Mumps Outbreak 2006
According to the CDC, the multi-state outbreak of mumps in 2006 resulted in 6584 cases of mumps. Most of those affected were Midwestern college students living in dormitories.
As Dr. Gerberding points out in her press conference (see transcript below): "Fortunately, [mumps] is usually not a serious disease" and complications are "rare."
Good afternoon. Thank you for taking time to join us for this press conference on mumps. We know that there is a large outbreak of mumps going on mainly in the Midwestern part of our country, and this has been a tough time for college students and their parents and the people who are responsible for containing this problem. This actually is the largest outbreak of mumps that we have seen in this country in more than 20 years. We have more than a thousand cases reported from eight states, and we also have additional cases undergoing investigation in seven more states. We are not going to be surprised if there are more cases in more states just given the nature of mumps and the way this outbreak is progressing.
I really want to take a moment to thank the public health officials in the affected states, including Iowa that has been the hardest hit. These individuals have been working tirelessly to try to ascertain the source of the outbreak, work hard to take the steps to contain it, and also working very, very hard to provide information and updates on an ongoing basis, all in a very fast track. So we really applaud and appreciate, as always, our colleagues in the state and local public health systems.
We would like to just say a couple of things about mumps just for people who are not familiar with it. Fortunately, most people are not familiar with mumps because we have had a vaccine since 1967 and that vaccine has largely eliminated frequent outbreaks of mumps in our country. Mumps is a virus disease. It generally affects the body with fever, headache, and tiredness, the kinds of virus-like illness that we get with most of the common viruses. But it has a very special tendency to cause inflammation in your saliva glands, so people get the big, puffed cheeks from the involvement of those glands.
Fortunately, it is usually not a serious disease. People are usually ill for a week or so. But, in some people, it can have serious complications. Up to 10 percent of people will develop meningitis, a certain proportion of people will develop orchitis, that's an inflammation of the testes, which in adolescent boys or older men can sometimes lead to infertility. It can also involve other tissues. It has been reported to be associated with spontaneous abortion and potentially deafness. So although these complications are very rare, occasionally they are serious and our understanding is right now there have been at least 20 hospitalizations associated with this outbreak, but, fortunately, so far no deaths.
I have to emphasize that the best protection against mumps is the vaccine. There is a lot of confusion right now about whether or not this outbreak is related to some problem with the vaccine, and I really want to emphasize that while we are of course investigating the outbreak and we will learn more about the efficacy of the vaccine in this particular setting, we have absolutely no information to suggest that there is any problem with the vaccine.
The problem here is with the lack of complete coverage of the vaccine, number one. Our vaccine program for mumps began in 1967, but just by nature, there is a group of students, roughly college-age students, who may be less likely to have received both doses of the mumps vaccine and are incompletely vaccinated. Therefore, they are susceptible when infection is introduced, and they have a very high chance of getting mumps under those environments.
In addition, although this is a very good vaccine, it is not perfect. About 10 percent of people who get both doses of the vaccine still remain [susceptible] to mumps. So if you are in a community of 10,000 people and 10 percent of the people who got both doses of the vaccine are susceptible, once you get a little outbreak going in that community, that means that up to 1,000 people in the community would actually come down with mumps even though they were properly immunized with what we know is a very good vaccine.
What is going on here in the context of the outbreaks is a number of people who have not received both doses, coupled together with people who have received the vaccine but are susceptible anyway because it is not perfect, living in crowded conditions like college dormitories, or mixing up with other students such as might happen during spring break or the holidays, and really setting off a cascade of transmissions that is going to take a while to curtail and eventually stop. The most important step that is being taken in the affected areas is to implement vaccine programs for those people who have not received both doses. For individuals who are in the school age population, for individuals who are post-high school in the school environment such universities or colleges, or people in institutions, and very importantly, for health-care workers, if you have not received two doses of the mumps vaccine, it is very important that you get your second dose. The state health officials in the affected areas are working hard to develop plans and to support the access to the school in this context.
CDC is taking some steps to support the states. We do have disease detectives who are working on assisting and helping to study some of the features of the outbreak so we have a better idea and can learn from this as the virus spreads from community to community. We are also assisting in the supply of vaccine itself. We are very pleased that we have some mumps vaccine in the form of mumps, measles, and rubella vaccine in our stockpile. Already we have committed to make 25,000 doses of that vaccine available to the state of Iowa to support them as they need it. But in addition, I am very pleased to say that Merck, the company that makes MMR II has donated to CDC, 25,000 doses of vaccine that we will use as we see fit to help support to immunize people in the affected areas. It is a very generous gift, and we are happy to have it because this outbreak is happening somewhat late in our fiscal year and we appreciate the opportunity to have an additional supply to share with those who need it. The vaccine really is the best protection. We again emphasize the importance of getting both doses of the vaccine.
What we expect to happen in the next several weeks is that immunization will increase. The medical community has received information and resources from CDC and from state health officials. A lot of clinicians have never seen a case of mumps, and so we have to remind and refresh them about what mumps looks like. Sometimes mumps is not very symptomatic, and not everyone gets the swollen glands, so it can be confused with other viral illness. Fortunately, our laboratories at the state health department level have the special test necessary to rapidly diagnose mumps, so they are playing a very key role in this investigation. We are encouraging clinicians who have any suspicion about cases to check with their local health officials to make sure that they are doing everything they need to do to ascertain whether a case exists or not. But we will not be surprised if we see more people affected either in the college context or as students who spend time with their families or with their community friends, we will continue to see some extension of this outbreak into the community level and we need to be prepared for that, and if things change or if the pattern changes beyond what we expect, certainly you can look forward to further updates from CDC as well as further updates from health officials at the local level who are really on the front line of this and who are in the best position to be able to advise the community about what specifically should be done in their community.
Let me stop now and take some questions. I'll take one from the room first.
There are several different methods for determining vaccine efficacy, but when we have cases of mumps, the first question to ask is, is this person not vaccinated, have they had one dose of vaccine or do they have two doses of vaccine? One thing we can do is compare people with mumps to people like them who did not have mumps, and by comparing the frequency of vaccination in the people who have the disease with people who do not have the disease, we have tools that allow us to estimate vaccine efficacy in that context. So that really is the simplest way, and those are the kinds of things that our teams are looking at with the state health officials in the field as we speak.
The question is do we have initial results, no, and you can expect that as this is an unfolding story, that will take some time. One of the complications is that most people do not have electronic health records, and so ascertaining vaccine status particularly from childhood vaccines, is something that we do not have rapid tools to accomplish right now. Until we have electronic health records, we are going to have to do this the old-fashioned way, by mom's recall sometimes, and by searching through hard copies of medical records which are difficult to get one's hands on. So expect this to take a bit of time, but right now we are not seeing anything surprising in this pattern of transmission that would suggest that there is a vaccine problem, per se, it is a problem of complete coverage of the vaccine and the fact that even when the vaccine is optimal, it is never 100-percent protective.
I will take a telephone question, please.
Thank you, Doctor. Nicole Aksamit with Omaha World Herald, your line is now open.
Dr. Gerberding, in Iowa we know the largest age group affected is roughly between the ages of 18 and 22. From the data that Iowa has presented, it indicates that that is whether or not those people attend college and whether or not they were indeed vaccinated once or twice. We have not seen that particular age population being a spike in the cases so far in Nebraska, and I guess I have not seen age breakdowns in the other states that have cases.
Could you address whether that has been uniform across the board, that there is a spike in college-age people? And if not, what is the running theory on why that age group in Iowa?
The main reason that college-age people were particularly involved I think early in Iowa is that they are very crowded together and somewhere along the line there was a college campus where someone came down with mumps and it began to spread in the social context of that campus. But you have to think of this as a network, and so when someone leaves the original source of an outbreak and goes to a new community where there are susceptible people, whoever those people are or however old they are, they will be the next to come in contact with the mumps virus. So this is the kind of work that the state health officials are engaged in right now, tracking down the who, what, when, where, why, and how of the outbreak, and we can expect there will be lots of variations on a theme as this work gets conducted.
I will take another phone question.
Thank you. Anita Manning from USA Today, your line is now open.
Thank you very much. Dr.Gerberding, I am sorry, but I could not hear the first question that you were asked from the room, and I think it had to do with a waning immunity question. If you do not mind, we have seen waning immunity with other vaccines like the pertussis vaccine, and I was just wondering if there is any kind of blood testing or serologic testing going on in the communities there to see if there is a waning immunity.
Then a second question that I have is, is there any evidence that this is spreading by people who are asymptomatic? Is there asymptomatic spreading? Thank you.
In terms of waning immunity, we have no evidence from any of the information we have so far or from historical experience that waning immunity plays any part. People who receive two doses of mumps vaccine just sometimes simply do not respond to it. Their immunologic system just does not regard that as a source of stimulation to their immune system. If waning immunity were a primary problem, we would expect much older people to be affected, at least those who did not have mumps when they were children. So we are looking into this as one of several possibilities, but I think right now what we know about this vaccine's efficacy, what we know about the undervaccinated people in this age cohort, and what we know about the sociology of life in some of these community settings, we have ample explanation for why the virus is spreading the way it is.
It is possible for asymptomatic people to transmit mumps virus. People are sometimes asymptomatic for a significant period of time, and about 20 percent of the time, the cases are mild or asymptomatic, so the disease can be transmitted in the context of a person who does not recognize that they have mumps, all the more reason, again, for people who have not received both doses to get their vaccines.
Also, people who are going to have symptomatic mumps are sometimes able to transmit the virus for 2 or 3 days before they actually have it. So there are several reasons why it is sometimes difficult to completely immediately contain the problem because of the asymptomatic nature of the spread.
One of the other important aspects of containment in addition to the vaccine is that people who do have mumps should remain isolated during their period of contiguousness. This is very important, so that they are not out and about, and particularly college campuses, that they are not exposing other students, or if they are health-care workers, they are not exposing other health-care workers or patients. So it is important to follow the local health official's advice about isolate the people who are suspected or known to have mumps.
I can take another telephone question, please.
Thank you. Rob Stein from the Washington Post, your line is now open.
MR. STEIN: Thanks very much for doing this. I have a couple of questions. The first one was that you said 1,000 cases in eight states. I was wondering if you could give us the breakdown on how many of those are in Iowa and how many of those are in the other states, and what those other states are.
Then the thing is, is the outbreak continuing at the same rate? Is it slowing down? Is it accelerating? Do you have any sense of where things stand in getting it contained?
I do not think this outbreak is at steady state, so we can expect some variability and some stuttering as it moves forward. There are 815 reported cases in Iowa, at least as of our last communication with the Iowa State Health Department, so that by far is the largest number of cases that we are aware of so far.
There are 350 cases reported from seven other states, which includes Minnesota, Kansas, Illinois, Nebraska, Wisconsin, Missouri, and Oklahoma, and if you did not get that, we can circle back to you with that information. Then there are a handful of other states that may have cases, but they just have not confirmed them as probable or definite cases and so they are still a work in progress.
The epidemiology or the characteristics of the cases in all of these areas is still undergoing an active investigation. As I said, many clinicians have not been familiar with mumps because they have not really seen cases in recent years, so part of this is as clinicians become more familiar or more aware of what we are looking for, we would expect to see more cases just because there are more cases being diagnosed. So a work in progress, and we will try to provide updated information on this as states make their reported cases available to CDC. Other questions here?
[Off mike] outbreak, what should people be doing as far as protecting themselves? Should they be seeking the vaccine, and is there enough vaccine if people go out and try to get those second doses in [off mike]
CDC has sent a health alert to the health officials and clinicians reminding people that generically it is important to encourage second-dose vaccinations for those people who do not have it. Fortunately, because we have such high coverage rates among younger children for vaccines, most children in our country actually have received both doses of the mumps vaccine. Older people have had mumps, we just have this transition zone going on where there will be significant numbers of people, and we do not know exactly what proportion of people in this age group have not received both doses. That is another one of the estimates. It is probably not constant from area or population to population.
We have significant numbers of doses in two of the CDC stockpiles, in a stockpile called Vaccines for Children. That vaccine can be used for kids up to 18 years of age. We also have stockpiled vaccine in our 317 Vaccine Stockpile which can be used for emergencies for whomever needs it, and we will not hesitate to use the vaccine that we have stockpiled as we need it, and if we need more, we can ask for flexibility in the use of what we have, and also the manufacturers of it have indicated cooperation, as Merck demonstrated by its donation today. So right now we are not anticipating in the short-run a vaccine shortage problem, but, of course, as this expands and goes on, we will keep you updated as the supply and demand issues unfold.
Another question from the phone?
Thank you. Karen Shideler with the Wichita Eagle, your line is now open.
Thanks for your help today. I have two quick questions. Number one, you mentioned older people who have had the mumps. I know that is not the case because in our news room there have been several who have come up and asked, Should I go get the shot now. My second part of that question is, is there a way to tell whether or not you are in the 10 percent of who the vaccine did not take?
Right now there is not an easy test for determining whether or not if you have had the vaccine, you are susceptible. There is an antibody test for mumps, but the relationship between that test result and susceptibility is not completely ascertained. There is a lot of science that needs to be done in looking at that particular measure, and it is not something that is clinically useful or available to people at this point in time.
For people who have had mumps, it is important to remember that we assume that you are now completely protected against mumps, so having had mumps as a child is in this context a safeguard against an additional case. It would be unusual for someone to get mumps twice, it has probably happened, but it would not be a concern in the context of the outbreak that we are experiencing.
It is, again, just so important to emphasize that one of the lessons learned about this particular outbreak is that vaccine coverage matters especially when we are dealing with a vaccine that isn’t 100-percent efficacious, that even a slight reduction in the coverage that we could achieve can create an environment where it is even more likely for the mumps virus to spread. So fortunately we are not seeing outbreaks right now in schools or in younger children in large part because they have a higher degree of two-dose coverage. That does not mean it could not happen, because there will be children in school, of course, who have not completely responded to the vaccine. But it just a reminder of what happens when we have any lag in our immunization coverage for people.
Is this outbreak connected to the one in the United Kingdom?
We do not know yet about the relationship of how this virus got introduced. In past outbreaks of mumps, there was a very large outbreak of mumps in the United Kingdom. They are particularly related, again, both to the vaccine efficacy, but also the much lower coverage rates in the population, so they had more than 100,000 cases of mumps in a country that is much smaller than the United States, and that is a very sobering reminder of why vaccine coverage matters.
We do know that the genotype at least in the early cases of this outbreak was the same genotype of virus that was associated with the United Kingdom outbreak, but that does not necessarily mean there was a direct link to introduction. It is certainly possible, but we do not have any proof of that at this point in time.
I will take another phone question, please.
Thank you, Jeremy Manier from the Chicago Tribune, your line is now open.
Thanks very much. I do not mean to downplay what you said about the importance of vaccine coverage, but in this case, I wonder if it is really applicable to this outbreak. The figures that Iowa has released so far anyway are that only 3 percent of the people they have studied had no dose of the vaccine at all, and 65 percent they think had two doses. I am not saying that that does not play a role, but in this I am not sure how it comes into play.
Also, the second part of this, are you concerned that the problem here could get to the same kind of scale as the U.K. has seen? What would it take for this to become something that evolved into tens of thousands of cases over a period of years as they have?
As I said, this is an unstable situation right now and we are not able to reliably predict where this will go. We do know what is important about containment, and we are doing everything we can to support the state health officials who are responsible for executing those steps. I do not want to second-guess the specific elements of the containment and preparation activities that are ongoing in the state because every jurisdiction does have a little bit different epidemiology and a little bit different problem to solve. We do expect more cases, absolutely. We hope that the steps taken to isolate infected people as well as vaccinate to raise the general level of protection will definitely help slow this down. We have seen that successfully work in the past, and we hope that it would be successful this time.
In any population, your question about the importance of undervaccinated people, it is a function of how many undervaccinated people there are, if the people who have only received are only 65 or 80 percent protected, then obviously if the mumps virus is introduced and there are a lot of those people, it is going to take off much faster and there will be a very vulnerable group of people versus a smaller percentage of people who are vulnerable because the vaccine was not working, but a small percentage of large number of people is still a lot of susceptibles. So if you have 100,000 people and 10 percent of them did not respond to the vaccine, that is still a very large proportion of people, and if that population is large compared to those who have only had one does, then you will see that the statistics represent the majority of cases being in the two-dose vaccinated population.
So we are seeing pretty much what our math would suggest, but some of them work that we are doing in these areas is to really dig into these numbers and try to understand the transmission dynamics with more precision, and I think we can give a better you a better answer to your question when those data become available.
I would ask if our mumps expert, Dr.Seward, would have anything to add to that. If you would just come up to the microphone, Jane. This individual is the world's treasure house of information on mumps, so she has been very busy lately.
I am Dr. Jane Seward, Division of Viral Diseases, CDC. The one information I would add is that the attack rates that we are seeing when we look at a very specific case definition for mumps was parotitis in these two-dose vaccinated colleges is quite low, and much, much lower than attack rates in high schools 20 years ago. So that would lead us to believe, again, that we are getting very good protection from the MMR vaccine. As Dr. Gerberding explained, the reason such a high proportion of cases have received two doses is because such a high proportion in the population have received two doses of MMR vaccine.
I will take another question from the phone, please.
Thank you. Tony Leys from The Des Moines Register, your line is now open.
Doctor, I would like you to compare the danger of this outbreak to previous outbreaks such as West Nile. Also, are you concerned that with the semester is going to be over in the next couple of weeks at a lot of these schools and kids will be going home, are you concerned that that is going to spread it across the country?
No, we have characterized this as a college-age population of students at risk. It is important to remember this is not just about college students. That just happens to be the largest and earliest hub of transmission that was recognized.
We have seen many opportunities for the first transmission environment to seed the virus into other communities, into families, and into other age groups. So as people went on their Spring Break, as they went for Passover or for Easter, students are highly connected as are most people these days, and so we really cannot predict at this point in time where the virus will go next and what other populations of people we need to be concerned about.
Let me emphasize again, however, that health-care workers are always going to be a special risk population for any communicable disease. It is very important that the health-care professionals who may be taking care of people of any age with mumps be sure to have both doses of the vaccine just to give them that extra oomph of safety.
The answer to your first question, I'm sorry, I forgot your first question, so you will have to repeat it for me.
The danger compared to West Nile.
The comparative risk of this mumps outbreak to other infectious diseases such as West Nile, no, it is really an apples and oranges kind of comparison. We are very early in understanding the scope and magnitude of this problem. We hope that we will soon get to the down slope of the curve, but we do not know that yet, and we just have to ultimately do everything possible to take the steps necessary for containment, and I think in retrospect we will be able to get a full picture of the magnitude of the problem.
One advantage that we are seeing at least so far in this outbreak is that most of the people are young and relatively healthy. We have not had any deaths so far related to this outbreak, so that is less morbidity and mortality than something like West Nile which tends to preferentially cause the most severe disease in the elderly, facilitates a much longer sequelae and sometimes much higher fatality rates. So it is an apples and oranges comparison, and I do not think that we can really say that one is less bad or more bad, but we certainly in all cases will do everything we can to try to contain them.
I am going to just take one more question from the phone, please.
Thank you. Brian Hartman with ABC News, your line is now open.
Thank you. Is there any doubt that you will eventually be able to contain this outbreak in fairly short order? And I also wonder if you could give us any detail on the seven states that are under investigation, but you have not confirmed anything.
Your second question about states, I am not going to discuss states that have not officially reported cases because it is really the province of the states to make the first steps toward identifying and reporting cases, so we are not going to reveal any information before they have been confident that they have accurate perspectives to share.
The whole issue of inability to contain it I think is to some extent a semantic issue. Mumps is not an unheard of disease even in the absence of an outbreak. We have mumps every year. We see cases from time to time. What is unique here is that we have a cycle of transmission that has resulted in a conspicuous outbreak and one that seems to be extending further and further across communities at risk. So we certainly will not see a complete end of mumps when this cycle is broken, but we do hope to reduce the ongoing, rapid transmission in the population that would best be characterized as an outbreak.
Thank you for your interest, and we do commit to giving you updates as more information becomes available. Thank you.
Thank you. This does conclude today'sconference call. We thank you for your participation. [End of press conference.]