Demographic Differences in Notifiable Infectious Disease Morbidity -- United States, 1992-1994

Before the 1990s, National Notifiable Diseases Surveillance System (NNDSS) data consisted primarily of summary records that lacked demographic information for persons with reported diseases. By 1990, all 50 states were using CDC's National Electronic Telecommunications System for Surveillance (NETSS) to report individual case data that included demographic information (without personal identifiers) about most nationally notifiable diseases. These data are important for evaluating sex-specific differences in the occurrence of infectious diseases; monitoring infectious disease morbidity trends; determining the relative disease burdens among demographically diverse subpopulations in the United States; targeting prevention; and identifying priorities for research and control. This report describes and compares the numbers and rates of cases for the most frequently reported nationally notifiable infectious diseases, by sex and age of persons with reported illness, reported to CDC during 1992-1994. The findings indicate that for seven of the 10 most commonly reported notifiable diseases, the reported incidence is lower among women.

NNDSS data were evaluated for the 48 nationally notifiable infectious diseases * reported to CDC by state, territorial, and local health departments during 1992-1994 (1), the most recent years for which all notifiable disease data were available at the time of this analysis. Data for gonorrhea, primary/secondary syphilis, acquired immunodeficiency syndrome (AIDS), and tuberculosis (TB) were reported to CDC programs with disease-specific responsibility; other NNDSS data were derived from NETSS reports. Reports for persons for whom age or sex was unknown were not included in this analysis. Postcensal estimates from the Bureau of the Census were used to calculate age-specific and sex-specific rates (2). Children were defined as persons aged less than 15 years; adolescents, persons aged 15-19 years; and adults, persons aged greater than or equal to 20 years. Because AIDS cases were reported in a different format, persons with AIDS aged less than 13 years were defined as children and persons aged 13-19 years as adolescents. AIDS cases included in this analysis met the 1993 AIDS case definition for surveillance (3).

During 1992-1994, the 10 most frequently reported nationally notifiable infectious diseases for all ages and both sexes in the United States were, in descending order, gonorrhea, AIDS, salmonellosis, shigellosis, primary and secondary syphilis, TB, hepatitis A, hepatitis B, Lyme disease, and hepatitis C/non-A, non-B. The order remained the same when reports for persons for whom age and sex were unknown were included. Although the incidence of most diseases among children were similar for males and females (Table_1), the reported incidence of gonorrhea for females (29.8 cases per 100,000 population) was more than three times that for males (8.8). For children aged 10-14 years, the reported rate of gonorrhea for females (79.3) was more than four times that for males (19.4). For adolescents, the reported incidence of gonorrhea for females (878.0) was 1.4 times that for males (627.4) (Table_1). For adolescents, there were also sex-specific differences in the incidences of primary and secondary syphilis, hepatitis B, and shigellosis; for all of these diseases, rates for females were approximately twice those for males. For adults, rates were higher among males than females for seven of the 10 most commonly reported notifiable diseases (Table_1).

Reported by: Div of Public Health Surveillance and Informatics (proposed), Epidemiology Program Office, CDC.

Editorial Note

Editorial Note: The findings in this analysis underscore the usefulness of reporting individual case data for evaluation of the differences in major causes of reported morbidity in the United States for both males and females of all ages. Although women use the health-care system more frequently than men (4), for seven of the 10 most commonly reported notifiable diseases the reported incidence is lower among women. Among the three broad age categories, the incidences for salmonellosis (28.2 cases per 100,000 population), shigellosis (25.9), and hepatitis A (13.5) were highest among children. Because hepatitis A virus infection in young children is often asymptomatic, the true incidence of this infectious disease among children may be substantially higher than that based on acute disease surveillance. Among adults, only for salmonellosis and shigellosis were the rates higher for women than for men.

Although most cases of salmonellosis are associated with consumption of contaminated foods of animal origin, some cases are related to environmental contamination (e.g., exposure to pet reptiles {5}). Shigella sp. and hepatitis A are transmitted primarily by the fecal-oral route and are possibly related to poor personal hygiene among persons of all ages and inadequate infection-control measures in the home and workplace. Educating family members and other adults who provide care for children about proper hygiene and infection-control measures can decrease transmission of infectious diseases in the home and other settings (e.g., day care centers) (6). Appropriate use of hepatitis A vaccine in communities with increased hepatitis A rates and among persons at increased risk for infection can prevent hepatitis A (7). To prevent and control foodborne diseases, food handlers (all persons involved in production, preparation, and delivery of food to consumers) should be targeted for education about proper and frequent handwashing, safe storage and preparation of food, and the potential for serious implications (e.g., outbreaks) if food is mishandled (5).

Despite the high incidence of gonorrhea among adolescent and young adult females, surveillance data probably are underestimates because of underreporting. In addition, approximately 50% of gonococcal infections among females are asymptomatic, and other infected females may not seek treatment for the infection. Therefore, appropriate screening of sexually active adolescent and adult females for gonorrhea is important for accurate surveillance as well as for prevention and control of the disease, which if untreated, can result in serious complications (e.g., pelvic inflammatory disease, infertility, and ectopic pregnancy) (8). Hepatitis B also is sexually transmitted among adolescents and adults and is preventable by hepatitis B vaccine (5).

The data in this report include only the reported cases of those diseases designated as nationally notifiable. Factors affecting the representativeness of cases reported to NNDSS include underreporting; delays in reporting; misdiagnosis of disease; and differential patterns of disease detection, disease reporting, and health-care-seeking behavior. The completeness of reporting is strongly influenced by the interests, priorities, and professional and financial resources of national, state, and local officials responsible for disease control and public health surveillance (9). Although certain diseases are not considered nationally reportable, they may be leading causes of morbidity and mortality (e.g., pneumonia and influenza). For example, chlamydia was not included as a nationally notifiable disease until 1995, when it was the most frequently reported notifiable disease (10); more than 1 million cases of chlamydia were reported during 1992-1994.

Analysis of the data in this report by broad age groups may obscure important differences in rates by age for some diseases. For example, the age distribution of persons reported with cases of Lyme disease is bimodal, with the highest reported incidences among children aged 5-9 years and adults aged 45-69 years and substantially lower incidences among older adolescents and young adults.

Because notifiable diseases are underreported and represent only a subset of all infectious diseases, the findings in this report underscore the need for sustained efforts to improve the completeness and consistency of surveillance systems for monitoring the trends of notifiable infectious diseases. Improved understanding of the epidemiology of infectious diseases in subgroups of the U.S. population can assist public health agencies and others in strengthening measures to prevent, monitor, and control the incidence of infectious diseases.

References

1. CDC. National notifiable diseases reporting -- United States, 1994. MMWR 1994;43:800-1.

2. Deardorff KE, Hollmann FW, Montgomery P. PPL-21, US population estimates by age, sex, race, and Hispanic origin: 1990 to 1994. Washington, DC: US Bureau of the Census, Population Division, Population Projections Branch, 1995.

3. CDC. 1993 Revised classification system for HIV infection and expanded surveillance case definition for AIDS among adolescents and adults. MMWR 1992;41(no. RR-17).

4. Horton JA. The women's health data book: a profile of women's health in the United States. Washington, DC: The Jacobs Institute of Women's Health, 1992.

5. Benenson AS, ed. Control of communicable diseases manual. 16th ed. Washington, DC: American Public Health Association, 1995.

6. Thacker SB, Addiss DG, Goodman RA, Holloway BR, Spencer HC. Infectious diseases and injuries in child day care: opportunities for healthier children. JAMA 1992;268:1720-6.

7. CDC. Prevention of hepatitis A through active or passive immunization: recommendations of the Advisory Committee on Immunization Practices. MMWR 1996;45(no. RR-15).

8. CDC. Sexually transmitted disease surveillance 1994. Atlanta, Georgia: US Department of Health and Human Services, Public Health Service, CDC, 1995.

9. Osterholm MT, Guthrie SB, Meriwether RA. Impediments to public health surveillance in the 1990s: the lack of resources and the need for priorities. J Public Health Management Practice 1996;2:11-5.

10. CDC. Ten leading nationally notifiable infectious diseases -- United States, 1995. MMWR 1996;45:883-4.

* Acquired immunodeficiency syndrome; amebiasis; anthrax; aseptic meningitis; botulism; brucellosis; chancroid; cholera; congenital rubella syndrome; diphtheria; primary encephalitis; Escherichia coli O157:H7; gonorrhea; granuloma inguinale; Haemophilus influenzae; hepatitis A; hepatitis B; hepatitis, non-A, non-B; hepatitis, unspecified; legionellosis; leprosy; leptospirosis; Lyme disease; lymphogranuloma venereum; malaria; measles; meningococcal infection; mumps; pertussis; plague; poliomyelitis; psittacosis; rabies, animal; rabies, human; rheumatic fever; Rocky Mountain spotted fever; rubella; salmonellosis; shigellosis; syphilis; syphilis, congenital; tetanus; toxic-shock syndrome; trichinosis; tuberculosis; tularemia; typhoid fever; and yellow fever.

          
TABLE 1. Ten most commonly reported nationally notifiable infectious diseases among                                   
children, adolescents, and adults, * by sex -- United States, 1992-1994 +
================================================================================================================      
                                  Females                                           Males                             
Age group/       --------------------------------------------     --------------------------------------------        
  Rank           Disease                  No. cases    Rate &     Disease                  No. cases    Rate &        
--------------------------------------------------------------------------------------------------------------        
Children                    
 1               Gonorrhea @                24,291     29.8       Salmonellosis              25,457     29.2          
 2               Salmonellosis              22,062     26.6       Shigellosis                22,272     25.6          
 3               Shigellosis                21,520     26.0       Hepatitis A                11,688     13.4          
 4               Hepatitis A                11,247     13.6       Gonorrhea @                 7,477      8.8          
 5               Pertussis                   5,919      7.1       Pertussis                   5,812      6.7          
 6               Congenital syphilis         4,367      5.3       Congenital syphilis         4,552      5.2          
 7               Lyme disease                2,633      3.2       Lyme disease                3,262      3.7          
 8               Tuberculosis                2,539      3.1       Tuberculosis                2,580      3.0          
 9               Meningococcal disease       1,774      2.1       Meningococcal disease       2,209      2.5          
10               Mumps                       1,412      1.7       Mumps                       1,963      2.3          
                            
Adolescents                 
 1               Gonorrhea @               218,018    878.0       Gonorrhea @               164,079    627.4          
 2               Primary/Secondary                                Primary/Secondary                                   
                   syphilis                  5,935     23.4         syphilis                  3,067     11.4          
 3               Hepatitis A                 2,639     10.4       Hepatitis A                 3,019     11.3          
 4               Salmonellosis               2,280      9.0       Salmonellosis               2,531      9.5          
 5               Hepatitis B                 1,812      7.2       Hepatitis B                 1,011      3.8          
 6               Shigellosis                 1,523      6.0       Tuberculosis                  870      3.3          
 7               Tuberculosis                  840      3.3       Shigellosis                   865      3.2          
 8               Lyme disease                  631      2.5       Lyme disease                  717      2.7          
 9               Pertussis                     476      1.9       AIDS @                        683      1.8          
10               AIDS @                        425      1.2       Meningococcal disease         475      1.8          
                            
Adults                      
 1               Gonorrhea @               344,433    122.0       Gonorrhea @               531,384    205.2          
 2               AIDS                       34,872     12.1       AIDS                      187,211     71.0          
 3               Primary/Secondary                                Tuberculosis               46,160     17.5          
                   syphilis                 31,893     11.0              
 4               Salmonellosis              30,286     10.5       Primary/Secondary                                   
                       syphilis                 39,504     15.0          
 5               Tuberculosis               23,184      8.1       Hepatitis A                25,729      9.8          
 6               Hepatitis A                18,258      6.3       Salmonellosis              24,943      9.5          
 7               Shigellosis                14,274      5.0       Hepatitis B                21,640      8.2          
 8               Hepatitis B                13,987      4.9       Lyme disease               10,152      3.9          
 9               Lyme disease               11,024      3.8       Hepatitis C/non-A non-B     9,413      3.6          
10               Hepatitis C/non-A non-B     4,980      1.7       Shigellosis                 8,054      3.1          
--------------------------------------------------------------------------------------------------------------        
* Children were defined as persons aged <15 years; adolescents, aged 15-19 years; and adults,                         
  aged >=20 years. For AIDS cases, children were persons aged <13 years and adolescents were                          
  persons aged 13-19 years. 
+ Persons for whom age was not reported are excluded.                    
& Per 100,000 population.   
@ Data from Georgia were excluded for 1993 because age was not reported and for 1994 because                          
  no cases were reported.   
================================================================================================================      

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