A CDC Primer on Quarantine and Isolation

quarantineWhat is a quarantine, and what is the difference between quarantine and isolation? The CDC has issued a fact sheet and a Q&A on the subject.

Modern quarantine is used when a person or a well-defined group of people has been exposed to a highly dangerous and highly contagious disease, resources are available to care for quarantined people, and resources are available to implement and maintain the quarantine and deliver essential services.

Modern quarantine includes a range of disease control strategies that may be used individually or in combination, including: short-term, voluntary home curfew, restrictions on the assembly of groups of people (for example, school events), cancellation of public events, the suspension of public gatherings and closings of public places (such as theaters), restrictions on travel (air, rail, water, motor vehicle, pedestrian), the closure of mass transit systems, restrictions on passage into and out of an area.

Modern quarantine is used in combination with other public health tools, such as: Enhanced disease surveillance and symptom monitoring, rapid diagnosis and treatment for those who fall ill, and preventive treatment for quarantined individuals including vaccination or prophylactic treatment for some diseases.

Modern quarantine is more likely to involve limited numbers of exposed persons in small areas than to involve large numbers of persons in whole neighborhoods or cities, according to the CDC. The small areas may be thought of as “rings” drawn around individual disease cases. The CDC cites examples of rings:

– People on an airplane or cruise ship on which a passenger is ill with a suspected contagious disease for which quarantine can serve to limit exposure to others.
– People in a stadium, theater or similar setting where an intentional release of a contagious disease has occurred.
– People who have contact with an infected person whose source of disease exposure is unknown—and therefore may be due to a covert release of a contagious disease.

When someone is known to be ill with a contagious disease, they are placed in isolation and receive special care, with precautions taken to protect uninfected people from exposure to the disease.

When someone has been exposed to a contagious disease and it is not yet known if they have caught it, they may be quarantined or separated from others who have not been exposed to the disease. For example, they may be asked to remain at home to prevent further potential spread of the illness. They also receive special care and observation for any early signs of the illness.

The list of diseases for which quarantine or isolation is authorized is specified in a presidential executive order. The list currently includes cholera, diphtheria, infectious tuberculosis, plague, smallpox, yellow fever, viral hemorrhagic fevers (Ebola, Lassa, Marburg, Crimean-Congo, South American), Severe Acute Respiratory Syndrome (SARS), and influenza caused by  influenza viruses that are causing or have the potential to cause a pandemic.

Isolation lasts for the period of communicability of the illness, which varies by disease and the availability of specific treatment. Usually it occurs at a hospital or other health care facility or in the person’s home. Typically, the ill person will have his or her own room and those who care for him or her will wear protective clothing and take other precautions, depending on the level of personal protection needed for the specific illness. In most cases, isolation is voluntary, but federal, state and local governments have the authority to require the isolation of sick people to protect the public.

Modern quarantine lasts only as long as necessary to protect the public by providing public health care and ensuring that quarantined persons do not infect others if they have been exposed to a contagious disease.

Quarantined individuals are sheltered, fed, and cared for at home, in a designated emergency facility, or in a specialized hospital, depending on the disease and the available resources. They will also be among the first to receive all available medical interventions to prevent and control disease, including: vaccination, antibiotics, early and rapid diagnostic testing and symptom monitoring, and early treatment if symptoms appear.

The duration and scope of quarantine varies depending on the purpose and what is known about how long it takes for symptoms to develop after exposure.

If people in a certain area are potentially exposed to a contagious disease, state and local health authorities let people know that they may have been exposed and direct them to get medical attention, undergo diagnostic tests, and stay at home, limiting their contact with people who have not been exposed to the disease. Only rarely do federal, state, or local health authorities issue a manadatory order for quarantine and isolation. Quarantine and isolation may be compelled on a mandatory basis through legal authority, as well as conducted on a voluntary basis.

States have the authority to declare and enforce quarantine and isolation within their borders. This authority varies widely, depending on state laws. The CDC may detain, medically examine or conditionally release persons suspected of having certain contagious diseases. This authority applies to individuals arriving from foreign countries, including Canada and Mexico, on airplanes, trains, automobiles, boats or by foot. It also applies to individuals traveling from one state to another or in the event of “inadequate local control.”

The CDC regularly uses its authority to monitor passengers arriving in the United States for contagious diseases. In modern times, most quarantine measures have been imposed on a small scale, typically involving small numbers of travelers (airline or cruise ship passengers) who have curable diseases, such as infectious tuberculosis or cholera. No instances of large-scale quarantine have occurred in the U.S. since the “Spanish Flu” pandemic of 1918-1919.

According to the CDC, the need to use its federal authority to involuntarily quarantine a person occurs only in rare situations—for example, if a person posed a threat to public health and refused to cooperate with a voluntary request.


  1. Thanks for an informative article, Krystal. I’ll need to read it again, though, as I seem to have missed the part where it talks about soup.

  2. There are a number of journalists who have come back from West Africa who are undergoing some level of quarantine at present. For example, Lenny Bernstein of the Washington Post, who reported on Ebola in Liberia, is taking some measures of quarantine, although he is not under a mandatory quarantine order. He spoke on ‘On The Media’ last week about how he is working from home and “avoiding crowds” but gave no indication that he was in isolation.

    I think we should be careful about hounding reporters who have made it their mission to investigate what is happening in West Africa. It is thanks to their dedication and personal bravery that the international community has become aware of the scale of the issue. Their reporting has led to the much-needed public health response that was missing for much of this summer as the epidemic took hold. Snyderman’s crew shouldn’t have gone into a crowded public space after making a big deal out of their self-quarantine, but the reaction has gotten completely out of hand. The director of the CDC has specifically stated that Snyderman did not put the public at risk, in an interview to CNN reported by Nicole Mulvaney at NJ.com yesterday. I would like to see that statement more widely reported by Princeton’s media to inform people about the magnitude of the risk.

    The people who are calling for her to lose her medical license (I’m assuming it’s still current), to be fired, or for her to be arrested are completely off base. Snyderman has done great work and this one mistake, which- let’s recall- did not put the public at risk, should not become the defining feature of her career. We should celebrate that somebody who has done so much to promote public health chooses to make her home here in Princeton.

    1. Celebrate? Please. Man, you just won’t stop shilling for her, will you? LOL. Well, I guess everybody is entitled to a defense. Here’s the thing, without taking a position on whether it’s justified, I’d wager this will in fact be a, and maybe, the defining moment of her career. it will almost certainly define the end of it. It is very difficult to imagine NBC putting her on the air ever again. I mean, come on. They’re not going to embarrass themselves any further. There’s no shortage of TV docs; it’s hardly as if she has some unique skill set. Sure, the network may wait until after the quarantine, and she may just quietly disappear for the duration of her contract, but for all practical purposes, she’s done. And I don’t care how close she thinks she is to Hillary, any shot she may have had at Surgeon General in a potential Clinton administration is history. You think a political animal like Hillary is going to put her name up? Yeah, right. So basically she’s over. Is that fair? Maybe not. But she wouldn’t be the first person to wreck a career with a momentary lapse in judgment. You see, being a public figure (be it a media personality, movie star, politician or what have you) is a matter of perception as much anything else. Public personalities like her benefit from exaggerated positive perceptions, and milk them to build personal “brands” which they parlay into careers. The corollary is that when things go bad, negative perceptions are equally (or perhaps more) exaggerated and can destroy personal brands and careers just as quickly. Again, fair or not, that’s how it works. She played fast and loose with her image, trashed it, and that’s that.

      1. You may turn out to be right but I am a little skeptical. There is a news cycle and most of the networks haven’t made a deal about this story. The public health question is gone. The only thing left is whether Snyderman’s apology was ‘good enough’. I don’t think that’s a story that many people care about, apart from people like ‘the ladies of the View’, who make a living out of judging other women. On another note, it’s amusing to be called a shill on here again. It’s been a while since that last happened.

        1. Ha! Pleased to oblige! Seriously, though, I guess it could blow over, but I doubt it. The non-apology kicked things into overdrive IMHO. If you want a sense of how widespread the outrage with her and the dissatisfaction with her non-apology are, I’d suggest you do two things if you have not already: 1) go to Twitter and search “drnancynbcnews” and see what (and how much of it) comes up. 2) go to Dr. Nancy’s own facebook page, where she continues to get absolutely pummeled. Then let me know if you think she’s still viable.

    2. No one “hounded” Nancy Snyderman. She is a media personality and she was seen out and about after very publically agreeing not to be. Ms. Snyderman is a professional celebrity health reporter, her populist “credibility” and medical judgment is her brand and her product (from which she profits considerably). Leveraging her public credibility and celebrity, she made a very public statement to her viewers saying that she would be under “voluntary” quarantine. As a celebrity doctor who breached a promise to her viewers, the “commentariat” has every reason to be angry and disappointed in her, If she has breached the public trust and the public doesn’t trust her, then why should she have a job presenting medical issues to the public?

      But there’s more. As reported by the Associated Press, the NJ State health department indicated that Ms. Snyderman’s crew had violated an agreement reached with public health officials. So now the information available suggests that what Ms. Snyderman presented as a voluntary, unilateral, individual, self-regulated promise to quarantine seems to have actually been something more official than that, involving agreement with state officials (which she breached).

      So if we just go back to the facts here, Ms. Snyderman was part of a news crew reporting from Liberia and one of that crew tested positive for Ebola. She and her crew were under an agreement with NJ state health officials the crew is under quarantine for 21 days. A crew member breached the quarantine. SFB, in your own commentarianism here and around the net, you seem to try to keep an eye out for the “regular folks”, so I will ask you this: Do you really really believe, that if the breaching crew member was not an affluent, socially and politically connected celebrity, was not one who contributes money and serves on boards of the same boards with those in positions of influence, and one who was not a lucrative brand name for NBC, would that person still have a job with NBC after being outed for breaching the quarantine? Would that person be hired in any position involving medical judgment and advice- giving? If Nancy herself had kept quarantine, and if it was a different crew member who had breached, would the Dr. Nancy brand allow that person to stay with the Dr. Nancy team?

      And, finally, as others have commented, the issue that is troubling folks here is not so much about how much immediate infection risk Ms. Snyderman’s breach created, but more about the common social agreement we have to trust each other to keep order and keep everyone safe and healthy, from which we each individually benefit. Sociology 101 tells us that the main reason we stop at stop lights is not because we immediately fear police enforcement if we don’t, we stop at stop lights because we understand that if everyone abides by the social contract to stop at stop lights then we are all safer, and that there is order and fairness at the intersection. And we stop at stop lights even when we don’t immediately see a risk in not doing so. It’s the social contract. And when Ms. Snyderman who’s brand is (was) trust and leadership in public health behavior, breaches the public trust, we no longer have to buy her brand.

      (Oh, and the “apology”? I’m so sorry you were upset ….? Really Ms. Doc? Where’s the “I” in that apology? Where’s the ownership? Where’s the respect for those that were “concerned”? Please.)

      1. Snyderman was in an enclosed car. She didn’t expose herself to anyone. Capisci? Moreover, she posed no threat, and the fact that she’s a “celebrity doctor” doesn’t change that a bit.

      2. There’s something in this story that makes no sense. Why would Snyderman’s crew be stationed at her house? Don’t they have homes of their own, and families?

  3. MRSA did not make this list and that has contributed to a lack of preparation by hospitals. The nurses are right that protocols are not in place. Unbelievable. The CDC and medical staff has had more than a decade to practice and put protocols in place with the increasing number of highly dangerous, highly contagious MRSA infections in the community. Instead, patients were sent home and back into the community repeatedly and they’re still being sent home instead of being isolated. Even those who have come into contact with an active MRSA infection are not quarantined. MRSA Survivors says stats show more people are dying every year in the U.S. of MRSA than AIDS/HIV. Yet it is ignored. No media is willing to mention deadly, highly contagious MRSA and I don’t know why. Thousands are people are dying annually, it is estimated more than a million people in the U.S. are infected with MRSA every year (and I believe that estimation), yet patients are misdiagnosed and sent home or diagnosed and still sent home. Now, everyone is scrambling. What a mess.

      1. There are random articles, but not daily stories from the media about MRSA as there have been about Ebola. And I have seen no major network media mention MRSA yet when talking about Ebola spreading in the hospital setting and community, where MRSA is also spreading.

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