A new report on enterovirus and parechovirus infections from 2014 to 2016 in the United States is highlighting the need for improved surveillance to detect outbreaks and develop effective interventions.
Non-polio enteroviruses are highly common overall in the United States, causing 10 to 15 million infections each year and tens of thousands of hospitalizations, according to the Centers for Disease Control and Prevention (CDC). There are 4 species of the Enterovirus genus and 1 species in the Parechovirus genus that cause infections in humans. Most individuals who catch a non-polio enterovirus infection, however, do not fall ill or experience only mild symptoms such as fever, runny nose, skin rash, as well as body and muscle aches. More serious illnesses from enterovirus infections can include viral conjunctivitis, respiratory illness, myocarditis, viral meningitis, and hand, foot, and mouth disease. In a recent 2016 study, researchers found that an outbreak of acute flaccid myelitis in a Colorado pediatric hospital was associated with enterovirus D68 (EV-D68) infection. Another recent study noted that cases of human parechovirus in newborns and young infants can lead to severe disease, including sepsis-like illness.
The CDC’s Morbidity and Mortality Weekly Report (MMWR) published on May 11, 2018 included a surveillance report on cases of enterovirus and parechovirus in the United States that occurred from 2014 to 2016. The report covered cases reported to the CDC’s National Enterovirus Surveillance System (NESS), a voluntary system that monitors cases of enteroviruses and parechoviruses detected in participating laboratories. During this time period, NESS had a total of 2,967 cases of enterovirus and parechovirus in the United States, which included cases from the nationwide 2014 outbreak of EV-D68, resulting in severe respiratory illnesses. The outbreak occurred from August 2014 to January 2015 and saw a total of 1,153 cases in 49 states and the District of Columbia, as confirmed by public health laboratories. The majority of those affected were children with a history of asthma or wheezing. Public health officials believe many thousands of additional individuals were also infected but experienced only mild illness and did not seek medical treatment or testing.
Overall, NESS saw 1,984 cases of enteroviruses in 2014, including EV-D68, coxsackieviruses, echoviruses, and parechovirus A3. In 2015, that total dropped to 342 reported cases, and in 2016, there were 308 reported cases. However, the new surveillance report gives an incomplete view on the scope of these infections.
“With the exception of polio, enteroviruses and parechoviruses are not nationally notifiable diseases, so it is not mandatory for laboratories or clinicians to report these cases. Reporting to NESS is voluntary,” explained study author Glen R. Abedi, MPH, of the CDC’s National Center for Immunization and Respiratory Disease, in an interview with Contagion®.
“Diagnostic testing is more likely to be performed on moderately or severely ill individuals who seek medical care. Most people who are infected with non-polio enteroviruses and parechoviruses do not become ill, or they experience very mild illness. These individuals are less likely to see a doctor and, therefore, would not be tested for enterovirus or parechovirus infection,” he added.
In addition, few laboratories have the diagnostic equipment to perform typing for specific viruses, according to Dr. Abedi. In response to the 2014 outbreak of EV-D68, the CDC developed a simpler diagnostic test for the virus and shared it with laboratories across the country. Still, the report notes that outbreaks of EV-D68 and hand, foot, and mouth disease in recent years emphasize the need for more virus type-based surveillance to improve outbreak detection and prevention strategies.