BCCDC study shows 8-fold increase of Enterovirus D68 in 2014

A study released by the BC Centre Disease Control (BCCDC) shows an 8-fold increase in Enterovirus D68 (EV-D68) detections from October to December 2014, compared to the same period in 2013.

The study, published in the scientific journal EuroSurveillance, is one of the first to look at both community and hospital cases of EV-D68 during the 2014 outbreak in North America. The study describes the EV-D68 epidemic activity in Canada during the fall of 2014, during which over 200 cases were detected in British Columbia alone. EV-D68 is a respiratory virus that causes mild to severe illness, with symptoms ranging from runny nose, sneezing and coughing to wheezing and difficulty breathing. Children with a history of asthma or wheezing are at higher risk for serious complications.

The EV-D68 strain that circulated in BC during the fall of 2014 was found to be similar to other strains globally, including those that caused the 2014 outbreak in the US.

Two surveillance systems were used to learn about patient risk for EV-D68: community-based testing of patients with symptoms similar to influenza-like illness in three provinces (BC, Alberta and Quebec), and the testing of patients who were admitted to hospital with severe respiratory illness in BC.

"Most other studies to date have been based on local hospital clusters involving children and that has limited our view of the full spectrum of illness and age groups affected," says Dr. Danuta Skowronski, Physician Epidemiologist at BCCDC and lead investigator in this study. "In response to alerts from the United States in 2014, we were able to rapidly mobilize our provincial and national partnerships to assess EV-D68 among both community and hospital patients."

Investigators confirmed and quantified a widespread epidemic during the fall of 2014 and, because monitoring was applied across the entire population of BC, they could calculate and compare the actual incidence of EV-D68 hospitalizations by age.

They found that an equal proportion of children and young adults who sought care from a general practitioner for flu-like illness tested positive for EV-D68, suggesting susceptibility across a wide range of age groups; however, children were hospitalized at a higher rate compared to adults. Children under the age of 10 had a 4 to 5-fold higher rate of hospitalization related to EV-D68 than children between the ages of 10-19, and were hospitalized at rates 15 to 20-fold higher than adults.

"Children and teenagers may suffer more from EV-D68 because they have not been previously exposed to as many kinds of enteroviruses as adults and have not developed immunity to these viruses," says Skowronski. "But higher rates of severe illness detected in children may also be due to closer observation and testing by clinicians when children are affected."

Unique to the 2014 outbreak, five cases of acute flaccid paralysis, a condition defined by neurological symptoms and extreme muscle weakness, were identified in BC, with symptoms persisting more than nine months later. Three deaths were also reported though it remains unclear if EV-D68 infections caused these severe illnesses. The three patients who died all had underlying conditions or co-infections that likely contributed to their cause of death.

The BC provincial laboratory has been continuing to test for EV-D68 in 2015, with no cases found in August or September of this year.

"The frequency of EV-D68 activity has yet to be established," says Skowronski. "There may be several years between cycles so we should continue to monitor for the illness in case of resurgence next year."

Ongoing surveillance in both community and hospital settings is needed in order for investigators to learn more about the disease incidence and potential at-risk groups.

Enterovirus can be spread from person-to-person when an infected person coughs or sneezes. It can also be spread by having close contact, such as touching or shaking hands, with an infected person or by touching contaminated objects or surfaces. There is no specific treatment or vaccine for EV-D68 but simple measures like frequent hand washing and staying home if sick can help prevent the spread of respiratory viruses like EV-D68 or influenza.