintaining a spirit of collaboration among the public health and medical communities, which in turn, improves the reporting of diseases to health authorities.

State and local health departments often publish a weekly or monthly newsletter that is distributed to the local medical and public health community. These newsletters usually provide tables of current surveillance data (e.g., the number of cases of disease identified since the last report for each disease and geographic area under surveillance), the number of cases previously identified (for comparison with current numbers), and other relevant information. They also usually contain information of current interest about the prevention, diagnosis, and treatment of selected diseases and summarize current or recently completed epidemiologic investigations.

At the national level, CDC provides similar information through the MMWR, MMWR Annual Summary of Notifiable Diseases, MMWR Surveillance Summaries, and individual surveillance reports published either by CDC or in peer-reviewed public health and medical journals.

When faced with a health problem of immediate public concern, whether it is a rapid increase in the number of heroin-related deaths in a city or the appearance of a new disease (e.g., AIDS in the early 1980s or West Nile Virus in the United States in 1999), a health department might need to disseminate information more quickly and to a wider audience than is possible with routine reports, summaries, or newsletters. Following the appearance of West Nile Virus in New York City in late August 1999, the following measures were taken:

"Emergency telephone hotlines were established in New York City on September 3 and in Westchester County on September 21 to address public inquiries about the encephalitis outbreak and pesticide application. As of September 28, approximately 130,000 calls [had] been received by the New York City hotline and 12,000 by the WCDH [Westchester County Health Department] hotline. Approximately 300,000 cans of DEET-based mosquito repellant were distributed citywide through local firehouses, and 750,000 public health leaflets were distributed with information about personal protection against mosquito bites. Recurring public messages were announced on radio, television, on the New York City and WCDH World-Wide Web sites, and in newspapers, urging personal protection against mosquito bites, including limiting outdoor activity during peak hours of mosquito activity, wearing long-sleeved shirts and long pants, using DEET-based insect repellents, and eliminating any potential mosquito breeding niches. Spraying schedules also were publicized with recommendations for persons to remain indoors while spraying occurred to reduce pesticide exposure." (26)

Depending on the circumstances, reports of surveillance data and their interpretation might also be directed at the general public, particularly when a need exists for a public response to a particular problem.

Pencil graphic Exercise 5.5

You have recently been hired by a state health department to direct surveillance activities for notifiable diseases, among other tasks. All notifiable disease surveillance data are entered and stored in computer files at the state and transmitted to CDC once each week. CDC publishes these data for all states in the MMWR each week, but health department staff do not routinely review these data in the MMWR. The state has never generated its own set of tables for analysis and dissemination, and you believe that it would be valuable to do so to educate and increase interest among health department staff.

  1. What three tables might you want to generate by computer each week for use by health department staff?
  2. You next decide that it would be a good idea to share these data with health-care providers, as well. What tables or figures might you generate for distribution to health-care providers, and how frequently would you distribute them?

Check your answer.

Pencil graphic Exercise 5.6

Last week, the state public health laboratory diagnosed rabies among four raccoons that had been captured in a wooded residential neighborhood. This information will be duly reported in the tables of the monthly state health department newsletter. Who needs to know this information?

Check your answer.

References (This Section)

  1. Langmuir AD. The surveillance of communicable diseases of national importance. N Engl J Med 1963;268:182–92.
  1. Friedman DJ, Parrish RG. Characteristics, desired functionalities, and datasets of state webbased data query systems. J Public Health Management Practice 2006;12(2):119–129. In press.
  2. Henderson DA. Surveillance of smallpox. Int J Epidemiol 1976;5(1):19-28.
  3. Centers for Disease Control and Prevention. Outbreak of West Nile-Like Viral Encephalitis — New York, 1999. MMWR 1999;48(38):845–9.