National surveillance for non-polio enteroviruses in Canada: Why is it important?

Abstract

A widespread outbreak of enterovirus D68 (EV-D68) was detected in association with respiratory illness in children across Canada and the United States during the autumn of 2014. The majority of cases were mild, but some were associated with more severe illness requiring hospitalization; some of the cases also had neurological symptoms including paralysis, and three deaths were reported in British Columbia. EV-D68 is one of many enteroviruses that include Coxsackieviruses, echovirusesand polio virus. Other than polio virus, there are no vaccines available for the prevention of enterovirus infections, nor are there any antiviral medications that have been approved for their treatment. More than 46 different serotypes have been identified to be circulating in Canada over the last 25 years. Until 2014, EV-D68 was rare. Routine genotyping surveillance done by Canada's National Microbiology Laboratory (NML) identified only 85 isolates of EV-D68 between 1991 and 2013, while 282 were detected between July and October 2014. The complexity of the epidemiology of these enteroviruses demonstrates the need for genotype surveillance, to detect outbreaks spatially and temporally, to determine their relative incidence and impact on the population, and to investigate evolutionary trends, such as recombination events, that are thought to play an important part in strain variation and emergence of epidemic strains. In particular, it is important to carry out virological testing on unusual cases of paralysis in children, and to genotype and sequence any viruses identified. Submission of specimens (virus cultures, stool, cerebrospinal fluid or respiratory specimens) from any such cases to the National Centre for Enteroviruses at NML is encouraged.

Figure 1. The seasonality of echovirus infections in Canada, from 1990 to 2009^a

^aMonthly data of positive test identifications from the Canadian virus reporting system (11).

Figure 2. Numbers of cases of EV-68 infection identified in Canada by molecular genotyping at the National Microbiology Laboratory, 2004−2014