Current Trends
Update: Graphic Method for Presentation
of Notifiable Disease Data -- United States, 1990
Since April 1990, data from the National Notifiable Diseases
Surveillance System for 14 diseases have been published in a
graphic
format in the MMWR (Figure I, page 118) (1). The bar graph compares
provisional reports for a 4-week period with the mean of 15 4-week
totals (from the previous, comparable, and subsequent 4-week
periods for
the last 5 years) (2). Ratios that exceed national historical
limits
(calculated based on two standard deviations of the historical
baseline)
are indicated by striping in the bars. This report summarizes an
evaluation of this new method.
To evaluate the method, state health departments provided
supplemental information for diseases that exceeded historical
limits
during the first 6 months (April-September 1990) of publication of
Figure I. For each interval in which a disease exceeded historical
limits, the excess cases were usually accounted for by increased
reports
received from six or fewer states. The only exception was measles,
which
exceeded historical limits every 4-week period after April 21,
1990;
increased measles activity was reported from most states (3).
Explanations for the increased number of reported cases of a
given
disease were readily available from most state health departments
(Table
1); in some states, increased reports from multiple counties
accounted
for the increase, and no epidemiologic linkage was identified.
Batch
reporting of endemic or epidemic disease was often identified as a
contributing factor in increased reports. For diseases with
relatively
small numbers of cases reported nationally (i.e., pertussis,
legionellosis, and rubella), small increases in reporting caused
totals
to exceed historical limits. Many of the events reported by state
health
departments were small outbreaks; however, when aggregated with
other
nationally reported events, these outbreaks were sufficient to
result in
numbers exceeding historical limits. This method detected one
ongoing
outbreak of substantial public health importance in California;
multiple
outbreaks of rubella, primarily in unvaccinated adults, accounted
for
the increases in reporting (4).
Reported by: CH Woernle, MD, State Epidemiologist, Alabama Dept of
Public Health. L Dales, MD, GW Rutherford, III, MD, State
Epidemiologist, California Dept of Health Svcs. R Hamm, MD, W
Staggs, ML
Fleissner, DrPH, State Epidemiologist, Indiana State Board of
Health. DM
Dwyer, MD, E Israel, MD, State Epidemiologist, Maryland State Dept
of
Health and Mental Hygiene. T Pugliese, A DeMaria, MD, State
Epidemiologist, Massachusetts Dept of Public Health. WN Hall, MD,
MG
Stobierski, DVM, KR Wilcox, Jr, MD, State Epidemiologist, Michigan
Dept
of Public Health. D Schneider, JK Gedrose, MN, State
Epidemiologist,
Montana State Dept of Health and Environmental Sciences. S
Kondracki, DL
Morse, MD, State Epidemiologist, New York State Dept of Health. E
Bell,
A Goodman, MD, City Epidemiologist, New York City Dept of Health.
DR
Tavris, MD, Pennsylvania Dept of Health. DM Simpson, MD, State
Epidemiologist, Texas Dept of Health. Surveillance, Investigations,
and
Research Br, Div of Immunization, Center for Prevention Svcs;
Respiratory Diseases Br, Div of Bacterial and Mycotic Diseases,
Center
for Infectious Diseases; Div of Surveillance and Epidemiology,
Epidemiology Program Office, CDC.
Editorial Note
Editorial Note: Limitations of routine national surveillance data
for
notifiable diseases have been described (5,6). However, follow-up
of the
graphic presentation of weekly surveillance data for 14 nationally
notifiable diseases suggests that ongoing routine analysis of
weekly
provisional reports at the national level may detect changes from
historical patterns that signal the need for public health
intervention.
Although the specificity of this method appears high, its
sensitivity is
unknown.
The method used to produce Figure I is not designed to detect
all
epidemics (2). Use of the previous 5-year average as the baseline
for
comparison may not detect all changes in disease reporting if large
variations in disease case counts occurred during the baseline
period.
For example, the failure of the graphic method to demonstrate an
increase in measles activity for the 4-week periods ending April
7-April
21 was due to increased measles activity during the baseline period
used
for comparison. In addition, outbreaks at the state or local level
may
be obscured when combined with other reports. The extent to which
this
occurred during April-September 1990 is unknown; however,
preliminary
information from a pilot project in progress suggests that the same
analytic approach at the state level may be useful (CDC,
unpublished
data).
References
CDC. Changes in format for presentation of notifiable disease
report
data. MMWR 1990;39:234.
CDC. Proposed changes in format for presentation of notifiable
disease report data. MMWR 1989;38:805-9.
CDC. Measles--United States, 1989 and first 20 weeks 1990. MMWR
1990;39:353-5,361-3.
CDC. Increased incidence of rubella and congenital rubella
syndrome--United States, 1988- 1990. MMWR 1991;40:93-9.
Sacks JJ. Utilization of case definitions and laboratory
reporting in
the surveillance of notifiable communicable diseases in the United
States. Am J Public Health 1985;75:1420-2.
Thacker SB, Berkelman RL. Public health surveillance in the
United
States. Epidemiol Rev 1988;10:164-90.
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