Let Me Out!

Earlier this month, commuters in the San Francisco area were warned that they may have been exposed to the highly contagious disease measles after a student at University of California, Berkeley attended class and rode the Bay Area Rapid Transit (BART) while contagious. The student, who was unvaccinated, likely contracted the disease while traveling abroad. Take a virus that can remain viable in the air of an enclosed space (like a classroom or subway car) or on surfaces for up to about two hours, a large student population of a university like UC Berkeley, and hundreds of thousands of commuters each day and you have a lot of people that were likely exposed to one of the most contagious viruses known to infect humans. Just look at BART alone, which sees roughly 390,000 riders each day. Of course, not all of those will ride in the same car as the student, but we can expect that at the very least, several hundred people would have been exposed to measles each time he rode. Cars hold about 60-70 people, the virus lingers for a couple hours, lots of people getting on and off during that period, it adds up. We could see additional cases popping up over the next week or two. And that's not the only case that California has seen. As of February 21, there have been 15 cases of measles, with the youngest being only 5 months old, according to a CDPH teleconference. Compare this to last year, when there were only 2 cases by the same date.

Those 15 cases make up the majority of the 24 cases seen nationwide to date, with other cases seen in Hawaii, Massachusetts, New York, Oregon, Pennsylvania, Texas, Washington and Wisconsin. The cases are in those who traveled to other countries where there are current measles outbreaks (e.g., the Philippines) or where measles is endemic (e.g., India) or among those who have had contact with someone bringing the virus back from another country. Since measles was eliminated from circulation in the U.S. in 2000, the outbreaks we have seen since then have been due to importation by unvaccinated individuals, some too young to be vaccinated, and others intentionally unvaccinated. Note that none of the outbreaks in recent years has been started by a fully immunized individual. With the risk posed by importation of the disease, I started to think about what role quarantine might play in mitigating potential harm to the public.

First, let's get some definitions out of the way. As far as the law is concerned, "isolation" involves only individuals who are known to be ill, while "quarantine" involves any healthy person, animal or object that was exposed to a contagious disease. For purposes of this post, I'm just going to stick to people, especially since measles only infects humans. In order to protect public health, could the government isolate or quarantine individuals entering the U.S. from a foreign country if they showed signs of measles or were exposed to measles? Would it be reasonable to do so? Are there drawbacks? Would it work?

I Hereby Grant You Authority 

The government, whether local or federal, has long had legal authority to quarantine and isolate individuals in an attempt to prevent the spread of infectious diseases. Early on, it largely left it to individual states and local jurisdictions to handle things, but in the late 1800s, Congress finally passed legislation codifying the federal government's minimal role in quarantine. It wasn't until 1944, with the passage of the Public Health Service Act, that the federal government's authority was firmly established, as states realized centralized, coordinated control of quarantine centers by the federal government would work better. The current federal powers are established in 42 U.S.C., Chapter 6a, Subsection II, Part G. Regulations further detail how the government is to go about enforcing those laws on the domestic, interstate level (see 42 CFR 70) and the international level (see 42 CFR 71). In addition to federal powers, the states also retain their own quarantine powers. So even if the federal government might not do anything, the individual state still could.

As far as measles goes, federal officials would not (currently) be able to legally apprehend and detain an individual who was exposed and likely to become ill but still healthy, because measles is not on the current list of quarantinable communicable diseases. The President, at the recommendation of the Secretary of Health and Human Services and in consultation with the Surgeon General, issues Executive Orders to list the diseases for which the government may quarantine people. If a disease isn't on the list, then people with that disease can't be held or prevented from traveling...at least by the Feds. The current list (Executive Order 13295 of April 4, 2003) only includes the following diseases:

Cholera; Diphtheria; infectious Tuberculosis; Plague [Bubonic plague]; Smallpox; Yellow Fever; and Viral Hemorrhagic Fevers (Lassa, Marbug, Ebola, Crimean-Congo, South American, and others not yet isolated or named)...[and] Severe Acute Respiratory Syndrome (SARS).

The list was amended by Executive Order 13375 of April 1, 2005 to add influenza strains that have caused or have the potential to cause a pandemic. The diseases listed pose a high risk of death or serious injury to those infected. For example, diphtheria (which can be prevented by a vaccine) kills about half of those who are infected and do not receive treatment. Even with treatment, the death rate can be as high as 10%.

The list of quarantinable diseases is necessarily limited to prevent abuse and unreasonable detention of individuals. Although the rate of measles in recent years has been very concerning and significantly higher than it should be (see, for example, the large outbreaks in Indiana and Minnesota), it's not (yet) at a level that would lead to endemic transmission. So, it's unlikely that it would be added soon. But if more people refuse the MMR and measles rates continue to rise toward the levels seen in the U.K., France or Pakistan, that could change. While not as fatal as diphtheria or Marburg, measles can still kill around 1-2 people per 1,000 infected, and it is much more readily transmitted from person to person than the other diseases on the list, infecting ~90% of susceptible people. If more people decide to believe hype and propaganda over reality, we could see measles added to the list sooner rather than later (or never).

Wait Over Here, Please

Federal authorities work closely with state and local health agencies, as well as transportation companies. The airlines, cruise companies, bus lines are the first line of defense. When they learn that a passenger is ill, they're required to report it to the port before they get there. That allows port authorities to take measures to keep other passengers and employees safe. But what if no one has any noticeable symptoms? If one of them is incubating measles, how do you go about preventing the spread?

One option is to figure out where the passenger is coming from. Are they entering the U.S. from a country where measles is endemic or in the midst of a large outbreak? If not, then it's probably safe to just allow them in without any further action. Otherwise, the next question to ask is are they already immune? The CDC has several ways to determine immune status:

• blood test showing immunity
• born before 1957 (before the vaccine, nearly everyone is assumed to have had the disease)
• documented receipt of two doses of measles-containing vaccine
• documented receipt of one dose of measles-containing vaccine and at low risk of exposure

Anyone who is considered immune and at low risk of infection could be let into the country, while those who aren't might end up facing quarantine or some other action. That could involve quarantining the individual before they're even allowed into the public areas of the airport, port or station. Or they might be given medical treatment to render them non-contagious. Countries that require proof of yellow fever vaccination provide examples of what people might experience when entering the U.S. from a measles-endemic region:

Travelers who arrive in a country with a yellow fever vaccination entry requirement without proof of yellow fever vaccination may be quarantined for up to 6 days [the incubation period for yellow fever], refused entry, or vaccinated on site. A traveler who has a specific contraindication to yellow fever vaccine and who cannot avoid travel to a country requiring vaccination should request a waiver from a physician before embarking on travel (see the Medical Waivers [Exemptions] section below).

For measles, the quarantine period would be about 14-21 days, the time it takes for symptoms to appear. Unlike for yellow fever, immunization with a measles-containing vaccine may not provide immunity if a person has already been exposed, especially if more than 72 hours has passed, but it could still be offered or required if someone wants out of quarantine.

But I Have Stuff to Do!

While quarantine can be an effective means of preventing importation of measles, it may not be as easy as just saying those who are at risk of the disease have to stay in quarantine for 14-21 days. Every person that is put in quarantine is kept out of the workforce. If they are traveling on business, their project may be delayed. They might lose income. On the other hand, they could avoid quarantine by vaccinating, barring a valid medical contraindication, in which case a waiver may be granted. The impact of the quarantine has to be weighed against the risk of an outbreak.

Another consideration is that forcing someone into quarantine may cause a negative backlash. It may provoke people to escape quarantine, thereby undoing any public health benefits of the measure. Involuntary quarantine is also a rather heavy-handed act that could increase civil disobedience, dislike and distrust of the government or health agencies. Again, the risk of these negative effects must be weighed against the risk of the disease getting out into the public.

Forget This, I'm Leaving

Quarantine can be very effective when it is voluntary. The situation is explained to the individual, and they choose to go into quarantine in order to protect those around them, whether family, friends or strangers. Choosing altruism over selfishness. As I hinted above, though, quarantine isn't always effective, since people might decide they would rather go about their daily lives than protect their families and communities. This is especially a problem when people mistakenly believe that measles is a benign, harmless disease. Breaking quarantine was a regular problem in the early 20th century smallpox epidemics. In those cases, quarantine jumpers helped spread smallpox to healthy communities, necessitating more quarantines and elevating tensions between public health and government personnel and the public they were trying to protect.

Because quarantine is not something to be applied lightly and without good justification, and the risk from diseases like measles can be quite serious, violating quarantine laws necessarily carry consequences. There may be federal penalties or state penalties, involving a fine, imprisonment or both. Those who place more value on their "right" to leave the airport and hop the subway home over the health of an infant riding a couple seats over probably won't be deterred by these legal wrist-slaps, though.

Quarantining healthy individuals when they enter the country is an extreme measure. Whether or not to implement it must be based on the circumstances unique to the people who are arriving from overseas. If we ever get to the point that measles importation is close to making the disease endemic once more, quarantine of healthy, non-immune people entering the country may be justified. There's no denying that keeping people who may carry the virus separate from the community until we can be sure if they're sick or not can be very effective at preventing outbreaks. But it's a complex issue that would take time to work out how best to go about it. In the meantime, wait over here in this lovely hotel room for a couple weeks. Don't mind the lock on the door.
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Further reading:

CDC:
History of Quarantine
Laws and Regulations
About Quarantine and Isolation
Measles Guidance for Commercial Aircraft Operators

Federal Laws:
42 USC Chapter 6a, Subchapter II, Part G, Sections 264-272

Federal Regulations:
Interstate Quarantine: 42 CFR 70, Sections 70.1-70.9
Foreign Quarantine: 42 CFR 71, Sections 71.1-71.56

California Laws:
General Provisions: HSC 120100-120115
State Functions: HSC 120125-120155
Local Functions: HSC 120175-120250
Notification: HSC 120260-120263
Violations: HSC 120275-120305

CDPH Isolation and Quarantine FAQ