Thursday, January 29, 2015

Enterovirus D68 Outbreak


Ever wondered of this question? "More and more outbreaks are detected and traced. Most of them are new pathogens that people have barely heard of. Does that mean, new pathogens are evolving, our immune system is weaker, or simply our technological competence has drastically improved". Different people have varied opinion on this. I contest, with ability to sequence anything and everything, we are detecting the one's which weren't before.

One of the recent talk of town in terms of infectious epidemic is an Enterovirus- EV D68, a respiratory pathogen causing paralysis. Enteroviruses are a genus of positive-sense single-stranded RNA viruses. They are sub classified into Poliovirus and Human Enteroviruses A, B, C, and D. They are sub-typed based on their serological profile. The classification is quite challenging since many strains are known to be recombinants between groups. A more molecular approach has been proposed for classification, however hasn't been widely accepted in literature.

The first isolation report of EV D68, is from California in 1962. 4 children suffering from respiratory illness and were diagnosed with a new virus type which was later classified as EV D68. The number of reported cases has been very low, less than 80 in a period of 4 years (2009- 2013). On August 19, 2014 CDC was notified of a sudden increase in case (Link), in Kansas and Illinois reported to the CDC an increase in the number of patients hospitalized with severe respiratory illness by PCR. The age group was a pediatric population (20 months- 15 years). The interesting part was that it was correlated with Acute Flacid Paralysis, a Polio like condition. Nothing much was known about this virus. By a month nearly 700 cases were confirmed in 46 states in the US. By the end of October 2014, a Real Time PCR specific for the virus was used by the CDC to be used as a lab test. By Jan 15, 2015 CDC has confirmed a total of 1,153 people in 49 states.

An article published in 2012 by Lipkin et al; analyzed multiple isolates genome and gathered that there is emergence of new mutants from a variety of geographical regions. Thus it wouldn't surprise me to see that we are seeing a lot of cases. However, so little is known of its biology. A recent article in Nature News titled "Mystery childhood paralysis stumps researchers", highlights the current effort in understanding the sudden increase in cases. The article highlights that there is neither a vaccine nor a approved specific treatment. Further, it is not known, as to how the virus causes flacid paralysis if at all it does. The evidences are quite circumstantial.

Perhaps its too early to speculate. Just as papers began flooding with Ebola outbreak, I expect a lot of literature to shoot in for EV D68, in near days.
Lo CW, Wu KG, Lin MC, Chen CJ, Ho DM, Tang RB, & Chan YJ (2010). Application of a molecular method for the classification of human enteroviruses and its correlation with clinical manifestations. Journal of microbiology, immunology, and infection, 43 (5), 354-9 PMID: 21075700

Tokarz R, Firth C, Madhi SA, Howie SR, Wu W, Sall AA, Haq S, Briese T, & Lipkin WI (2012). Worldwide emergence of multiple clades of enterovirus 68. The Journal of general virology, 93 (Pt 9), 1952-8 PMID: 22694903

Mirand, A., & Peigue-Lafeuille, H. (2015). Acute flaccid myelitis and enteroviruses: an ongoing story The Lancet DOI: 10.1016/S0140-6736(15)60121-0