If you’ve been following the stories in the media about the ongoing pandemic, you’ve probably seen both “COVID-19” and “Covid-19.” Which version is correct, and which one is Chicago style?
When it comes to the names of diseases and related terminology, our editors mostly defer to the usage of the organizations responsible for such nomenclature.
To see what this looks like, let’s start by distinguishing between the name of the virus, on the one hand, and the name of the disease that it causes, on the other.
The Virus and the Disease
The name of the virus responsible for the current pandemic is severe acute respiratory syndrome coronavirus 2, or SARS-CoV-2.
The name of the disease caused by SARS-CoV-2 is COVID-19, which stands for “coronavirus disease 2019.”
SARS-CoV-2 was named by the International Committee on Taxonomy of Viruses (ICTV), based on the recommendations of its Coronaviridae Study Group. COVID-19 was named by the World Health Organization (WHO), which publishes official names in the International Classification of Diseases.
These names were announced on February 11, 2020. Before that, the virus was referred to as 2019-nCoV, a provisional name that stands for “2019 novel coronavirus.”
For each of these names, Chicago follows the style reflected in the documents published by the ICTV and the WHO,* including the use of capital and lowercase letters.
If the virus name SARS-CoV-2 looks familiar, that’s because it is. SARS-CoV (without the “-2”) is the name of the virus responsible for the SARS outbreak of 2003. (SARS, or severe acute respiratory syndrome, is the name of the disease caused by SARS-CoV.)
Both SARS-CoV and SARS-CoV-2 belong to the species Severe acute respiratory syndrome–related coronavirus.†
Editors, take note: When the name of the virus is spelled out, it is styled in regular text and all lowercase: severe acute respiratory syndrome coronavirus 2. But the species name is in italics and begins with a capital letter: Severe acute respiratory syndrome–related coronavirus.‡
In all but the most technical contexts, however, you won’t need to refer to the official name of the virus or its species. You can simply refer to “the virus responsible for COVID-19” or “the COVID-19 virus.”
By a similar logic, “the coronavirus pandemic” and similar expressions can be used where it is understood that “coronavirus” is short for “coronavirus disease” (and specifically COVID-19).
COVID-19, Covid-19, COVID-19
Chicago normally retains capital letters in acronyms according to their listing in Merriam-Webster or another standard source (see CMOS 10.6). In the case of COVID-19, all caps is not only the style used by the WHO and, in the United States, by the CDC (Centers for Disease Control and Prevention), but it also reflects the entry for the disease in Merriam-Webster.
COVID-19 is also the preference of the Associated Press; see the AP Stylebook for a helpful overview.
In the New York Times, on the other hand, you’ll see Covid-19; the Times prefers an initial cap rather than all caps for acronyms of more than four letters (e.g., Unicef; an acronym is an abbreviation pronounced as a word). Covid-19 is also the style at the British newspapers the Guardian and the Observer, which prefer an initial cap rather than all caps for acronyms of any length (e.g., Sars).
You may have also run across the style COVID-19—for example, in the New Yorker, which prefers small rather than full-size capitals for acronyms in running text (but not in headlines). Some book designers, too, prefer this style, though Chicago doesn’t generally recommend it.
Finally, you may have seen the hashtag #COVID19. Hashtags can’t include hyphens or other punctuation, so this is the form to use.
* * *
In sum, Chicago style retains capital letters in COVID-19 and related terms as they appear in the documents published by the organizations responsible for such names. Other styles may vary.
* WHO is pronounced as an initialism (like EU) rather than as an acronym (like NASA). And though the World Health Organization generally refers to itself without the definite article (as in this press briefing from April 15, 2020), this post follows the more common practice of using a definite article before an initialism used as a noun (“the WHO,” but “WHO guidelines”).
† For a definitive overview of the naming process, see Alexander E. Gorbalenya et al. (Coronaviridae Study Group), “The Species Severe acute respiratory syndrome–related coronavirus: Classifying 2019-nCoV and Naming It SARS-CoV-2,” Nature Microbiology 5, no. 4 (2020): 536–44.
‡ You may have noticed a small departure from ICTV style here. Chicago calls for an en dash rather than a hyphen to connect “related” to the four-word compound that precedes it in the species name. See CMOS 6.80.
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