Know Your Variants: Kikwit vs Gueckedou

This is an update of an earlier post, Know Your Species: SUDV vs EBOV.

When last we discussed the Democratic Republic of Congo outbreak of Ebola, it was presumed that it was actually an outbreak of the genus Ebolavirus, species Sudan ebolavirus (SUDV), largely because that’s what initial reports indicated. It hasn’t yet been clarified why there were reports of a positive test for SUDV and a positive test for a SUDV/EBOV mix (although I’ve heard speculations about earlier outbreak exposure), but what we do know is that on 2 September, the World Health Organization released the results from their virological analysis, showing that while the Ebola outbreak in the DRC was actually EBOV (Zaire ebolavirus),See Maganga G, Kapetshi J, Berthet N, Ilunga B, et al. Ebola Virus Disease in the Democratic Republic of Congo. NEJM 2014;DOI: 10.1056/NEJMoa1411099. it also was not linked to the on-going epidemic in West Africa.I say “was” because there is currently no known active transmission occurring, and the country is in the cool-down period, waiting for 42 days to pass in order to be declared virus-free.

This brings us back to my last post illustrating Ebola with kittehs.The language of the internet. For a quick refresher, all ebolaviruses are the family Filoviridae and the genus Ebolavirus. There are five different species within that genus: Reston ebolavirus (RESTV); Taï Forest ebolavirus (TAFV); Bundibugyo ebolavirus (BDBV); Sudan ebolavirus (SUDV); Zaire ebolavirus (EBOV).

And then we have a obligatory illustrative cute cat picture, because this is just likeWell, with significantly less cuddles. how cats are members of the same family (Felidae) and the same genus (Felis), but have a variety of different species.

But what does it mean when we learn that, in fact, it’s the same species of ebolavirus, but different variant? Simply put, it just means being even more specific: variant fits inside species fits inside genus fits inside family.Are you having flashbacks to biology class yet? (Inside order. Viruses stop at that point; for the curious, the family Filoviridae is part of the order Mononegavirales.)

Variants are written out in a specific way that tells you the virus name, the isolation host-suffix, country of sampling, year of sampling, variant designation, and isolate designation. It looks like this:

Ebola virus H.sapiens-tc/COD/1995/Kikwit-9510621For more information on all of this, see: Kuhn J, Bao Y, Bavari S, Becker S, et al. Arch Virol. Jan 2013; 158(1): 301—311.

The current epidemic started with, it is presumed, a Guinea variant Guéckédou,The NEJM article discussing contact tracing back to a December case in Guéckédou. which would be written like this:

Ebola virus H.sapiens-wt/GIN/2014/Gueckedou-XXXXX

This tells us that it’s an ebolavirus infecting homo sapiens (that’s us humans), wild type (it hasn’t been cultured), that it was sampled in Guinea in 2014, and that the variant is Guéckédou.There is a brief post on Virology Down Under about this, too. (Don’t worry about the isolate. That’s basically an individual code that’s given per sample, hence the name.)

Clearly, at this point, it becomes harder to do a one-to-one correlation between viruses and kitties, because kitties don’t break down into variants and isolates, but work with me a bit here. What cats do break down into is year they were born, litter, and even what they look like. So we do have ways we tell each individual Felis catus apart, even though we recognize them all as belonging to the genus Felis and species catus.

In theory, we could roughly write these two cats out like this, utilizing their species, country of origin, year they were born, where they were born, and their name:

F.catus-wt/USA/2005/Philadelphia-Zeus

F.catus-ct/USA/2003/Cougar-ToledoYes, Toledo is from a place in Washington called Cougar. Honest.

Just as we can all look at Zeus and Toledo and see that they’re different domestic cats (but still clearly domestic cats, all the same), researchers can look at the virus they isolate from individuals and see that they’re different variants of the same strain. In the case of the outbreak in the DRC, it was a variant most closely related to the 1995 Kikwit Zaire ebolavirus outbreak.

So why does this matter? In an era of ebolanoia, it’s important to understand what it means when there’s an epidemic of Ebola in one area of the world and a new outbreak in another. People are quick to panic and assume that all outbreaks are connected to the epidemic, and equally quick to forget that ebolavirus has been cropping up sporadically for nearly 40 years in other parts of Africa. Knowing how scientists differentiate between strains and variants within viruses is another tool in being an educated and informed media consumer.