An outbreak of enterovirus 68


EV-A71 by Jason Roberts

During the winter of 1962 in California, a new virus was isolated from the oropharynx of 4 children who had been hospitalized with respiratory disease that included pneumonia and bronchiolitis. On the basis of its physical, chemical, and biological properties, the virus was classified as an enterovirus in the picornavirus family. Subsequently named enterovirus D68, it has been rarely reported in the United States (there were 79 isolations from 2009-2013). Towards the end of August 2014, an outbreak of severe respiratory disease associated with EV-D68 emerged in Kansas and Illinois.

Hospitals in Kansas City, Missouri, and Chicago, Illinois reported to the CDC an increase in the number of patients hospitalized with severe respiratory illness. EV-D68 was subsequently identified by polymerase chain reaction and nucleotide sequencing in 19/22 and 11/14 nasopharyngeal specimens from Kansas City and Chicago, respectively. Median ages of the patients were 4 and 5 years in the two cities, and most were admitted to the pediatric intensive care units due to respiratory distress. Other states have reported increases in cases of severe respiratory illness, and these are being investigated at CDC to determine if they are also associated with EV-D68.

There is no vaccine to prevent EV-D68 infection, nor is antiviral therapy available to treat infected patients. Current treatment is supportive to assist breathing; in a healthy individual the infection will resolve within a week. In the current outbreak no fatalities have been reported.

EV-D68 has been previously associated with mild to severe respiratory illness and is known to cause clusters of infections. It is not clear why there has been a sudden increase in the number of cases in the US. According to Mark Pallansch, Director of the Division of Viral Diseases at CDC, “our ability to find and detect the virus has improved to the point where we may now be recognizing more frequently what has always occurred in the past. So a lot of these techniques are now being applied more routinely both at the CDC but also at state health departments.” (Source: NPR).

I am sure that the nucleotide sequence of the EV-D68 virus isolated from these patients will reveal differences with previous strains. However whether or not those changes have anything to do with the increased number of isolations in the US will be very difficult to determine, especially as there is no animal model for EV-D68 respiratory disease.

Although how EV-D68 is transmitted has not been well studied, the virus can be detected in respiratory secretions (saliva, nasal mucus, sputum) and is therefore likely to spread from person to person by coughing, sneezing, or touching contaminated surfaces. The virus has been isolated from some of the children in California with acute flaccid paralysis, and there is at least one report of its association with central nervous system disease. In this case viral nucleic acids were detected in the cerebrospinal fluid. EV-D68 probably does not replicate in the human intestinal tract because the virus is inactivated by low pH.

Readers might wonder why a virus that causes respiratory illness is called an enterovirus. This nomenclature is largely historical: poliovirus, which replicates in the enteric tract, was the prototype member of this genus. Other viruses, including Coxsackieviruses and echoviruses, were added to the genus based on their physical and chemical properties. However soon it became apparent that many of these viruses could also replicate in the respiratory tract. Years later the rhinoviruses, which do not replicate in the enteric tract, were added to the enterovirus genus based on nucleotide sequence comparisons. While it was decided to keep the name ‘enterovirus’ for this group of viruses, it is certainly confusing and I would argue that it should be replaced by a more descriptive name.

Comments on this entry are closed.

  • Casey Finnerty

    Thanks for the great summary. I saw some doctors quoted in the popular press as saying there were no tests for the virus. Wouldn’t it be more correct to say that a test (a Luminex RT-PCR assay) is available, but cannot distinguish among most enteroviruses without follow up sequencing? Would there be a set of primer sequences we could use to differentiate strains using RT-PCR and melt curve analysis without sequencing?

    (This was first posted to Google+.) Sorry for the cross-posting.

  • Correct, the current test uses PCR with pan-enterovirus primers, followed by sequencing to determine the genotype. A melt curve analysis as you suggest should work as well.

  • CRS_DrPH

    “Readers might wonder why a virus that causes respiratory illness is called an enterovirus.” Thanks for the explanation, I was one of the epidemiology community who was confused by the nomenclature! Indeed, it seems like it is time to clean up the convention on naming these things!

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  • Randall

    U.S. prez recently signed an executive order, expansion of existing order to allow the authorities to take a person who shows respiratory problems or who shows no signs of illness at all. look it up

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  • Kelly Maxwell

    The assistant superintendent of the Hamilton Township (Mercer County) School Ditrict sent a Township-wide telephone message to parents this morning (10/4) announcing that a 4-year-old child died from a respiratory illness last week. The CDC confirmed this week that the child was infected with EV-D68.

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  • Brian

    I’m not a doctor or scientist and I ask this question out of sheer ignorance. While reading about the measles vaccine debate, I noticed on some Web pages and blogs in the “other stories you may be interested in” section, stories about ev68 and the possible paralysis it MAY be causing or related to. One article mentioned that most kids who had both conditions had been fully immunized. Then I read that ev68 was discovered – for lack of a better term- in 1962 and the measles vaccine in 1963. Any chance over immunized children are more apt at getting the ev68? Could one have to do with the other?