Why quarantine for measles is critical…and quarantine for Ebola was not

Measles has come to the happiest place on Earth. As of this writing, a total of 32 cases of measles have been linked to Disneyland visits that took place between December 17th and 20th. About 75% of the cases identified to date were not vaccinated, either because they chose to forgo vaccines or because they were too young, and at least 6 have been hospitalized.

A measles outbreak is a public health disaster, which can cost into the millions of dollars in health resources. You can be sure that public health workers in California and beyond are working overtime trying to identify cases, educate those who were possibly exposed about how dangerous measles can be, and implement practices so that those who may have been exposed to measles don’t further put others at risk. This includes avoiding public places, and practices such as calling ahead to a doctor’s offices so possible cases can be ushered into private rooms rather than languishing in the waiting room. A clinic in La Mesa recently closed because of a potential measles exposure. An unvaccinated South Pasadena woman, Ylsa Tellez, received a quarantine order after her younger sister was diagnosed with measles. Tellez is fighting the order and “taking immune-boosting supplements” instead.

Why such extreme measures on the part of public health?

Measles is highly contagious. It’s spread by air, and so contagious that if an infected person enters a room, leaves, and an unvaccinated person enters the room hours later, they still can contract measles. Remember a few months back, when that figure was circulating showing that Ebola wasn’t particularly easy to spread? Well, measles very much is. The basic reproductive rate for Ebola is around 2, meaning on average each infected person will cause an additional 2 infections in susceptible individuals.

And what’s the reproductive number for measles?

Eighteen. Eight. Teen. I’m not exaggerating when I say that it is literally one of the most contagious diseases we know of.  On average, if you have 10 susceptible individuals exposed to a measles patient, 9 will end up getting sick.

How do we break the cycle of transmission? Vaccination is one way–if one has been vaccinated for measles, chances are very low (but not zero, because nothing is perfect) that they will contract measles. Beyond vaccination, the next-best intervention is to keep those who are infected away from everyone else. The way we do this is by quarantining them.

In public health terms, quarantine specifically refers to the separation of individuals who have been exposed to an infectious agent, *but are not yet ill themselves,* from the rest of society. That way, they’re unable to spread the infection to others. Quarantine makes the most sense when individuals can transmit the infection before they realize they’re sick, which is exactly the case with measles. Infected individuals can spread the virus fully 4 days before the characteristic rash starts to appear, and continue to spread it for another 4 or so days after the rash begins—potentially infecting a lot of people. The problem is, like Ylsa Tellez, they’ll feel fine while they’re out there in the general population. They don’t even have to be coughing or sneezing to spread it (symptoms which can appear prior to the rash)—they can just be breathing (something many of us like to do on a regular basis), and still contaminate their environment with the measles virus.

The difference in transmissibility also makes measles a very different situation from Ebola. Public health officials almost universally condemned quarantine for Ebola exposures, for two reasons: 1) Ebola wasn’t highly transmissible, and  isn’t airborne like measles is; and 2) because Ebola isn’t efficiently transmitted until late in the infection when the patient is very ill and likely bedridden. Quarantining Ebola patients was a political stunt, not a public health necessity.

This is why states have the legal authority to enforce quarantine for infectious diseases: it reduces the risk that asymptomatic, potential disease-spreaders will act as “Typhoid Marys” (another asymptomatic, deadly-disease-spreader), which is in the public interest. And while unvaccinated Tellez feels “attacked” and her mother thinks people are being “not nice” when they demand that Tellez submit to quarantine, their choice not to vaccinate has already put many others at risk of disease and, and is resulting in the quarantine of many other exposed individuals as well. In the 2011 Utah measles outbreak, 184 were quarantined and thousands of contacts traced, at an expense of approximately $300,000. The Disneyland outbreak has already spread into 4 states (California, Utah, Washington, and Colorado). Quarantine is one of our tools to stem the epidemic. In our recent outbreak among Ohio Amish, most willingly submitted to quarantine, and over 10,000 doses of the MMR vaccine were administered. Quarantine is undoubtedly a difficult prospect to face, but perhaps if Tellez and others had been vaccinated in the first place, they, and we, wouldn’t be in this situation.