Enterovirus and Parechovirus Surveillance — United States, 2014–2016

Glen R. Abedi, MPH; John T. Watson, MD; W. Allan Nix; M. Steven Oberste, PhD; Susan I. Gerber, MD


Morbidity and Mortality Weekly Report. 2018;67(18):515-518. 

In This Article


EV and PeV type surveillance in the United States was affected by the 2014 EV-D68 outbreak;[1] this type accounted for 68% of identified types in 2014 and 56% of all reported types during 2014–2016. Increased vigilance and the need for rapid identification of new cases led to a large increase in diagnostic testing for EV and respiratory viruses among patients with respiratory illness during the late summer and autumn months of 2014. The number of reports with known type in 2014 was approximately three times higher than the 594 reports of EV and PeV in 2012, the year during the 2009–2013 period that witnessed the largest number of reports of typed EV and PeV.[2,3]

The objectives of type-based EV and PeV surveillance in the United States are to 1) help public health practitioners determine long-term patterns of circulation for individual types, 2) interpret trends in picornavirus-associated illnesses by associating them with circulating types, 3) support recognition of disease outbreaks associated with circulating types, 4) guide the development of new diagnostic tests and therapies, and 5) monitor detections of poliovirus, which is nationally notifiable in the United States.

Reports to NESS continue to be affected by changes in diagnostic practices. For example, qualitative pan-EV molecular testing has largely replaced traditional cell culture virus isolation techniques in clinical settings because it produces results in a clinically relevant time frame and is more analytically sensitive.[4] However, pan-EV molecular testing does not produce type-level results provided by viral culture, resulting in a lower frequency of reporting to NESS compared with prior decades.[4] A CDC-developed real-time reverse transcription–polymerase chain reaction test for EV-D68 was widely adopted among public health laboratories in 2014. Qualitative pan-PeV testing is not as common as pan-EV testing in clinical laboratories in the United States, and PeV typing, for the most part, is limited to reference laboratories.

The findings in this report are subject to at least four limitations. First, NESS is a passive surveillance system that relies on voluntary reports from laboratories, and EV and PeV infections, except for polio, are not nationally notifiable in the United States. Second, to minimize the reporting burden for participating laboratories, patient-level clinical information is not routinely collected, so it is not possible to associate reported types with specific clinical manifestations or severity of illness. Third, typing tends to occur primarily during summer months, which might lead to underreporting of EV and PeV during other times of the year. Finally, although participating laboratories are encouraged to report monthly, reports are often delayed, making the timely compilation of data difficult.

Recent outbreaks, such as those of EV-D68–associated respiratory illness, CV-A6–associated severe hand, foot, and mouth disease, and a cluster of severe PeV-A3 infections among infants,[1,3,5] highlight the continuing need for robust EV and PeV type surveillance. The associations between certain EV and PeV types and specific clinical manifestations have been well documented, but the epidemiology and associated clinical syndromes of many other EV and PeV types remain poorly characterized. Timely and robust type-based EV and 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. To do so would require improved maintenance and modernization of typing capacity within laboratories, timely and consistent reports from participating laboratories, and an increase in the number of reporting laboratories.