Nonpolio Enterovirus Surveillance -- United States, 1993-1996

Each year in the United States, an estimated 30 million nonpolio enterovirus infections cause aseptic meningitis; hand-foot-and-mouth disease; and nonspecific upper-respiratory disease (1). From January 1993 through December 1996, state public health laboratories reported to CDC virus isolation results for 3209 specimens tested for nonpolio enteroviruses (Table_1). The number of states reporting enterovirus isolations decreased from 25 in 1993 to 14 in 1996. This report summarizes surveillance data for nonpolio enteroviruses and describes temporal trends in nonpolio enterovirus infections during 1993-1996.

During 1993-1996, of the 3209 nonpolio enterovirus isolations reported, echovirus 9 was the predominant serotype reported (12.7%), followed by coxsackievirus B5 (11.5%), echovirus 30 (9.5%), coxsackievirus A9 (6.6%), coxsackievirus B2 (6.2%), echovirus 6 (5.1%), and echovirus 11 (4.5%). None of the 67 known enterovirus serotypes was listed in 3.8% of the reports. Isolates were most frequently obtained from cerebrospinal fluid (25.3%), nasopharyngeal swab (17.6%), and stool (14.1%) specimens.

For the patients from whom enteroviruses were isolated, provisional clinical diagnoses included aseptic meningitis (12.9% of patients), encephalitis (3.7%), pneumonia or respiratory symptoms (3.1%), paralysis (0.03%), and carditis (0.03%). No clinical diagnosis was noted for 72.9% of patients for whom specimens were submitted.

Reported by: State virology laboratory directors. Respiratory and Enterovirus Br, Div of Viral and Rickettsial Diseases, National Center for Infectious Diseases, CDC.

Editorial Note

Editorial Note: To assess temporal trends in enterovirus infections, public health laboratories have voluntarily reported enterovirus isolations by serotype to CDC since 1951. Surveillance data have consistently demonstrated seasonal peaks in enterovirus isolations during summer and early fall (2). Although the predominant enterovirus serotype reported varies each year, certain serotypes are among the most commonly detected each year (1-3). Surveillance data for 1993-1996 are consistent with these previous observations. Excluding the reports with "unknown" serotypes, six serotypes (echovirus 6, 7, 11, and 30, and coxsackievirus A9 and B4) were among the 10 most frequently detected serotypes each year, and echovirus 9 and coxsackievirus B5 were among the 10 most frequently detected serotypes for 3 of the 4 years. During the 4-year period, the 10 most frequently reported serotypes (the above eight serotypes plus coxsackievirus B2 and coxsackievirus B3) accounted for 58.3%-80.8% of isolates each year. Nine of these 10 serotypes also were among the 10 most common serotypes isolated during 1970-1983 -- the period on which the last enterovirus surveillance report was based (2,3). Echovirus 4 was not among the 15 most frequently isolated serotypes reported during 1993-1996; however, it was the fifth most common serotype reported during 1970-1983. Echovirus 7 was the eighth most common serotype isolated during 1993-1996 and the 12th most common serotype isolated during 1970-1983.

The findings in this report are subject to at least two limitations. First, these nationwide aggregated surveillance data are the only information available to describe the major temporal trends in enterovirus infections in the United States; however, these data may not be representative of the general U.S. population. Second, the impact of the decreasing number of laboratories reporting enterovirus isolations to CDC on the capacity to describe temporal trends cannot be determined.

Despite these limitations, these data reemphasize two points about enterovirus infections. First, annual variability in the predominant enterovirus serotypes must be considered in studies of possible links between enterovirus infections and disease. Second, the consistent presence of certain serotypes among the 10 most frequently detected enterovirus serotypes can be used to focus diagnostic activities in virology laboratories.

References

1. Morens DM, Pallansch MA, Moore M. Polioviruses and other enteroviruses. In: Belshe RB, ed. Textbook of human virology. 2nd ed. St. Louis, Missouri: Mosby, 1991:427-97.

2. Strikas RA, Anderson L, Parker RA. Temporal and geographic patterns of isolates of nonpolio enterovirus in the United States, 1970-1983. J Infect Dis 1986;153:346-51.

3. Moore M. Enteroviral disease in the United States, 1970-1979. J Infect Dis 1982;146:103-8.

TABLE 1. Percentage distribution of the 15 most common types of nonpolio enterovirus isolates reported, by year and rank -- United States, 1993-1996
=======================================================================================================================================================
                                     1993                     1994                    1995                    1996                1993-1996
                           ----------------------   ----------------------   ---------------------   ----------------------   -------------------------
Rank                          Virus type        %      Virus type        %     Virus type        %     Virus type         %     Virus type        %
-------------------------------------------------------------------------------------------------------------------------------------------------------
 1                               ECHO 30    25.9%    Coxsackie B2    16.5%         ECHO 9    45.1%   Coxsackie B5     31.6%         ECHO 9    12.7%
 2                          Coxsackie B5     8.5%    Coxsackie B3    10.5%        ECHO 11     6.8%        ECHO 17     10.6%   Coxsackie B5    11.5%
 3                          Coxsackie A9     7.6%         Unknown    10.1%   Coxsackie A9     5.7%         ECHO 6      9.4%        ECHO 30     9.5%
 4                                ECHO 7     5.8%          ECHO 6     7.0%   Coxsackie B2     5.3%   Coxsackie A9      8.6%   Coxsackie A9     6.6%
 5                          Coxsackie B3     4.6%         ECHO 30     5.9%   Coxsackie B5     4.4%   Coxsackie B4      7.7%   Coxsackie B2     6.2%
 6                          Coxsackie B4     3.8%       Entero 71     5.6%        ECHO 30     4.4%        ECHO 11      4.4%         ECHO 6     5.1%
 7                               ECHO 25     3.8%    Coxsackie A9     4.4%         ECHO 7     4.1%         ECHO 7      4.4%        ECHO 11     4.5%
 8                               ECHO 11     3.1%         ECHO 11     3.8%   Coxsackie B4     3.3%        Unknown      3.2%         ECHO 7     4.4%
 9                                ECHO 6     2.7%          ECHO 7     3.3%        ECHO 25     1.9%        ECHO 22      3.2%   Coxsackie B4     4.4%
10                               ECHO 22     1.8%          ECHO 9     2.8%        Unknown     1.6%         ECHO 9      2.4%   Coxsackie B3     4.0%
11                          Coxsackie B2     1.8%    Coxsackie B4     2.8%         ECHO 6     1.2%        ECHO 30      1.8%        Unknown     3.8%
12                             Entero 71     0.7%         ECHO 25     2.8%        ECHO 22     1.1%        ECHO 25      1.5%        ECHO 17     2.7%
13                                ECHO 9     0.7%         ECHO 22     2.8%      Entero 71     0.6%      Entero 71      1.5%        ECHO 25     2.5%
14                               Unknown     0.1%    Coxsackie B5     1.5%   Coxsackie B3     0.4%   Coxsackie B2      1.2%        ECHO 22     2.2%
15                               ECHO 17     0.1%         ECHO 17        0        ECHO 17        0   Coxsackie B3      0.3%      Entero 71     2.1%

Total number  of isolates                    1357                      612                     901                      339                    3209
=======================================================================================================================================================

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