I noticed the usage on the CDC website. I don't understand why Zika is capitalized while the other two were in lower cases.

There is no vaccine to prevent or medicine to treat chikungunya virus infection.

There is no specific treatment for yellow fever; care is based on symptoms.

Zika virus disease (Zika) is a disease caused by Zika virus that is spread to people primarily through the bite of an infected Aedes species mosquito.


4 Answers 4


"chikungunya" and "yellow" are, respectively, a common Makonde word meaning "something bending up", and a color name.

Therefore, neither is capitalized.

However, "Zika" is a proper noun, named after a forest in Africa; therefore, it's capitalized.


Capitalization is stylistic choice, and people may choose to capitalize things that you don't normally see capitalized. There are a couple of guidelines that come up in a simple search, and this is one of them. There's no unilateral consensus, but there are conventions. Chicago Manual of Style is another eminent manual that is both loathed and loved at the same time.

Back to your question, just like most of the words in this sentence, words in text and descriptions shouldn't be capitalized by default. That explains the yellow fever's case.

In the other two cases, the origins of the words are helpful:

History of "Zika virus"

The virus was first isolated in April 1947 from a rhesus macaque monkey that had been placed in a cage in the Zika Forest of Uganda, near Lake Victoria, by the scientists of the Yellow Fever Research Institute. A second isolation from the mosquito A. africanus followed at the same site in January 1948. When the monkey developed a fever, researchers isolated from its serum a "filterable transmissible agent" that was named Zika virus in 1948.
emphasis mine

Thus, "Zika" is the name of a forest, and generally proper nouns, including the names of places, get capitalized.

History of "chikungunya"

The word 'chikungunya' is believed to have been derived from a description in the Makonde language, meaning "that which bends up", of the contorted posture of people affected with the severe joint pain and arthritic symptoms associated with this disease.

Often terms that enter English from foreign languages don't get capitalized. There is a related question on this on ELU.

  • 12
    +1 Some other examples of often-capitalised disease names: Ebola after the river in DRC, Marburg after the German city, Lassa fever after the town in Nigeria, West Nile fever after the river/region, Alzheimer's and Asperger's after the psychiatrist who recorded the first case, etc etc. All are named after a person or place. Commented Feb 29, 2016 at 14:34
  • I am confused, I thought the name of each disease would be a proper noun and therefore capitalised. The first link in this answer points to a page that says "we capitalize words that are proper nouns—that is, they describe a specific thing or entity. They could be a title, a name..." and in this case the words are the names of diseases, so proper nouns? Commented Mar 2, 2016 at 20:29
  • @Ian No, the problem of that definition is that its incompleteness is misleading and confusing. Would you also call carpet, bottle, and castle proper nouns? Would you call foot, leg and arm proper nouns, since they're a name after all? I'm more inclined to think of it this way: Any noun that can reasonable be a vocative in your mind is very likely to be a proper noun. Other than that, I Can Capitalize Anything I Like, Like The Words In This Sentence. It Just Would Garner Weird Looks, like the way you're looking at me right now.
    – M.A.R.
    Commented Mar 2, 2016 at 20:35
  • I'm not convinced (although every reference to these diseases doesn't capitalise them). I would call all of your examples common nouns, but if you'd listed a particular castle by name it would be a proper noun. These are diseases (the common noun) and the specific name, in the same way my name is Ian, are yellow fever and the other chikungunya. I realise I'm wrong saying that because I can see the overwhelming evidence to the contrary (Wikipedia and NHS website), but nobody has explained why either they are not proper nouns or why they are not capitalised if they are proper nouns. Commented Mar 2, 2016 at 22:15
  • 1
    By all means @Ian. I suspect you're on the right track. The answers here are meant to be as easily comprehensible by learners as possible. I would love to see an answer that digs a lot into this stuff, but I suspect the only correct answer when it gets to capitalization is "They (did not) capitalize because they did not."
    – M.A.R.
    Commented Mar 3, 2016 at 6:20

The Zika virus is named for the Zika Forest in Uganda. Given that Zika is a proper noun, it is capitalized.


Since Chikungunya and Yellow Fever are names of diseases, they are Proper Nouns, regardless of their origin. So is Zika. Hence they must be capitalized.

You can also capitalize on occasion to emphasize something, as I have in the first sentence.

  • 1
    You should not capitalise to emphasise something, but sadly the world's marketing people have forced this down our necks for the last couple of decades and it's becoming accepted. I agree with you on the other point, even though I'm wrong and I don't know why. Commented Mar 2, 2016 at 22:28
  • "They must be capitalized." . . . in your writing. ;) I still don't know why people are considering an answer right or wrong here, since this is all about conventions. There has never been a capitalization guide people unanimously follow. The OP wanted a convention explained, not a rule, not a law.
    – M.A.R.
    Commented Mar 3, 2016 at 6:25
  • Well, the convention exists because of the rule, right? :-)
    – Chiwda
    Commented Mar 4, 2016 at 3:54

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