Disease Names, and How to Treat Them (At Least Editorially Speaking)

Health conditions are varied and complicated. They can cause pain, confusion, dizziness, slack jaw, belly aches… and that’s just their names!

Take for example Stein-Leventhal syndrome, polycystic ovary syndrome, chronic hyperandrogenic anovulation, CHA, and PCOS. As different as they look, these five have something in common: they’re all names for the same thing.

When you’re giving people health information, however, you should choose one of them and stick with it. Your English teacher may have taught you that variety makes for better text, but this isn’t a novel. This is health information. And people’s wellbeing depends on their getting the information, understanding it, and not being confused by it… which means you need to be consistent.

But how do you choose which name to use? What other things do you need to watch out for? And how do you keep it consistent and coherent?

The First-Line Treatment

One thing about disease names is that they can be really long. You don’t want to have to use “polycystic ovary syndrome” or “chronic hyperandrogenic anovulation” over and over again, so you call it PCOS or CHA (please pick one or the other!). But you should still make sure that your readers know what those initials stand for. Do that the first time you mention it.

Along with this, you will probably want to tell your readers about all the different names for a disease, so that if they see other names for it in other places they’ll know that they’re talking about the same thing. But, as we said, you need to be consistent; if you keep switching between names for the same disease, the reader may come to think there’s a reason for it – other than that you were taught to use “elegant variation.” So tell the readers about the other names, but choose one name to call it throughout, say that’s what you’ll call it, and stick with it.

"A condition known as PCOS, which stands for polycystic ovary syndrome (it's also known by the names Stein-Leventhal syndrome and chronic hyperandrogenic anovulation or CHA)."

Example 1: Pick the name (or abbreviation) you'll use and stick with it, but make sure the readers know about the others.

What Condition Is Your Condition Name In?

Once you’ve chosen what name to call a disease, your work is still not done. You need to make the right choices in capitalization, punctuation, and even italicization – and stick to them. For capitalization, follow your chosen style guide, which will likely advise lower-case by default, but note that there are some places where there’s only one right choice:

  • Proper nouns (names of people and places, such as in Lou Gehrig’s disease) are capitalized (but see below!).
  • The first word in a bacteria name is capitalized (but see below!), and the name is italicized.
  • The first word in a virus name is capitalized (but see below!), and the name is not.
  • Letters in acronyms (and initialisms) are capitalized, except when they’re not… see below.

You get the idea: the rules are simple… and simply loaded with exceptions. Let’s put them under the magnifier, starting with the acronyms.

The Initial Dosage

Your default treatment will almost certainly be to capitalize acronyms, as in PCOS and CHA. But don’t assume it’s all capitals all the time! For one thing, different style guides have different preferences, and this is especially true depending on which side of the Atlantic (or Pacific) you’re on: where Canadians and Americans put “AIDS,” for example, people in England and other countries are more likely to put “Aids.”

Beyond that, some abbreviations mix upper and lower-case. We’ve all seen SARS-CoV-2, alas; others that have lower-case letters mixed in include nvCJD (new variant Creutzfeldt-Jakob disease) and IgA nephropathy (where IgA stands for immunoglobulin A). The use of lower-casing may seem a bit inconsistent, but there’s always a reason for it… and that’s always a reason to double-check what the official usage is, and what your chosen style manual recommends.

And don’t go backwards from an acronym and capitalize the full name – writing Gastro-Esophageal Reflux Disease because it’s GERD, for instance. Unless your house style capitalizes all disease names all the time (say, for ease of reference), there’s no reason to do so.

Is It Really Proper?

Disease names often have proper nouns in them: Kawasaki disease, Duchenne muscular dystrophy, Ebola hemorrhagic fever… But don’t assume that something that looks like a proper noun actually is. For example, you might guess that the Ebola virus is named after a place, and you’d be right (it’s named after the Ebola River), but you might also guess that Chikungunya virus is named after a place or person, and you’d be mistaken: chikungunya is a word from Makonde, a language of Tanzania and Mozambique, and it’s a common noun meaning “that which bends up” – so it stays lower-case.

But wait! You can call the disease chikungunya or chikungunya fever, but you will still probably have to capitalize it in “Chikungunya virus.” Why? Because that’s the standard for virus names! So chikungunya is a disease caused by Chikungunya virus infection. Remember: when it’s the virus name, capitalize; when it’s the name of the disease, don’t capitalize unless it’s a proper noun (such as Ebola).

On the other hand, you can’t always assume that something isn’t a proper noun. You may know, for instance, that “legionnaire” is a common noun for a member of a legion. However, in Legionnaires’ disease, it is capitalized, because it’s named after members of the American Legion in specific, because its first known outbreak was at an American Legion convention.

Best to stick to the ABCDN principle: always be checking disease names (notice how that’s not capitalized?).

Are You Giving It the Right Slant?

As we just said, you have to watch out for viruses because they get capitalized (you should also watch out for them just in general, for your health). But bacteria are even trickier, and not just because they’re alive. The standard for bacteria in many styles requires attention to capitalization and to italics. Consider the serious childhood infection often referred to – not quite correctly – as “hemophilus influenza.” It is, in fact, an infection caused by Haemophilus influenzae type b bacteria (also spelled Hemophilus etc.), or H. influenzae for short. So when you refer to it, if you’re required to be technically accurate, it’s “Haemophilus influenzae type b infection” – or, for short, “Hib infection” (because the abbreviation is not italicized!).

Likewise, when 182 Legionnaires at a convention got a previously unknown respiratory infection and 29 of them died of it, the bacteria that caused it came to be named Legionella (specifically L. pneumophilia) after them. But, even though it’s Legionnaires’ disease, you can also call the infection “legionellosis” – no capital, no italics – because a derived name like that gets treated as a common noun. ABCDN!

How Possessive Should You Be?

Beyond capitals and italics, you also need to pay attention to punctuation. The apostrophe, as always, is a little agent of chaos. You need to make sure that you always put “Legionnaires’ disease” and never “Legionnaire’s disease,” for instance. And when a disease is named after a person (usually the one who first described it but sometimes, as in Lou Gehrig’s disease, someone who was afflicted by it), sometimes it gets the ’s and sometimes it doesn’t, for reasons that may seem capricious but are actually… pretty inconsistent. For instance, the disease named after Thomas Addison is Addison’s disease, but the genetic condition that was once called Down’s syndrome, after John Langdon Haydon Down, is now normally called Down syndrome without the ’s due to a recommendation by the National Institutes of Health. Likewise, the syndrome first reported by Tomisaku Kawasaki is normally called Kawasaki disease (or Kawasaki syndrome) and not Kawasaki’s disease.

There are also other details of punctuation to watch out for from time to time. A noted example of this is attention deficit hyperactivity disorder, which sometimes gets a hyphen (“attention-deficit”) and/or a slash (“attention deficit/hyperactivity disorder”). This is something you need to pay attention to – and, yet again, keep consistent!

Keep Up to Date

Along with all these factors to watch out for in the names of health conditions (and the things that cause them), you also have to make sure you’re not using a term that’s out of date, especially if the older term has bad implications. No one calls Down syndrome “mongolism” anymore, for very good reasons, and you would be unwise to call Alzheimer’s disease “senility.” But you also need to make sure that you’re talking about ADHD rather than ADD, and STIs (sexually transmitted infections) rather than STDs (sexually transmitted diseases) – let alone VD (venereal disease). And did you know that chronic fatigue syndrome (CFS) is now, by many authorities, called myalgic encephalomyelitis (ME)? Make sure you know what the authorities you’re following prefer. Also make sure you know which authorities you’re following!

Here’s a short list of some disease names that have generally been superseded, and the new preferred names to use instead.

Old term

New term

adult-onset diabetes

type 2 diabetes


alcohol use disorder

attention deficit disorder (ADD)

attention deficit hyperactivity disorder (ADHD)

blood poisoning

sepsis or septicemia

chronic fatigue syndrome (CFS)

myalgic encephalomyelitis (ME)

crib death

sudden infant death syndrome (SIDS)

insulin-dependent diabetes mellitus (IDDM)

type 1 diabetes

juvenile diabetes

type 1 diabetes


Hansen’s disease

mad cow disease

in cows, bovine spongiform encephalopathy; in humans, Creutzfeldt-Jakob disease (and others)

manic depression

bipolar disorder


transient ischemic attack (TIA)

non-insulin-dependent diabetes mellitus (IDDM)

type 2 diabetes


any of several diagnoses; find out more details

sexually transmitted disease (STD)

sexually transmitted infection (STI)

swine flu

H1N1 influenza (and others)

venereal disease (VD)

sexually transmitted infection (STI)

The Indicated Treatment

For all of the above, the indicated first-line treatment is a style sheet. Do your research and decide what name you want to use and how you want to capitalize it (and punctuate and italicize it), then record it and enforce it!

However, you don’t need to attempt to enforce this manually. If you’re a medical writer or editor, you’re probably working under time pressure. To help you save time, and to make sure you use your editing time for verifying the science, PerfectIt makes all of this easier. PerfectIt has several features that are specifically designed to help. These include:

  • Preferred Spelling: Enforce the choice of condition name as well as the spelling that you prefer.
  • Phrases to Avoid: Make sure no outdated names feature in any documents you produce.
  • Capitalization: Make sure each condition name is upper-case or lower-case in exactly the way they should be.
  • Abbreviations in Two Forms: If you’re using an acronym for a disease, make sure it’s consistent.
  • Abbreviation Definitions: Make sure each acronym is defined the first time you use it.

If that sounds like a miracle cure, it’s because PerfectIt is one of the best-kept secrets in medical writing and editing. It’s both affordable for freelancers and widely used in major corporations. It’s actually used across the medical writing team in six of the world’s top 10 global pharmaceutical firms.

If you haven’t used PerfectIt yet, the free trial is here. Give it a go – you’ll probably feel better very quickly!

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