Measles 'patient zero' and why outbreak might not be over
The rate of new measles cases in the suburbs has slowed, but the state's top public health official says it's not yet time to consider the latest suburban outbreak over.
The Daily Herald spoke with Illinois Department of Public Health Director Nirav Shah before a 15th case was found in suburban Cook County Wednesday. It's unclear whether the latest case is connected to KinderCare in Palatine, where 12 infants were infected with measles.
Shah talked about the potential end of the outbreak and how the department tracks the spread of the disease from its patient zero or "index case" to the other people who get infected. His answers are edited for length and clarity.
Q. There was just one new case in the last week, so is the outbreak nearly over?
A. That is definitely good news, however we cannot conclude anything just based on that decline or that slowing. Predicting the course of an epidemic, and particularly predicting when an epidemic might end, is like trying to predict what way the wind is going to blow at 7:30 tonight. You might get it right, but it's probably because of luck. We remain vigilant. We remain on the lookout and on alert.
Q. When will you be more comfortable that it's over?
A. We are still probably a good three weeks away from being, as you said, more comfortable in being a little more hopeful that the epidemic is in its dying stages. Nevertheless, it can always pop back up from a second index case.
Q. If we go 10 days without a case, then another one pops up, does that three-week clock start again?
A. Twenty-one days starts all over again. Even after the 21 days is over, most cases of measles in the United States occur because of what we call importation. That is a situation in which usually a U.S. person ... is marginally vaccinated or unvaccinated and visits a place in the world where measles is endemic. And when they return back home to the U.S., they bring it back with them. And so it could be in four weeks from now, well after the 21-day period, we could have another case.
Q. Why is important to track the first case?
A. What we're more concerned and focused on is determining the downstream activity, that it is to say to whom might this index case have transmitted the disease. By determining where the index case traveled, who they came into contact with, we can track the spread of the disease and ultimately dampen and control the outbreak itself.
Q. So you mostly need to know where that first case went more than where that first suburban patient got measles?
A. We are still puzzled and interested in determining where this individual could have contracted it, but we remain equally focused on determining who they could have spread it to. That involves starting with the index case and essentially creating a spatial map of each and every person that they could have come in contact with. I can tell you it's outrageously challenging in practice.
Q. How do you do it?
A. Every creative trick in the book, we use it. I've been involved with outbreaks many, many times in my career. Think about yourself. It's only 10 o'clock in the morning, but think about all the people that you could have potentially come into contact with today. People on the train. People at Starbucks. People anywhere in your office already, if you dropped your kids off at school. All of those places. So we start by tracing someone's steps. Literally, where have you been? Everywhere in the past three days, seven days, nine days, depending on the incubation period. And we go back to those instances and start putting people on alert. We start with the grocery stores they may have gone to. Movie theater they may have visited.
Q. So in this case, did you reach out to all the KinderCare parents?
A. Absolutely. We have reached out to parents, family members, people who have might have been in play groups. Absolutely, every one of those options.
Q. Is there any connection between the suburban outbreak and the one tied to Disneyland?
A. We don't have any evidence that it was directly tied to the California outbreak. But the thing with measles is that it is so incredibly contagious, that you could have sat next to someone on the bus whose wife was sitting next to someone on the plane from L.A. to Chicago, and that's how it could have spread. That makes the process of figuring out where you got it from very, very difficult, especially as we get further and further in time and geography from the California situation. Measles does and has occurred in Illinois to some degree over the past years, so this index case in Illinois could be related by some tenuous link. It could not be related.
Q. Are the KinderCare cases connected to the single case that came up at Elgin Community College?
A. I can't comment on the specific connection there.
Q. Does it concern you when the disease leaves a particular social circle like that?
A. Absolutely. It's the first concerning sign that an outbreak may be spreading. Fortunately, we were able to identify the individual associated with Elgin and the community college and ensure that that individual did not spread the measles disease further.
Q. ECC offered vaccine boosters after a case was identified there. Does that help immediately?
A. Once a patient is identified, there are a number of things we can do. One of them is to give folks boosters. It's not 100 percent necessary because nowadays, we're thankful that in Illinois, most folks are vaccinated. Nevertheless, the booster is readily available. There are virtually zero side effects to it. So out of an abundance of caution, the county health department in conjunction with our agency decided to offer the vaccine.
Q. Can measles be fatal?
A. As a result of the fact that in the past 60 years, we've been able to diagnose it better and we've been better at providing supportive care, it is something of a triumph to say that measles isn't a uniformly fatal disease. But that's in the United States. Worldwide, measles is tremendously serious and is actually a major cause of childhood mortality all around the world. Measles is a serious disease.
Q. Any other key points you'd like to make?
A. Vaccines. This is not a battle in which we are without weapons. We are fortunate to have a vaccine for measles that is outrageously effective and nearly 100 percent safe. It is as close to a perfect vaccine as we have in the world. Please get your kids vaccinated. Please get yourselves vaccinated if you haven't been.