Quarantine: Yeah, it's Complicated!

Quarantine: Yeah, it's Complicated!

Quarantine is not about Ebola! It is about protecting the health of the general public. It is about the law and science behind the decision to separate those who have been exposed to communicable and contagious diseases from those who have not. It is about balancing public health with the Constitutional rights of the individual and the factors involved in making such a critical decision.

Is quarantine potentially necessary for those exposed to Ebola? Absolutely! But, it's also potentially necessary for those exposed to tuberculosis, flu, measles, cholera, and any number of communicable diseases. Potentially.


Potentially means that professional discretion is required. That someone must make a decision based upon the evidence before them. And, for communicable diseases, the evidence includes the patient's history and signs and symptoms, and it involves the scientific evidence, as well as the laws of the states and the federal government.

And, unfortunately, for the elected dudes, discretion involves politics associated with the next election, the media spin, and the guidance provided by political advisers.

You see, regardless of the communicable disease in question, the decision of whether to quarantine an American citizen on American soil is like Nitroglycerin; if not handled correctly, it can blow up in one's face.

And when decisions are influenced by media driven hysteria and an approaching election, instead of patient history, signs and symptoms, law, and science, there will likely be some disfigured politicians. And when the elected dudes get disfigured, the appointed heads of agencies and departments often feel the pain.

Politics aside, how does one determine whether there has been an exposure to a communicable disease?  It starts with knowing what an infectious disease is, whether it is classified as communicable, and what determines if it is contagious or just a run of the mill communicable disease.

So you say, "Uh-dude, aren't communicable, infectious, and contagious like the same thing?"

Kind of, but not really–maybe. Confused? Hang in there.

Words Matter

Whether watching the news, reading the paper, or cruising the net to follow the Ebola crisis, one will hear and see many terms thrown around about Ebola, like it's an infectious disease, or it's contagious. Did I say contagious? I meant communicable.

Using technical terms makes the media dudes sound good, but words are too often improperly applied as if they are interchangeable. Maybe they are to the laymen, but definitions mean everything to the courts when deciding an appeal of a quarantine order. And that makes them important to the elected dudes and their appointees. Regardless, it is the failure to understand the terminology and the context, to which it is applied, that frames news stories that cause confusion among the public and is at least partly to blame for "interesting" decisions by the elected dudes.

We know that there are definitely communicable diseases and non-communicable diseases. And then, there are infectious diseases. But are there non-infectious diseases? Is an infectious disease also a communicable disease? How about a non-infectious disease? Is it always non-communicable?

Did someone say contagious? Huh? What are contagious diseases?  Are they not the same as communicable diseases? Is a contagious disease also infectious? Who's on first?

Confused? I am.

Communicable Disease vs. Non-communicable Disease

To start with, let's tackle the low hanging fruit. Discerning whether one is dealing with a communicable disease or a non-communicable disease is the first consideration point in deciding whether to issue a quarantine order. It is those with communicable diseases that have a high potential to transmit their funk to medical professionals and the community at large. And, as such, are the ones to be considered for quarantine or isolation.

The science guys at the Centers for Disease Control and Prevention (CDC) discern between communicable and non-communicable diseases as follows:

Non-communicable Disease:  Also known as chronic diseases, are not passed from person to person. They are of long duration and generally slow progression.

Examples of non-communicable diseases include:

  •  Heart Disease
  •  Stroke
  •  Cancer
  •  Asthma
  •  Tetanus
  •  Emphysema
  •  Diabetes
  •  Alzheimer’s
  •  Dementia

Communicable Disease:  An infectious disease that is contagious and which can be transmitted from one source to another by infectious bacteria or viral organisms. Examples of communicable diseases include:

  •  Flu
  •  Measles
  •  Pertussis
  •  Tuberculosis
  •  West Nile Virus
  •  Rabies
  •  MRSA
  •  Ebola

Now, given that non-communicable diseases cannot be passed from person to person, let's put them to bed and move on to understanding communicable diseases, like Ebola. Wait! Uhh... is Ebola a communicable disease or contagious disease? I am sure that it is infectious, right?

Now, I am sure you're like, "dude, does it really matter?" I really don't know yet. I'm a bit discombobulated.

Communicable vs. Infectious vs. Contagious

Hang on now. Understanding how communicable, infectious, and contagious differ is like watching a three-ring circus–with all rings in action–while talking on the phone, and ordering a hot dog from the vendor dude. Research is always the best way to raise the blinds on a complicated issue, right? I like to start with the simplest sources and go from there.

When you type the term communicable into, infectious and contagious are identified as synonyms. And then, when you click on infectious in the list of synonyms, contagious and communicable are displayed. But then, when you select contagious only infectious is displayed. Crap! It's no wonder we're confused.

Maybe some words of wisdom from a state department of health can help.

In describing a communicable disease, the website for the Wisconsin Department of Public Health Services states "[c]ommunicable diseases, also known as infectious diseases or transmissible diseases, are illnesses that result from the infection, presence, and growth of pathogenic (capable of causing disease) biologic agents in an individual human or other animal host."

Uh, guess what? The term transmittable is a synonym of infectious, communicable, and contagious. And transmissible is a synonym for only contagious. Yeah! That's what I said. So, is an infectious disease the same thing as an infectious or transmissible disease? 

Wisconsin's site continues, "[i]nfections may range in severity from asymptomatic (without symptoms) to severe and fatal. The term infection does not have the same meaning as infectious disease because some infections do not cause illness in a host."

Wonderful, now we have to add symptomatic and asymptomatic to the quarantine equation. And an infection is not the same as infectious? So when does one quarantine? Yeah, quarantine is complicated.

Let's check in with the science guys at the CDC for some help.

"People can be infected with dangerous diseases in a number of ways. Some germs, like those causing malaria, are passed to humans by animals," states the CDC website. "Other germs, like those that cause botulism, are carried to people by contaminated food or water. Still others, like the ones causing measles, are passed directly from person to person. These diseases are called 'contagious'."

Huh! So, does that mean that germs cause infections, but do not necessarily make one infectious? And if one is not infectious, they cannot be contagious?  But what about communicable?

Maybe a site written for the layman can help.

The website tries to help by explaining it in a way that even a firefighter can understand. "Some—but not all—infectious diseases spread directly from one person to another (i.e. blood, bodily fluids, or secretions). Infectious diseases that spread from person to person are said to be contagious."

The site goes on to state, "Some infections spread to people from an animal or insect, but are not contagious from another human. Lyme disease is an example: You can't catch it from someone you're hanging out with or pass in the street. It comes from the bite of an infected tick."

"Contagious diseases (such as the flu, colds, or strep throat) spread from person to person in several ways. One way is through direct physical contact, like touching or kissing a person who has the infection," the site states of contagious diseases. "Another way is when an infectious microbe travels through the air after someone nearby sneezes or coughs."

Ahh... better. But now we have two other terms to consider before issuing a quarantine order, airborne and direct physical contact. And I am still not sure where the line between communicable and contagious is drawn.

Fortunately, we have one more morsel of wisdom from the CDC to deliver clarity. Though communicable, infectious, and contagious are synonyms, the science guys at the CDC have blessed us with three definitions to learn:

  • Infectious Disease: A disease caused by a microorganism (virus, bacteria...) and therefore potentially infinitely transferable to new individuals. May or may not be communicable.
  • Contagious Disease: A very communicable disease capable of spreading rapidly from one person to another by contact or close proximity.
  • Communicable Disease: An infectious disease that is contagious and which can be transmitted from one source to another by infectious bacteria or viral organisms.

You guessed it, the term transferable is a synonym for communicable and contagious–but not infectious.  Miriam Webster defines transferable as "capable of being taken from one place to another by public carrier." For the sake of simplicity, let's assume the term public carrier applies to UPS, Fed Ex, and a person who is infected with an infectious funk and is considered communicable or contagious.

The takeaway from the CDC definitions is this: an infectious disease is potentially transferable (Can be transferred) to new individuals, but is not necessarily communicable. And if it is not communicable, it cannot possibly be contagious–I think. Where I am struggling is that the CDC definition for communicable disease states that it is "contagious." By their own definition, would that not make a communicable disease very communicable and capable of spreading rapidly, and thereby a contagious disease? What's the difference?

Maybe, it is time for the CDC to change their definition of a communicable disease? Maybe the science guys have just outsmarted themselves and everyone else, for that matter.

Or, maybe not. Heck, I am just a retired firefighter/paramedic, not a science guy. The problem is, every time I turn around, someone is saying "go to the CDC website for guidance." So, I do the same thing the elected dudes, police, cab drivers, toll-booth operators, firefighters, nurses, and the general public do. I go to the website and say, "huh."

Maybe the CDC needs a science guy site written at the level of the PhD epidemiologist and a laymen site written at the level of the common firefighter. I'll let you know if the CDC changes their definitions or if they provide some common-sense clarification that makes me feel like the dullest knife in the drawer.

Confused? Hang in there.


Before we move on to enhance our knowledge of quarantine and isolation, let's attempt to simplify what we have learned so far, but may not have yet understood.

  1. Diseases are either communicable or non-communicable.
  2. Communicable and contagious diseases are always infectious.
  3. Infectious diseases are always caused by a microorganism, such as a virus or bacteria, and are potentially infinitely transferable to new individuals.
  4. Infectious diseases, though transferable, may or may not be communicable.
  5. If an infectious disease is not communicable, it cannot be contagious.
  6. Contagious diseases are always communicable and infectious.
  7. Communicable disease can be transmitted from one person to another by contact or close proximity.
  8. Contagious diseases are very communicable diseases capable of spreading rapidly from one person to another by contact or close proximity.

For now, let's assume that the CDC definition for a communicable disease has a typo when stating it is contagious. With that assumption, we may be able to take a deep breath and accept that:

  1. Only infectious diseases that are also identified as being either communicable or contagious can be transmitted from one person to another by contact or close proximity.
  2. If a communicable disease is sub-classified as being a contagious disease, it is even more communicable than your run of the mill communicable disease, which means that it is very communicable and will spread more rapidly.

Oh! I failed to mention that some infectious diseases that are also communicable, like Ebola, are not transferable until a fever spikes. Yeah, maybe I shouldn't confuse you with that incubation period thing.

Since only infectious diseases that are classified as either communicable or sub-classified as contagious can be spread from one person to another, quarantine and isolation are in play – potentially.

Of course, based on one's discretion.

Next Up

  • CDC Definition for Quarantine: "Applies to those who have been exposed to a contagious disease but who may or may not become ill." Does that mean we never quarantine a patient exposed to a communicable disease?
  • CDC Definition for Isolation: "Applies to persons who are known to be ill with a contagious disease." Do we never isolate a patient with a communicable disease?
  • Constitution & Law: The federal government's authority, with regard to quarantine, was established with the the ratification of the Tenth Amendment of the Bill of Rights on December 15, 1791. The Tenth Amendment is the Commerce Clause of the Constitution that gives Congress the authority “to regulate commerce with foreign nations, and among the several states, and with the Indian tribes, and the Necessary and Proper Clause under the First Amendment."
  • Politics: Yeah, they are always in play when it comes to individual rights, state rights, and public safety.


Author's Note: This article was originally published on Friday, October 31, 2014. It was updated on Saturday, November 1, 2014 to provide clarifications.


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Karl Schmitt, MPA

Karl Schmitt, MPA

Karl is the Passionate Founder & CEO of bParati. He is on a mission to build a national network of effective, sustainable healthcare coalitions. More...

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