Enterovirus 68 pathophysiology
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
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Overview
Pathophysiology
The clinical manifestation of EV68 infection is not well defined. A number of cases of EV68 infection with pulmonary involvement have been identified in different parts of the world. The clinical signs and symptoms of EV68 range from a mild illness to more severe complications requiring hospitalization and in rare cases leading to death. Major symptoms associated with enterovirus infection include pharyngeal congestion, headache, myalgia, chills, and sore throat but not increased respiratory rate or difficulty breathing. In a few cases associated EV68 infection, respiratory difficulty was noted. Most symptomatic cases were among the younger age groups. The possible role of EV68 in polio like flaccid paralysis requires further research.
EV68 rearranged itself in the spacer region of 5' UTR between the IRES and polyprotein ORF. All the EVD68 strains that were examined after that rearrangement had a 24 nucleotide deletion. In the 1990's, a large change in the virus lead to its division into subgroups A to C. The subgroup C underwent more changes and resulted in 11 nucleotides deletion in the spacer region. This spacer change has lead to a very high impact on the initiation of translation. A variation in IRES is believed to affect the virulence.
Life Cycle
Enterovirus 68 is acid labile and prefers a lower temperature similar to rhinovirus 87, whereas other enteroviruses are more acid stable and can survive at higher temperatures. In a study on the effect of acidity and temperature on viral growth, 5 clinical isolates were tested for acid stability as compared to EV68 FERMON strain. 10 folds serial dilutions of viral samples were inoculated onto 96 culture plates. They were then incubated at a temperature of 33 or 37° C, in an atmosphere of 5% CO2. They were then observed for 7 days for any cytopathic effects. All strains exhibited a 100 to 1000 fold reduction in the infectivity titres following the incubation for 1 hour in pH 3 buffer. In addition, each of EV68 strains grew to a lower titer at 37 °C than at 33 °C.[1][2] It is due to this survivability at lower temperatures and higher pH that most strains are isolated from respiratory specimens. Classically enteroviruses have a predominance of occurrence in summer-fall season and outbreaks occur in cycles spaced out by several years. EV68 also shows a similar seasonal distribution, with most cases occurring within and sometimes in the later part of the typical enterovirus season.[3]
References
- ↑ Oberste, MS.; Maher, K.; Schnurr, D.; Flemister, MR.; Lovchik, JC.; Peters, H.; Sessions, W.; Kirk, C.; Chatterjee, N. (2004). "Enterovirus 68 is associated with respiratory illness and shares biological features with both the enteroviruses and the rhinoviruses". J Gen Virol. 85 (Pt 9): 2577–84. doi:10.1099/vir.0.79925-0. PMID 15302951. Unknown parameter
|month=ignored (help) - ↑ Blomqvist, S.; Savolainen, C.; Råman, L.; Roivainen, M.; Hovi, T. (2002). "Human rhinovirus 87 and enterovirus 68 represent a unique serotype with rhinovirus and enterovirus features". J Clin Microbiol. 40 (11): 4218–23. PMID 12409401. Unknown parameter
|month=ignored (help) - ↑ "Clusters of acute respiratory illness associated with human enterovirus 68--Asia, Europe, and United States, 2008-2010". MMWR Morb Mortal Wkly Rep. 60 (38): 1301–4. 2011. PMID 21956405. Unknown parameter
|month=ignored (help)