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Acute respiratory illness clusters attributed to human enterovirus 68
Akira Suzuki TI. MMWR. 2011;60:1301-1304.
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Six clusters of respiratory illness-associated human enterovirus 68 have been recently reported in Asia, Europe and the United States. The illness has caused mild to severe infection and three fatalities, according to data published in a recent Morbidity and Mortality Weekly Report.
“Clinicians should be aware of [human enterovirus 68 (HEV68)] as one of many possible causes of viral respiratory disease and should report clusters of unexplained respiratory illness to the appropriate public health agency,” the researchers wrote.
Between 2008 and 2010, six clusters of respiratory illness-associated HEV68 were reported:
- 21 cases that included two fatalities were reported in the Philippines.
- More than 120 cases, including one fatality were reported in Japan; clinical and demographic data were only available on a subset of 11 pediatric patients.
- 24 cases were identified in a prospective, hospital-based study of respiratory infections in the Netherlands.
- Six cases were reported in a hospital in Atlanta.
- 28 cases were reported in a pediatric hospital in Philadelphia.
- A community hospital in Arizona sent seven nasopharyngeal specimens to the CDC; five were identified as HEV68.
HEV68 cases were confirmed by reverse transcription-polymerase chain reaction (RT-PCR) testing in each cluster, followed by partial sequencing of the structural protein genes, VP4-VP2, VP1, the gold standard test for HEV 68 detection, according to the researchers.
The researchers cautioned that some diagnostic tests, such as the CDC rhinovirus real-time RT-PCR assay, may not detect HEV68 or may misidentify the infection as human rhinovirus.
In an accompanying editorial, CDC officials wrote: “Identification of a large number of patients with HEV68 respiratory disease detected during a single season, such as described in this report, is a recent phenomenon. Whether this increase in recognized cases is attributable to improved diagnostics or whether the clusters themselves represent an emergence of the pathogen is unknown.”
For the past few years, it has been realized that many enterovirus infections can also be transmitted through the respiratory route. Thus, the biologic and clinical borders between the enterovirus and the rhinovirus groups are fading, at least in part. HEV68 is peculiar in this regard. In fact, since 2002, it is known that HEV68 shares antigenic properties with the human rhinovirus 87 (HRV87), that these agents are almost genetically identical, that both are acid-sensitive and grow better at temperatures lower than 37·C (characteristics that are proper of rhinoviruses and that probably explain their lack of enteropathogenicity), and that both share the same cellular receptor (DAF). Thus, HEV68 and HRV87 are now held as strains of a single virus type that presents features of both rhinoviruses and enteroviruses. As a consequence, HRV87 has been removed from the rhinovirus group.
The MMWR researchers suggest that it remains unclear ‘whether this increase in recognized HEV68 cases is attributable to improved diagnostics or whether the clusters themselves represent an emergence of the pathogen.’ Studies conducted in Finland indicate that neutralizing antibodies to HEV68 were widely represented in the population in 2002. Thus, in at least some communities, this agent is not new or rare.
The report, in any case, recalls pediatricians and clinicians of the vast and still undefined array of diseases that are possibly associated with the entero/rhinovirus group of agents. This is particularly important, since many of these viruses are responsible for relevant clinical syndromes, and are suspected to produce, in a minority of cases, persistent and severe conditions (eg, dilated myocardiopathy, post-polio syndrome, chronic fatigue syndrome with fibromyalgia). Finally, this work draws attention to the need for specific antipicornaviral drugs. The necessity of these agents has been recently evidenced by the WHO as an essential component of the final steps of the polio eradication campaign. In the mean time, the compassionate use of antivirals under development and/or intravenous immunoglobulin may be of help in critical cases.
Antonio Toniolo, MD
University of Insubria, Varese, Italy
Disclosure: Dr. Toniolo reports no relevant financial disclosures.
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