The Disneyland measles outbreak reminds us that it’s still a very dangerous disease

Measles may not be an everyday concern in the United States, but it’s still a very contagious, and very dangerous, disease. While it was largely eradicated in this country after the measles, mumps and rubella (MMR) vaccine was introduced in 1967, the CDC estimates that worldwide, 20 million people get measles and 146,000 die from the disease each year.

The recent outbreak centered on Disneyland in California, which has led to at least 74 cases in 7 states and Mexico, is a reminder that the disease can strike at any time given the right conditions. Officials suspect that the current outbreak may have started when an infected person visited Disneyland in December, and the disease spread among other visitors and workers who are unvaccinated or under-vaccinated, because of lack of access, opposition to vaccines in general, or the belief that measles isn’t a serious illness.

To find out more about measles, how serious it is and why this preventable disease is suddenly in the news again, I spoke to Allison Bartlett, MD, Associate Medical Director of the Infection Control Program at the University of Chicago Medicine Comer Children’s Hospital.

Allison Bartlett, MD

Let’s start with the basics: What is measles, and what are its symptoms and complications?

Measles is an infection caused by a virus. Its symptoms include fever, cough, runny nose, rash, and red eyes, or conjunctivitis.

In addition to the fever, cough, etc., there are other complications: ear infections in 1 in 10 children, 1 in 20 get pneumonia, and 1 in 12 get diarrhea. The really serious complication is acute encephalitis, an irritation of the brain, which can result in permanent brain damage in 1 of every 1,000 cases. In the US, death from neurologic or respiratory complications occurs in 1 to 3 cases per 1,000. In addition, there is a late onset complication called subacute sclerosing panencephalitis, or SSPE, that is a rare, degenerative and fatal central nervous system disease that can occur 7 to 10 years after measles infection.

How contagious is measles?

Measles is one of the most highly communicable infections there is. It’s spread through direct contact with infectious droplets or through the air. Before immunizations, 75 percent of people exposed for the first time became infected. People are contagious from 1 to 2 days before symptoms start and remain contagious for 7 to 10 days.

Why is it making a comeback now?

Thanks to the success of measles immunization, it’s no longer endemic in the US. Measles is generally imported from another country, and infection spreads locally among un-immunized or under-immunized people.

One of the justifications people give for not getting vaccinated for measles is that they don’t think it’s very serious, and if they do catch it they’ll survive.

I saw a statistic recently that puts that into perspective. The vaccine was introduced in 1967, and a study looked at measles cases in the US between 1967 and 1985. They calculated that the vaccine prevented 5,200 deaths and 17,000 cases of mental retardation during that time. So it’s not a benign illness. Today we think of it as no big deal, and fortunately for most people it’s not a big deal—but the problem is you can’t tell for whom it’s going to be a big deal and who it’s not. Like I said before, 3 in 1,000 kids who get the measles will die. The odds are in your favor, but if everyone is vaccinated, 0 out of 1,000 kids will die. Before the vaccine, there were 500 deaths a year in the US from measles, and now it’s completely preventable.

People don’t appreciate the seriousness of measles. With all of these vaccine preventable illnesses, most people don’t get sick. I also don’t get in a car accident every time I drive, but that doesn’t mean I don’t protect myself and wear a seatbelt when I do.

Another rationalization about not getting the vaccine is that people think measles only affects kids from third world countries with poor nutrition or substandard living conditions and medical care. Is that true?

There are a lot of things that increase your susceptibility to infection, and certainly poor nutrition contributes a lot. Things that contribute to the spread of measles are crowding, which is potentially why we think of it in the third world, but that’s also why it spreads during an epidemic in a school, or a place like Disneyland. I think the other thing where the so-called sanitation argument breaks down is that there are definitely pathogens where contamination of drinking water can cause problems, but measles is spread is through contact with infected droplets. It’s airborne, and it hangs around in the air for several hours after the person leaves. So no amount of washing your hands—which obviously I’m a big supporter of—is going to fix the fact that there’s measles in the air that you’re breathing.

When should children get vaccinated? How often or how many times?

Children should be vaccinated after their first birthday and should receive a booster before entering kindergarten, when they’re 4-5 years old. We know that the first vaccine does not work for about 5 percent of people, which is why the second “booster” dose is given.

Why is it important for everyone to get vaccinated for diseases like measles?

Individually, vaccination is important to prevent infection and the complications. On a societal level, it’s important to remember that infections like measles cannot be treated, but they can be prevented. There are vulnerable people—children less than 12 months old, people with abnormal immune systems like those undergoing cancer treatment—who are unable to receive the vaccine, and whose bodies are not as able to fight off the infection. We know that “herd immunity”, or having a high proportion of vaccinated and immune individuals can prevent epidemics. Because measles is extremely contagious and can spread through the air, for example, the immunity threshold needed to protect a community is high, at 95 percent. While a large population may have a high enough percent of vaccinated individuals, sub-populations may exist with a much lower percentage of immunization. It’s in these groups that epidemics can take off.

Can you still get sick even if you get the vaccine?

No vaccine is perfect. There are some people who fail to respond—that’s just the way their bodies are. And there are some people who just do not have as robust a response as others, but even in those cases there’s protection offered by the vaccine. You may still get the measles, but you won’t get the serious complications, and your chance of dying is much lower. So while prevention of measles, or any infectious disease, is the ideal goal, preventing people from getting as sick is also an admirable secondary goal.

This is what we think we’re seeing with the flu vaccine this year. It’s not as effective at completely preventing the flu as we would like, but it does seem to be that people aren’t getting as sick with the flu, so there’s still some impact from the vaccine.

And when more people get the vaccine, there’s less chance of it sneaking through on someone who doesn’t respond for whatever reason.

Exactly. One of the reasons they started doing the second dose of measles vaccine is that we know that 5 to 20 percent of people don’t respond to that first dose, but if you go on and give everyone a second round, the rates of response are much higher. That was started because the public health community was seeing more measles cases than we would’ve expected compared to the vaccine coverage.

Is there any cause for alarm if, say, there was a case of measles in Chicago?

I think it’s concerning. There are certain groups who should be more concerned. I think having a case present in an ER would be more concerning, depending on how quickly it was identified and the patient was placed under the appropriate airborne isolation, because a bulk of the patients coming to the ER are not healthy in the first place. Depending on how the child became infected and the population they live in matters. We happen to know that under-vaccinated people tend to congregate together. If you happen to be a member of a community with a large number of under-vaccinated people, then it’s potentially very worrisome. The number of people who get sick when exposed to measles is very high if they’re not vaccinated. So the overall vaccination numbers in a city may be good, but that’s not where the outbreak is going to spread.

Are vaccination rates high enough in Chicago and Illinois to prevent a big outbreak here?

I think the vaccination rates are good enough that we generally don’t have a problem. I don’t think across the board that they’re good enough that if we have several cases, we are not at risk for more spread. In a large city like Chicago, there are substantial pockets where the vaccination rates are low and concerning, and that may be thousands of people. So that’s where it gets concerning, with density.

About Matt Wood (491 Articles)
Matt Wood is a senior science writer for the University of Chicago Medicine and editor of the Science Life blog.
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