Timely and robust type-based enterovirus (EV) and parechovirus (PeV) surveillance has the potential to inform disease prevention strategies by supporting the recognition of outbreaks and guiding the development of diagnostic tests and interventions, according to the recently published Morbidity and Mortality Weekly Report.

Infections caused by members of the Picronaviridae family (EV and PeV) are associated with various clinical manifestations and can result in death. The genus Enterovirus includes 4 species of enterovirus (A-D) known to infect humans, and the genus Parechovirus includes 1 species (A) that infects humans.

During 2014 to 2016, a total of 2967 cases of EV and PeV infection were reported to the National Enterovirus Surveillance System (NESS) in the United States, with the largest number of reports in 2014 (68%), when a large nationwide outbreak of enterovirus D68 (EV-D68) occurred.

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Reports to the National Respiratory and Enteric Virus Surveillance System during 2014 to 2016 indicated that circulation of EV peaks annually in the summer and early fall. Because the predominant types of EV and PeV vary from year to year, tracking these trends requires consistent and complete reports from laboratories with the capacity to perform typing.

The objectives of type-based EV and PeV surveillance are to help public health practitioners determine long-term patterns of circulation for individual types, interpret trends, support recognition of disease outbreaks associated with circulating types, guide the development of new diagnostic tests and therapies, and monitor detections of poliovirus. NESS is a passive, laboratory-based surveillance system that has been used to track EV and PeV report and is the most comprehensive database of these reports in the United States. National Respiratory and Enteric Virus Surveillance System is also a passive laboratory-based surveillance system that collects testing data for untyped EV and aggregates reports of tests for EV and the percentage of positive tests by week.

A total of 2967 EV and PeV cases were reported to NESS in 2014 to 2016, which included 2758 (93.0%) for which the type was unknown. Of the 2758 cases, 99.7% included 1 virus type and 0.3% included 2 virus types. Of the patients in whom sex was known, 60.0% were male, and of the patients in whom age was known, the median age was 4 years. California was the most frequently reported state of residence (15.1%), followed by New York (13.4%).

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Furthermore, EV-D68 was the most frequently reported type during 2014 to 2016, accounting for 55.9% of reports for this period, including 68.0% in 2014 when the large outbreak occurred. After EV-D68, the most frequently reported types during 2014 to 2016 were echovirus 30 (13.1% of reports of non-EV-D68 types), coxsackievirus-A6 (12.5%), echovirus 18 (9.5%), and coxsackievirus -B3 (9.0%).

Data reported to NRVESS were used to evaluate trends in the percentage of positive tests for EV over time. Among 62,210 specimens from which virus isolation was attempted, 0.6% tested positive for untyped EV. Furthermore, among 70,915 specimens tested by reverse transcription-polymerase chain reaction, 7.8% were positive. The percentage of specimens testing positive peaked in the summer or early fall for all years.

Overall, study authors conclude that “improved type-based surveillance can inform disease prevention strategies by supporting outbreak detection and guiding the development of new tests and interventions.”


Abedi GR, Watson JT, Nix WA, Oberste MS, Gerber SI. Enterovirus and Parechovirus surveillance – United States, 2014-2016. Morb Mortal Wkly Rep (MMWR). 2018;67(18):515-518.