Nonpolio Enterovirus and Human Parechovirus Surveillance — United States, 2006–2008

GR Villarruel, MPH; GE Langley, MD; MS Oberste, PhD; M Pallansch, PhD


Morbidity and Mortality Weekly Report. 2010;59(48):1577-1580. 

In This Article

Abstract and Introduction


Enteroviruses, members of the Picornaviridae family, are common viruses associated with clinical manifestations ranging from mild respiratory symptoms to serious conditions, including aseptic meningitis, encephalitis, neonatal sepsis, and acute flaccid paralysis. Approximately 100 serotypes of nonpolio enteroviruses have been recognized,[1] and some viruses previously classified as enteroviruses, namely echovirus 22 and 23, recently have been reclassified as human parechoviruses (HPeVs), a different genus within the Picornaviridae family. This report describes trends in nonpolio enterovirus and HPeV detections during 2006–2008, based on data from two laboratory-based surveillance systems, the National Enterovirus Surveillance System (NESS) and, for the first time, the National Respiratory and Enteric Virus Surveillance System (NREVSS). As in previous years, approximately 70% of detections occurred during July–October, the peak enterovirus season. The five most common enterovirus serotypes (coxsackievirus B1 [CVB1], echovirus 6, echovirus 9, echovirus 18, and coxsackievirus A9) accounted for 54% of total serotyped detections. During 2006–2008, southern states reported the most serotyped enterovirus detections, followed by midwestern states, western states, and the northeastern states. In 2007 and 2008, CVB1 was the predominant serotype detected, accounting for 24% and 19% of overall detections, respectively. In 2007, CVB1 was implicated in an outbreak of serious neonatal infections in the United States.[2] Understanding trends in enterovirus and HPeV circulation can help clinicians decide when to test for these infections. Also, more timely reporting of data could help public health officials recognize outbreaks associated with these viruses.

NESS, initiated in 1961, is a passive, voluntary surveillance system that monitors laboratory detections of enteroviruses in the United States. Participating laboratories are encouraged to report enterovirus detections by serotype, specimen type, collection date, age of patient, and sex of patient to CDC monthly. Enterovirus serotyping is performed by sequencing the genome region encoding the VP1 capsid protein by immunofluorescence using type-specific monoclonal antibodies, or by neutralization with type-specific polyclonal antisera.

NREVSS is a passive, voluntary, laboratory-based surveillance system that tracks temporal and geographic trends in the circulation of respiratory and enteric pathogens. NREVSS began collecting enterovirus reports in July 2007. It collects the number of enterovirus tests and the proportion that are positive, by specimen site and collection date; no serotyping, demographic data, or clinical data are reported. All participating laboratories that reported at least one enterovirus-positive specimen were included in this analysis. Enteroviruses were detected by cell culture or nucleic acid detection (polymerase chain reaction).

During 2006–2008, enterovirus and HPeV detections were reported from 49 states through one or both of these surveillance systems during the years specified (Figure 1). A total of 20 laboratories (including 18 public health laboratories, one private reference laboratory, and CDC's Picornavirus Laboratory) reported results to NESS. Public health and private laboratories without the capacity to serotype send specimens to CDC Picornavirus Laboratory for serotyping. A total of 1,632 enterovirus or HPeV detections were reported to NESS during this period (920 from public health laboratories, 661 from the one reference laboratory, and 51 from CDC's Picornavirus Laboratory). Of these detections, 1,103 (68%) were reported during July–October. The age of patients for whom age was known (1,415 [87%]) ranged from <1 month to 79 years, with a mean age of 9 years and a median age of 2 years. Children aged ≤1 year accounted for 660 (47%) of these 1,415 enterovirus or HPeV detections for which the age of patient was known. Cerebral spinal fluid was the most common source for detections, accounting for 743 (51%) of the 1,468 reports of known specimen type, followed by 324 (22%) detections from throat-nasopharyngeal specimens, 268 (17%) from stool-rectal swabs, and 133 (10%) from tissue specimens.

Figure 1.

Method of reporting enterovirus detections, by state — National Enterovirus Surveillance System (NESS) and National Respiratory and Enteric Virus Surveillance System (NREVSS), United States, 2006–2008

Enterovirus or HPeV serotypes were specified for 1,171 (72%) NESS reports. By region,* southern states had the most serotyped detections reported, accounting for 418 of 1,167 (36%) reports for which state information was provided, followed by 373 (32%) detections from midwestern states, 222 (19%) from western states, and 154 (13%) from northeastern states. The five most common enterovirus serotypes accounted for 54% of total detections with a known serotype in 2006–2008 (Table). Overall, during 2006–2008, CVB1 was the most commonly detected enterovirus identified in 235 (17%) of 1,171 specimens tested (Table). In 2007, CVB1 was detected in 22 mostly southern and western states; two states reported 70 (51%) of 137 detections. In 2008, CVB1 was detected in 10 states; one state reported 15 (34%) of 44 detections. During 2006–2008, three public health laboratories and CDC's Picornavirus Laboratory reported a total of 21 HPeV type 1 (HPeV1) detections. HPeV1 was one of the 15 most common enteroviruses reported during the surveillance period but was detected in <2% of specimens (Table). During the surveillance period, only 14 cases of enterovirus 71 (EV71), a virus that has caused widespread outbreaks of hand, foot, and mouth disease in several Asian countries,[3] were reported to NESS, and it was not included as one of the 15 most common serotypes reported.

During July 2007–December 2008, a total of 3,192 (3%) of the 108,798 reports sent to NREVSS were positive for enterovirus. One hundred laboratories reported testing for enteroviruses to NREVSS. During this period, the highest proportion of detections was reported during July–October (Figure 2). The proportion of enterovirus-positive specimens was similar across regions.

Figure 2.

Percentage of specimens testing positive for enterovirus, by month of report — National Respiratory and Enteric Virus Surveillance System (NREVSS), United States, July 2007–December 2008

* Midwest: Illinois, Indiana, Kansas, Michigan, Minnesota, Missouri, Ohio, and Wisconsin; Northeast: Massachusetts, New Jersey, and New York; South: Florida, Georgia, Kentucky, Louisiana, Maryland, North Carolina, Oklahoma, and Tennessee; West: Alaska, Arizona, California, Colorado, Hawaii, Nevada, New Mexico, Oregon, Utah, and Washington.


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