Is it Ebolavirus or Ebola virus?

7 August 2012

Filovirus virionWhen I drafted my article for TakePart (Don’t Panic – Ebola Isn’t Heading For You), I used the term ‘ebolavirus’ throughout, but the editors changed every instance to ‘Ebola virus’. Understanding which term is correct is far more complicated than you might imagine.

A new virus was first isolated in 1976 from patients during an outbreak of hemorrhagic fever in southern Sudan and northern Zaire. The name Ebola virus was proposed to describe the agent of this outbreak:

…the name Ebola virus is proposed for this new agent. Ebola is a small river in Zaire which flows westward, north of Yambuku, the village of origin of the patient from whom the first isolate was obtained.

The name was further modified with the subsequent finding of distinct isolates of the virus (e.g. Zaire Ebola virus, Sudan Ebola virus, Reston Ebola virus). In 2002 the virus names were contracted (Zaire ebolavirus, Sudan ebolavirus).

The way that viruses are named is regulated by the International Committee on Taxonomy of Viruses (ICTV). The current virus nomenclature for the Ebolaviruses is as follows:

Family: Filoviridae
Genus: Ebolavirus
Species (5)Bundibugyo ebolavirus, Reston ebolavirus, Sudan ebolavirus, Tai Forest ebolavirus, Zaire ebolavirus

This is why I used ebolavirus in the original draft of my article.

However, this new nomenclature did not work well, as summarized in a 2010 article, Proposal for a revised taxonomy of the family Filoviridae:

Five to eight years have passed since the introduction of the names Cote d’Ivoire ebolavirus [sic], Reston ebolavirus, Sudan ebolavirus, and Zaire ebolavirus for the members of the four recognized ebolavirus species. Instead of using these names, the overwhelming majority of publications refer to “Ebola virus” instead of Zaire ebolavirus, a preference that is also followed by the public press.

The authors conclude that introducing the name ‘Zaire ebolavirus’ was an error, and recommend reverting to the traditional virus name, Ebola virus:

Retrospectively, the virus nomenclature in most published articles will then be correct. Likewise, press articles, which almost invariably refer to “Ebola virus,” and usually with that term aim at referring to the virus that is currently officially named “Zaire ebolavirus,” will be correct retrospectively and prospectively. As the traditional names are different from the species names, confusing species and virus names will be much more difficult, even in the absence of taxonomic education.

When this proposal is officially ratified by the ICTV the nomenclature will be as follows:

Family: Filoviridae
Genus: Ebolavirus
Species: Tai Forest ebolavirus
Virus: Tai Forest virus (formerly Cote d’Ivoire ebolavirus)
Species: Reston ebolavirus
Virus: Reston virus
Species: Sudan ebolavirus
Virus: Sudan virus
Species: Zaire ebolavirus
Virus: Ebola virus
Species: Bundibugyo ebolavirus
Virus: Bundibugyo virus

This discussion leads us to the important difference between a virus and a species.  A virus species is defined as a polythetic class of viruses that constitutes a replicating lineage and occupies a particular ecological niche. According to the ICTV rules of nomenclature, virus species names are italicized with the first letter of the name capitalized (Zaire ebolavirus). Virus names (poliovirus) are written in lower case (except if a part of the virus name is a proper noun, e.g. Coxsackievirus) in non-italicized script.

The editors at TakePart changed my ‘ebolavirus’ to Ebola virus because that is the term they are familiar with. Using this name is not correct because Sudan virus, not Ebola virus, is responsible for the current outbreak in Uganda.

Incidentally, the virus I work on, poliovirus, is a member of the family Picornaviridae, genus Enterovirus, species Human enterovirus C. Poliovirus is the name of the virus. But you will often find it incorrectly called ‘polio virus’ in the popular press. At one time this virus was called ‘poliomyelitis virus’ which was shortened to ‘poliovirus’, not ‘polio virus’.

  • http://twitter.com/Drounz Audrey Richard

    Hi Pr. Racaniello,

    A few months ago I was struggling with the taxonomy of viruses while writing my
    PhD thesis since I didn’t want to be inaccurate or make sloppy mistakes in what
    was supposed to be the “culminating point” of my training. Back then
    I didn’t realize there was such an increasing discrepancy (that I was
    contributing to incidentally) as to the terminology of viral taxonomy.

    Since I read the piece of Kuhn and Jahrling (Clarification & guidance on
    the proper usage of virus and virus species names), I think that I finally use
    the terminology related to virus & virus species names much more
    appropriately than I did before.

    Now that I have understood that I shouldn’t use the name of a species – which
    is a taxon and therefore a “concept” – to describe those properties
    that should only be assigned to virions, I am much more careful. A great
    reminder for me is that taxa are created and can change over time but that virions
    are “tangible”, they are what they are and them only can be actually
    characterized (For instance, I used to say that a certain viral species was
    known to infect a certain host. Now I try to be more specific by saying that
    the virions belonging/assigned to this very species are what actually infects
    cells, not the taxon).

    The example given by Kuhn and Jahrling is kinda funny but helped me a lot: they
    say that we intuitively understand that a standard poodle and a German shepherd
    are very different although both being “domestic dogs”, meaning they
    both belong to the species Canis lupus
    familiaris. They explain that a standard poodle and a German
    shepherd are related enough on several levels (including genomic) to be grouped
    in a taxonomic class as low as the species BUT that it is also way obvious that
    both of them can still be easily discriminated based on many other factors
    (including genomic as well). So basically, they recommend thinking of virus and
    virus species names the same way.

    However, I can’t help finding that being accurate with virus and virus species
    names is a little less intuitive than it is with dog breeds and the species Canis lupus familiaris because in
    virology, many species are represented by only one strain/isolate sharing the
    same name as the species it is assigned to. And to be honest, though I
    think I’ve cleared my mind as to the virus I’ve been actually working on, I can
    still be a little confused when it comes to other viruses. Like the example you
    are actually giving right above!

    I did understand that the finding of distinct
    isolates was reason enough to create 5 distinct species within the genus Ebolavirus. But here is what I am not sure of: as long as
    the ICTV hasn’t ratified the revised version of the genus Ebolavirus, what would be the most accurate way to describe the
    current outbreak in Uganda? Should we say that Sudan ebolaviruses are infecting
    people and are responsible for the disease? Is that how the virions should be
    called based on the current, ratified taxonomy? Or do I not understand how the whole terminology of taxonomy works after all?

    Thank you very much in advance for your answer and sorry for having written such a long comment to ask such a short question…

    Audrey
     

  • Sven Enterlein

    I will try to get an answer from Jens Kuhn about this. There will be a new paper out in Archives of Virology soon taking the filovirus taxonomy to a new level. I can already predict that even within the filovirus community it will take forever for these changes to be accepted by everyone.

  • AJ Cann

    My feeling with these things is that it is best to make a distinction between formal taxonomy (and usage), and, where the public is concerned, clarity. As long as there is no confusion, ebola virus is more understandable to the average Joe than ebolavirus. And if that helps people approach the science and understand the issues, that’s why we publish in these media.

  • http://rybicki.wordpress.com/ Ed Rybicki

    Like the many, many instances of “papilloma virus”, even within my own group…B-(

  • http://twitter.com/cggbamford Connor Bamford

    My supervisors told me how people once tried changing the name of measles virus to human morbillivirus in order to make it easier to understand and place it into context with other related viruses. Truth be told this didn’t catch on and even if it was formally recognised I doubt people would have really stopped the usage of measles. 

    Once a name like that is out there you it will be very hard to put the genie back in the bottle so to speak. Same with something like mumps. As Alan says below, you’ve got to weigh up the pros and cons for the technical and lay communities. 

  • http://twitter.com/Drounz Audrey Richard

    To Connor B./AJ C.

    I admit that I don’t know much about Filoviridae in general or the genus Ebolavirus in particular but let’s say another distinct isolate is found but it’s not pathogenic. It’s assigned to this genus and a new species is created.

    Wouldn’t it be kind of misleading for people to be told that such a virus is (also) Ebola virus? 

  • http://www.virology.ws profvrr

    The purpose of viral taxonomy is to allow virologists to have a file system that makes sense, reveals similarities and differences, and to help guide their thinking. It is not to allow non-scientists to easily understand what a virus is or is not. If we simplify it for the public, we will lose its utility for virologists. I don’t know what the solution is, but I’ve always felt that dumbing down science is not the answer. On the other hand, if the article says ‘Sudan virus’, no one except virologists will know that it is an Ebolavirus. What’s wrong with saying at the beginning of the article, ‘Sudan virus’, one of the Ebolaviruses…’?

  • http://www.virology.ws profvrr

    Not sure about that. There was once a virus called Muerto Canyon virus, then Four Corners Virus, and it was changed to Sin Nombre virus and the latter name stuck. Maybe because the others were not out there for so long.

  • AJ Cann

    Formal taxonomy has it place. But in writing for the public (on general news websites), clarity trumps formality. Otherwise, you’d just tell the public to go and read your papers in PNAS.

  • guest

    Hi Vincent:
    Perhaps you could clarify, because it seems that your use of ebalovirus would be incorrect as well.  Or at least imprecise.  “Ebolavirus” only seems to be used to describe a genus, and you can’t be infected by a genus, correct?  Could you explain how you get from the current ICTV species names to just “ebolavirus” and why that is preferable?

  • http://www.virology.ws profvrr

    You are right, my wording wasn’t entirely correct. I used the term ‘Ebolavirus’ throughout the article, no italics. I should have used ‘Sudan Ebolavirus’ according to current nomenclature, or ‘Sudan virus’, according to the new nomenclature. One of my reasons for writing this post was to sort out this nomenclature issue.

  • http://www.virology.ws profvrr

    If you were to use the currently ratified nomenclature, the viruses infecting people in Uganda would be Sudan ebolaviruses. Unfortunately that’s the same name as the species, which, as you say, can be confusing. I don’t know what ICTV will eventually ratify for the Filovirus nomenclature, but in the proposed nomenclature, the viruses in the outbreak would be Sudan viruses. Few would know that this is an Ebolavirus. So as AJ Cann suggests above, the popular press should just continue with ‘Ebola virus’ even though technically that refers only to the Zaire species. 

  • jenshkuhn

    I only
    discovered this discussion now. As the lead author of the two papers discussed
    in this thread (and as the current ICTV _Filoviridae Study Group Chair) I hope
    I can clear up a few things.

     

    The new
    filovirus taxonomy as outlined in Dr. Racaniello’s blog has been fully accepted
    by the ICTV a few months ago (with the exception of the
    “cuevaviruses”, i.e. the proposed genus “Cuevavirus” and
    species “Lloviu cuevavirus” for the recently discovered filovirus
    Lloviu virus).

     

    If you take a
    step back, then you will quickly see that the new nomenclature now resembles
    that for many other viruses. The five viruses that, based on molecular data,
    clearly belong to five different species in the genus _Ebolavirus (the
    ebolaviruses) need to be considered as different entities, and therefore need
    to have different names. When deciding on names, the following considerations
    were taken into account:

    1.       Filovirus names should
    look like names for all other viruses, i.e. follow the format “xxx virus”.
    According to the nomenclature in place at the time of discussion, this was not
    the case (viruses were called Zaire ebolavirus, Sudan ebolavirus etc.)

    2.       Virus names should not
    be identical to species names, as otherwise virus and species can easily be
    confused (at the time, Zaire ebolavirus was a member of the species _Zaire
    ebolavirus etc.)

    3.       The right of the
    discoverer of a virus to name the virus should be respected and given names
    should not be changed if not absolutely necessary. As Dr. Racaniello points out
    correctly, the first ebolavirus to be discovered was given the name “Ebola
    virus” by Karl Johnson, not “Zaire ebolavirus”; and the first marburgvirus to
    be discovered was given the name “Marburg virus” by Rudolf Siegert (not “Lake
    Viktoria marburgvirus”). Confusion arose because other filoviruses were later
    discovered that at first looked like Ebola virus. Hence they were first named
    subtypes (Ebola virus Sudan subtype etc.) before they were recognized as
    distinct viruses and especially non-molecular biologists in the field have not
    yet fully accepted the fact that these five viruses are really five different
    viruses

    4.       Names should not be used
    when they prove to be derogatory (“Ivory Coast ebolavirus” was an unfortunate
    name because it’s a jargon term – not an official translation of the country
    Côte d’Ivoire; and there were objections to use “Côte d’Ivoire” in a virus
    name)

    5.       Abbreviations of viruses
    should not have the same pronunciation as it makes their use in talks pointless
    (at the time, the abbreviations for “Zaire ebolavirus”, “Sudan ebolavirus”, and
    “Côte d’Ivoire ebolavirus” were ZEBOV, SEBOV, and CIEBOV… )

    6.       Finally, to follow the
    rules of the ICTV, taxon names should be changed as little as possible.

     

    The Study Group
    therefore came up, among others, with the following solutions:

    1.       Re-instate the names
    “Ebola virus” and “Marburg virus” to honor the discoverers – which required
    abolishing the abbreviation ZEBOV (therefore replaced with the original
    abbreviation EBOV) but which allowed to keep the abbreviation MARV (which was
    also the abbreviation for “Lake Victoria marburgvirus”)

    2.       Keep the existing
    species names _Zaire ebolavirus, _Sudan ebolavirus, _Reston ebolavirus etc.,
    but change the species name _ Côte d’Ivoire ebolavirus (now Tai Forest
    ebolavirus)  to address the concern about
    “Côte d’Ivoire”

    3.       Change the names of the
    viruses assigned to the species _Sudan ebolavirus, _Reston ebolavirus, and _Tai
    Forest ebolavirus to Sudan virus, Reston virus, and Tai Forest virus. This made
    them different from species names, adhere to common virus naming conventions,
    and kept the word stems that everybody is used to (“here we infected with
    Sudan…”) – but these new names then required new abbreviations.

     

    Now, in a
    discussion outside of scientific circles, should we use “Ebola virus” for all
    ebolaviruses?

    Take, for
    instance, the henipaviruses. If you look into the press, you find very few
    articles describing a new “henipavirus disease outbreak” (or worse, a
    “henipa virus disease outbreak”). Instead, reports address Hendra
    virus disease outbreaks, or Nipah virus disease oubreaks – even though the
    disease caused by both, severe encephalitis, may be similar. It’s even more
    true if the disease is different (“Measles virus” vs. “Mumps virus” is of
    course used and not “paramyxovirus”).

     

    In the case of
    filoviruses, clear differentiation of viruses may be meaningful. Take, for
    instance, the current ebolavirus disease outbreak in Uganda. Ebola virus (EBOV)
    has never been detected in this country, whereas Bundibugyo virus (BDBV) and
    Sudan virus (SUDV) are endemic. BDBV and SUDV cause similar disease as EBOV
    with one important difference: lethality of BDBV and SUDV disease outbreaks is
    usually around 50% or lower, whereas EBOV disease outbreaks often reach 80% or
    more. EBOV therefore is “worse” than SUDV. Pointing out, in the press or in
    government reports, that the virus that causes disease in Uganda, SUDV, is
    related to Ebola virus (EBOV) might send a different message than saying that
    “IS Ebola virus”. On the one hand, the Ugandan government may increase awareness
    with using the catch phrase “Ebola virus” and people may modify their behavior
    and therefore decrease transmission. On the other hand, people may also become
    panicky and change their behavior that furthers spread (leave affected villages
    rather than go to a hospital upon suspicion of infection). A country will also
    get different international headlines depending on the catch phrase, which can
    affect trade (neighbor countries closing borders or stopping import of, say,
    meat products) and also tourism. Personally, for these reasons and of course
    for scientific accuracy, I would prefer headlines that state a “Sudan virus
    disease outbreak” in Uganda, and a specifying line in the article such as
    “Sudan virus, a relative of Ebola virus…”. This would make clear that the
    situation is serious, but also that it is not as serious as it would be in the
    case of an Ebola virus epidemic.

     

    Specific
    comments to individual posts:

    -         
    Guest:
    You are right, one cannot become infected with a genus (or a species or any
    other taxon). So, one cannot become infected with _Ebolavirus. But the members
    of each species have a vernacular name. The members of the genus _Ebolavirus
    (italicized, capitalized) are called ebolaviruses (not italicized, not
    capitalized). And therefore one can become infected with AN ebolavirus. This is
    why adherence to italicization and capitalization rules is important in virus
    nomenclature. This is exactly the same for all other virus groups: the members
    of the family_Paramyxoviridae are called paramyxoviruses; the members of the
    genus _Flavivirus are called flaviviruses and so on. By the way, there are no
    abbreviations for “paramyxoviruses” or “flaviviruses” - only for individual
    members of these groups. That is also the reason why there is no abbreviation
    for “ebolaviruses”, but there is one for one particular ebolavirus, Ebola virus
    (EBOV).

     

    -         
    Connor
    Bamford: of course, changing virus names just for the heck of it is silly.
    Measles virus will remain measles virus for a very long time and a change to
    “human morbillivirus” would only confuse everybody and be LESS precise (as I am
    sure there are human morbilliviruses other than measles virus out there).
    Likewise, I am not sure whether human herpesvirus 1 will ever catch on for
    herpes simplex virus 1. But in the case of filoviruses, this is different. If
    you go into PubMed, go search for “Zaire ebolavirus [title]” and compare that
    to “Ebola virus [title] ”. You will quickly see that Ebola virus has been used
    in 95% or more of all the publications. Now if you look into these publications
    you will see that the majority of them actually addresses what is now again
    called Ebola virus – namely the entity discovered in Zaire in 1976 by Karl
    Johnson. Very few papers actually address Sudan virus or the other
    ebolaviruses. Likewise, do the same exercise for marburgviruses. You will find
    only a handful of articles who use the name “Lake Viktoria marburgvirus” in the
    title (ironically, you will find one written by me), whereas all others use
    “Marburg virus”. The change of names we brought forward therefore simply makes
    correct what is used anyway; and “forces” changes on things barely used.

     

    -         
    And
    Audrey Richard is absolutely right, in my opinion, because the case he
    describes has almost already happened: Lloviu virus (LLOV) is a novel filovirus
    not known to be pathogenic to people. As a filovirus, it is related to
    ebolaviruses (although not closely enough to be grouped in the same genus
    _Ebolavirus), and of course the headlines therefore read “Ebola virus found in
    Spain”. Such a headline is more than misleading as it implies it is dangerous
    to go into certain areas of Spain…

     

    -         
    And
    one more time Audrey Richard: we used the dog breeds as a visual example for
    the difference between a species and individuals. This example is not entirely
    correct, as dog breeds are of course artificially selected for being
    particularly different. The right example would be you vs. me as examples of
    “isolates” of the members of the species _Homo sapiens (humans). The problem is
    that sample size in virology is still small. But I am sure we all agree that
    there are millions of viruses out there, not only the 3,000 or so currently
    described, and that hundreds, thousands or even millions of individual variants
    of each individual virus exist in all their individual hosts (think variants of
    a particular herpesvirus in the entire human population…). Taxa are designed to
    encompass all of these variants, even if they are not yet in our hands.

     
    Pheww. Sorry
    for being lengthy. I hope this was somewhat useful.

  • http://twitter.com/Drounz Audrey Richard

     Thank you very much for your great comment.

    As to your specific reply to me, I understand that the example you gave may have not been the “best” scientifically speaking, or the most accurate or whatever, but I really think it did fix things very efficiently in my head and made me much more careful, including in my PhD writing.

    As a matter of fact, being accurate in naming  the species and viruses belonging to the genus Ebolavirus seems even more relevant than simply making the difference between you and me, right? In the end, considering that it doesn’t matter to be specific as to whether a certain outbreak was caused by either Ebola virus or Sudan virus, both in the same genus but members of distinct species, is like saying that you and me (and everyone else incidentally) belonging to either Homo sapiens, or Homo neanderthalensis, or Homo habilis is “Potayto-Potahto” different, because it is the genus Homo after all.

    Anyway, I wouldn’t probably have realized these issues in the taxonomy of viruses without your paper. So it’s actually nice to have the opportunity to thank you for that.

  • Sven Enterlein

    Thanks Jens! Your reply is almost as long as your paper ;) We still have to meet for a beer!

  • Misha

    I realize this discussion is nearly 2 years old, but very glad it is out there. I am currently working on a couple of virology related projects but was unsure how to refer to them as my background is in parasitology (and before that, zoology). After reading the discussion below, I have just realized how biased my view of taxonomy has been until now, particularly with reference to the following points:

    1. The typical convention for naming parasites puts the genus name first, then species name, genus beginning with a capital letter, e.g. Plasmodium vivax. I had no idea that for viruses the order of nomenclature is reversed (it seems from the below discussion that the species name is first, then genus name?)

    2. In keeping with the above example, I would interchangeably refer to a patient with malaria as a patient infected with malaria parasites or a patient infected with Plasmodium vivax parasites (but I would not say “patient infected with Plasmodium vivax.” as that seems intuitively wrong). Sometimes clinicians use the phrase “patient with vivax malaria” which is analogous to the discussions below re keeping the balanace between correct taxonomic nomenclature and allowing the use of phrases that are sufficiently clear for the public (or professionals who do not have taxonomic training). I suppose it is easier when the lay terms for the organisms you are working with are completely different to their taxonomic name.

    3. I would previously have distinguished individuals from the same species as being able to exchange genetic information; just realised why this doesn’t work for viruses since I presume the only exchange possible is a (very?) indirect one (replicating in the same lineage of host cells if the first virus left behind a transposable element).

    This brings me to my question: if two viral isolates from different individuals are determined to be the same species, in reality they are directly related; differences could arise in related “individual” virus isolates due to mutation, insertion of transposable genetic elements, or incorporation of some of the host genome, etc but how many of these differences are sufficient to constitute recognizing a separate species? I can see the problem with the dog breed example below in this context; dogs of different breeds can still breed with each other and produce viable progeny (hence we can still call them the same species even though they are genetically and morphologically quite distinct) but this argument can’t be applied to viruses.

    @jenshkuhn:disqus: You mention that the 5 ebolaviruses were initially thought to be 5 subtypes of the same species but are now recognized as 5 different species only sharing a genus. How was this distinction made / what was the defining argument for relegating them each to their own species?

    From a gratefully enlightened (but also still a little confused) parasitologist…