CDC Telebriefing Transcript

Salmonella Outbreak Among Participants at the 2002 Transplant Games and West Nile Virus Update

August 8, 2002

CDC MODERATOR: Hi. Welcome to today's telebriefing. Today's briefing will feature two speakers, Dr. Padmini Srikantiah, and also Dr. Lyle Petersen.

We'll begin with the briefing with the update on the article, the outbreak of Salmonella Javiana, and Dr. Srikantiah will be our speaker for that portion of the briefing.

Before we start, let me spell her name for you. Her first name, Padmini, is P as in Paul, a-d as in David, m-i-n-i. Her last name, Srikantiah, is S-r-i-k-a-n-t-i-a-h.

Dr. Srikantiah.

DR. SRIKANTIAH: Good morning.

Let me just briefly provide a summary.

On July 16th, two cases of Salmonella Serotype Javiana infection were identified among persons who had attended the 2002 U.S. Transplant Games which was held at a theme park in Orlando, Florida, between June 25th and June 29th.

The Transplant Games is an athletic competition that was attended by approximately 6,000 people, including 1500 transplant recipient athletes. Transplant recipients were solid organ transplant recipients and bone marrow transplant recipients.

The results of an ongoing investigation have identified 141 illnesses in 32 states among persons who attended the games. The preliminary findings of the investigation have implicated diced Roma tomatoes supplied to the theme park as the likely vehicle for this outbreak.

Physicians should consider salmonellosis among ill transplant patients who attended the Transplant Games, particularly because persons with impaired immune systems are at increased risk of severe infections.

CDC MODERATOR: Thank you, Dr. Srikantiah.

John, at this time we'll now take questions.

AT&T MODERATOR: Thank you, and ladies and gentlemen, once again, if you do have a question at this time please press the one, and our first questions are from the line of Adam Marcus with HealthSouth. Please go ahead.

QUESTION: Hi. I have two questions, please. The first is how many athletes were sickened and how many attendees--I think I saw that there were some people who were just visiting the theme park but not necessarily attending the games.

And also there's an increased risk of salmonellosis in transplant patients. Did that make it more difficult to determine whether this was a result of the food poisoning as opposed to just the sort of baseline background risk?

DR. SRIKANTIAH: Okay. Thank you for your question. I'll start with the first question.

We've determined through our Web-based survey investigation, that there were 141 illnesses among Transplant Games attendees. Forty-eight of these--of the people who responded to the survey, 82 persons were ill and we took only one respondent from each household and collected detailed information.

So of the 369 persons who responded to this survey 82 were ill. Forty-eight or 59 percent of these patients were transplant recipients.

We have so far identified twelve people who have Javiana infection, Salmonella Javiana infection with, that matches this outbreak strain of Salmonella Javiana, and these twelve people did not attend the Transplant Games but did visit the theme park.

QUESTION: But the question I asked was how many were athletes?

DR. SRIKANTIAH: I don't have information of exactly how many of the transplant recipients who are will were also athletes. Only transplant recipients were athletes at the Transplant games.

CDC MODERATOR: Okay. Is there another question for Dr. Srikantiah?

AT&T MODERATOR: Yes. We do have a question from the line of Christian Weiss [ph] at the Associated Press. Please go ahead.

QUESTION: My question is which theme park?

DR. SRIKANTIAH: Our focus is not on the theme park but, rather, to focus the investigation on finding the vehicle that caused illness as well as making sure that persons who are caring for transplant recipients, patients, are aware of this possible exposure among those who attended the Transplant Games.

QUESTION: Okay, and a follow-up would be has anything changed at the theme park where the food was served? Instead of Roma tomatoes. Are they still serving that? Some of the people who got sick weren't, you know, connected at all with the transplant athletes, so--

DR. SRIKANTIAH: Right.

QUESTION: --what's been changed?

DR. SRIKANTIAH: The last date of illness onset that we have is July 8th. We have no information at this time to suggest that there is ongoing infection or ongoing--there are ongoing infections. The theme park has been very cooperative and has made changes to their menu.

QUESTION: Okay. But you can't talk about what those changes are?

DR. SRIKANTIAH: I think that that would be a question better--

QUESTION: Okay. Thanks a lot.

CDC MODERATOR: Is there another question for Dr. Srikantiah?

AT&T MODERATOR: Yes. We do have a follow-up from Adam Marcus. Please go ahead.

QUESTION: Yes. I was inquiring about the background rate of salmonella infection in transplant patients and whether that complicated the investigation.

DR. SRIKANTIAH: There's no evidence to suggest that persons who are transplant recipients are chronically infected with salmonella. The more important thing to remember is that persons who are transplant recipients are often, and quite often on anti-rejection therapy or immunosuppressive therapy, and this places them in the category of persons with impaired immune systems.

These persons at are increased risk for more severe illness if they become infected with salmonella, and an increased risk for complications of infection.

These complications may only present weeks to even sometimes months after the initial exposure, and as you may have noted from the article persons with, who are transplant recipients may also be at increased risk for relapse of infection.

CDC MODERATOR: Thank you. Is there another question on the salmonella outbreak?

AT&T MODERATOR: Yes, from Tom Watkins, CNN. Please go ahead.

QUESTION: Hi. How seriously ill did they become and did they all recover?

DR. SRIKANTIAH: Well, of course we don't have information on everybody who became ill. Those who responded to our survey, among the 82 who responded to the survey who are ill, only three had been hospitalized. Of course this is a skewed number since we only have a fraction of those who are ill who responded to the survey.

So that's the data that we're working with right now but--

QUESTION: Have they all recovered?

DR. SRIKANTIAH: We certainly know that there were no deaths, and we do know that among those who responded to the survey, they did not report any ongoing infection at this time.

CDC MODERATOR: Thank you. Is there another question?

AT&T MODERATOR: Yes, from Anita Manning with USA Today. Please go ahead.

QUESTION: Hi. Can you tell me how common this particular strain of salmonella is, and is it treatable, I mean, does it respond to medication?

DR. SRIKANTIAH: That's an excellent question. There are approximately 2,500 different serotypes or strains of salmonella. Salmonella serotype Javiana is the fifth most commonly isolated salmonella in the United States. Although it does not account for--it only accounts for approximately 3.5 percent of the isolates that we hear about at CDC.

There is no evidence to suggest that Salmonella Javiana causes more or less severe illness than any other strains of salmonella, and the strain of salmonella in this outbreak is susceptible to many commonly-used antibiotics, and those persons who have intact immune systems often do not need any antibiotic therapy and recover in a matter of a few days without antibiotic therapy.

Those who have impaired immune systems definitely may benefit from antibiotic therapy.

CDC MODERATOR: Thank you. Is there another question for Dr. Srikantiah?

AT&T MODERATOR: No further questions.

CDC MODERATOR: All right. Then we'll move on to the next part on our telebriefing, the West Nile activity in the U.S., and Louisiana, and again that's Dr. Lyle Petersen.

Before we begin, though, please make a note of the spelling of Dr. Petersen's last name. It's P as in Paul, e-t-e-r-s-e-n.

Dr. Petersen.

DR. PETERSEN: Good morning or good afternoon, depending on where you are.

CDC and state and local health departments continue to monitor the spread of the West Nile throughout the United States. The current case count, as you can see from the MMWR, as of yesterday afternoon, was 112 cases with five deaths, with cases noted in Louisiana, Mississippi, Texas, and Illinois.

These cases are monitored through a system called ARBOnet which I'll describe right now. ARBOnet is a realtime electronic reporting system developed by CDC and local and state health departments, and operated throughout the year.

The surveillance system is present in the entire continental United States, as well as the State of Hawaii. The surveillance system monitors the spread of West Nile Virus infection in birds, mosquitoes, humans, horses and other animals.

One thing we have found with this ArboNET system is that with the dead bird reporting system, we found it to be an extremely sensitive measure of the spread of the West Nile Virus in nature, and thus it is the source of much of the data that you see here on the map in the MMWR.

Obviously, the cases in Louisiana, Texas and Mississippi have received a lot of attention because of the sheer number of cases that have occurred so early in the transmission season. Because of this, CDC has a number of ongoing studies, ongoing in Louisiana. These include our personnel there are currently doing five main activities.

One is we are cooperating with the State of Louisiana to do an intensive search for cases in that State.

The second thing we are doing is we have investigators there trapping mosquitoes to see which types of mosquitoes are carrying the virus and which are the most likely to spread the virus to humans.

The third thing we are doing is that we have a live bird study where we are trapping, and bleeding and releasing live birds to see how many birds are actually becoming infected with the virus in that area and what species of birds may be becoming infected, to what extent.

The fourth activity is a clinical study, where we're examining the clinical presentations of patients presenting with severe neurological disease as identified through our surveillance system.

And the last major activity there is we are actively searching for patients with West Nile fever; that is, the mild form of the West Nile Virus infection. Those that have West Nile Virus infection develop some flu-like symptoms, but don't go on to develop encephalitis or meningitis.

With that, I will conclude.

CDC MODERATOR: John, we are now ready for questions for Dr. Peterson.

AT&T OPERATOR: Thank you. Once again, ladies and gentlemen, if you do have a question, please press the one.

We have a question from Victoria Elliott with the American Medical News. Please go ahead.

QUESTION: Since the U.S. hasn't really had a problem with mosquito-borne illnesses for decades, I was wondering why all of a sudden this is now a problem in the past few years. Did we just get really complacent?

DR. PETERSON: Well, there's a little bit of both. Your statement is actually half true.

QUESTION: Okay.

DR. PETERSON: The major scourges of the vector-borne diseases, scourges of the United States were largely eliminated several decades ago, which include yellow fever and malaria and, to some extent, dengue.

However, there is a related virus in the United States called the St. Louis Encephalitis Virus which has caused a number of outbreaks over the years. There was an outbreak in the mid-1970s of St. Louis Encephalitis Virus which caused well over a thousand cases of severe neurological disease. And because this virus is similar to that of the West Nile Virus, we obviously have taken that into close account.

Epidemics of St. Louis Encephalitis Virus have also occurred in 1990 in Florida with several hundred cases, as well as in Wachita Parish in Louisiana just last year, in which there were--I don't know the exact number--but between 60 and 70 cases of severe neurological disease.

In addition, there are a number of other mosquito-borne diseases that are of concern in the United States. Eastern Equine Encephalitis only causes a handful of cases per year, but it has a very high rate of morbidity and death in very young children. California Encephalitis-type virus, otherwise known as Lacrosse Encephalitis Virus, has had increasing activity in the mid-Atlantic states--Tennessee, Kentucky, the Carolinas--in recent years.

So these vector-borne diseases have been present over time. It's just that West Nile Virus activity has brought it to the forefront.

CDC MODERATOR: Thank you. We are ready for our next question, please.

AT&T OPERATOR: And that is from Tom Watkins, CNN. Please go ahead.

QUESTION: Can you describe how many CDC people are in Louisiana and just, they are all working on these five things?

DR. PETERSON: Yes. There are currently about 20 people in the field at the present time. The number varies slightly from day-to-day as people come and go, as they start and finish their activities there. They are working in these five activities.

CDC MODERATOR: Next question, please.

AT&T OPERATOR: That is from Lee Hopper, Houston Chronicle. Please go ahead.

QUESTION: Hi. Do you have any information about underlying health conditions of the Louisiana cases? That seems especially pertinent in a lot of the--number of the younger victims.

DR. PETERSON: Right. Through ArboNET, we do not collect information about the underlying health conditions of these patients. It is certainly something we are looking at as we look at these cases in more detail, but the full results of that will not obviously be completed for many months.

What we do know from previous experience here in the United States is that the single most predominant risk factor for developing severe neurological disease after infection is age greater than 50, and it will probably continue to be so as the people in Louisiana, Texas and Mississippi and the data are fully analyzed.

Other predictors that--other independent risk factors that may be present would be the presence of diabetes and immunosuppression, but the previous data on that are inconclusive.

CDC MODERATOR: Thank you for your questions.

We are ready for our next question, John.

AT&T OPERATOR: That's Deidre Henderson with the Denver Post. Please go ahead.

QUESTION: Good morning, Dr. Peterson.

What do you make of the theory that record-high temperatures have shortened mosquito incubation period and generation time and may be a factor in the spread of West Nile expansion?

DR. PETERSON: Well, first of all, it is a theory. One of the things that people try and do with these what we call Arboviral or mosquito-borne infections, is people try and simplify all of the factors that are involved in what causes an epidemic or what doesn't cause an epidemic in a certain area. There are many factors which influence both the mosquitoes and the primary hosts--birds--which influence these cycles in nature.

Now, if you look at severe West Nile Virus outbreaks in recent years in Romania, Russia, New York City, and Israel, they seem to be accompanied by very warm, dry summers, so there may be a common factor there, but there are other factors which probably influence these cycles to a great degree also.

The reason why warm weather seems to promote these outbreaks are probably multiple. One could be that in warm weather the--in fact, it has been shown that in warmer weather the generation time of the virus in the mosquito is shortened. Thus, mosquitoes get a higher viremia in a shortened period of time. However, when the weather gets too hot, mosquitoes begin to die. So it's a complicated cycle.

Hot weather also probably affects the mosquitoes by affecting their breeding areas. The kinds of mosquitoes that transmit West Nile Virus like to breed in very small murky pools of water and during hot weather larger pools sort of condense into smaller pools with concentrated organic materials which make ideal breeding sites for mosquitos.

So the short answer to--my long answer to your short question is there's probably a lot of factors involved in this, but warm weather seems to promote these kinds of outbreaks.

CDC MODERATOR: Next question, please.

AT&T MODERATOR: And that's from Cory Locke [ph], U.S. News & World Report. Please go ahead.

QUESTION: Hi. I have two questions. The median age for the cases is 55 years. Is that lower than in years past? 

And second question. When was ARBOnet started and how long have all 50 states been monitoring for West Nile?

DR. PETERSEN: ARBOnet was started in 2000, the following year, after the 1999 outbreak, and was in place in the upper Eastern half of the United States. Subsequently, over the years, we expanded ARBOnet to the Eastern half of the United States and this year to the entire country.

Regarding the median age of 55 years, I don't know why the median age--actually, the median age of 55 years is in fact younger than the median in previous years, which was about in the mid '60s.

The reason why patients, these patients this year seem to be younger is unknown and it's certainly something that we're actively looking into.

CDC MODERATOR: Next question, please.

DR. PETERSEN: And that's from Marian Marshion [ph] with the Milwaukee Journal. Please go ahead.

QUESTION: Hi, Dr. Petersen. I noticed you didn't mention anything about human sero surveys to try to determine exposure rates and I have two questions.

Have any sero surveys been done since those in the fall of 2000 in the New York/Connecticut area?, and, secondly, what is known or believed about whether previous exposure to the virus confers any immunity to serious disease?

DR. PETERSEN: Let me answer your first question about sero surveys. We have conducted four sero surveys, here, in the United States, three during 2000 in the New York/Connecticut area, and one in 1999 in Queens, New York, in the epicenter of the outbreak.

In addition, we've conducted a sero survey in Romania during their outbreak in the mid 1990's, and the reason we're not doing another one is that the results of all these sero surveys are extremely consistent, and that is about one in 150 people develop severe neurological disease.

And so if we get a sero survey in Louisiana or Texas, or Mississippi, we're likely to find the same results.

So we just don't see a need to do a sero survey. It takes a great amount of resources to do that, and we think the higher priorities are the activities that we're currently doing right now.

Now the second question was about previous immunity. We think that previous exposure to the West Nile virus would in fact cause somebody to be immune to the virus. This is based on data from other Flaviviruses, from Flaviviral infections.

West Nile virus is a Flavivirus, and if you look at related viruses like St. Louis encephalitis virus, yellow fever, dengue, Japanese encephalitis virus, when somebody's exposed to one of these viruses they don't get them again, with one exception, and that is dengue, and that's because there's four types of the dengue virus.

CDC MODERATOR: Thank you. John, we have time for one more question.

AT&T MODERATOR: And that'll be from the line of Christine Wyatt [ph], Associated Press. Please go ahead.

QUESTION: Yesterday, you talked about the median age being lower than in years past. Also this morning you said 60 percent of the cases you found were in men. Is this in line with what you found before or is this new?

DR. PETERSEN: There seems to be a slight predominance of cases among men. We've observed this every year. 

We don't know whether this is due to just that men may have a greater exposure to mosquitos or whether there's some inherent differences between men and women, or even whether these results will hold out to be statistically significant over time.

CDC MODERATOR: Thank you ladies and gentlemen for your participation in today's telebriefing.

If you have additional questions about Salmonella Javiana or West Nile virus, you can give us a call at 404 639-3286. Also the transcript from today's telebriefing will be posted to the CDC media relations Web site later this afternoon.

AT&T MODERATOR: And ladies and gentlemen, that does conclude your conference for today. Thank you for your participation and you may now disconnect.

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