SARS Home

CDC Telebriefing Transcript

CDC's Response to Reports of SARS

April 24, 2003

DR. GERBERDING: Good afternoon. I'm here to provide an update on SARS, the Severe Acute Respiratory Syndrome, and to follow up on some of the information that was presented in today's MMWR, the Morbidity and Mortality Weekly Report, that CDC has published.

The update, WHO is reporting 4,402 cases of SARS; 263 deaths in 26 countries overall.

In the United States, we are tabulating 247 cases of SARS, 39 of these are probable. There have been some of the SARS probable cases that have moved to the suspect list, and some on the suspect list have moved to the probable list. So there's been some exchange of individuals, but the total number of probables today is at 39.

Of those 39 cases, 37 occurred in travelers to parts of the world where SARS transmission is occurring, one occurred in a health care worker, and one was a household contact. There has been no change in the numbers attributable to spread from known SARS cases over the last 24 hours

We are continuing to prioritize the efforts made to contain this epidemic in the United States, and I want to review very quickly again what specifically those efforts are.

First and foremost, our efforts are targeting travelers to affected areas of the world. The parts of the world where there is ongoing, unlinked community transmission include Hong Kong, China, and Singapore, and currently we are still considering Vietnam in that category, although the situation in Hanoi looks like the transmission may have slowed down or stopped there. So we'll be keeping you up-to-date on the situation there as we get more information from in country.

So we are continuing to advise travelers not to go to those regions unless it is absolutely necessary. We are not including Toronto in the list of countries where travel restrictions are appropriate.

We are also alerting travelers who are going to Canada that there is SARS in that region and that they should be aware of that fact and take appropriate measures to avoid situations where transmission may be occurring, and right now that's primarily the health care settings in Toronto that are taking care of SARS patients.

Beyond that, we're urging all travelers to use common-sense measures to protect themselves from any infectious disease, and first among those measures is, of course, hand hygiene or careful washing with soap and water.

In addition to dealing with travelers who are going to countries where SARS may be an issue, we are continuing to alert travelers coming from those countries. We have passed out now more than 605,000 travel alerts to people returning from areas of Asia where SARS patients may be present. We will be initiating that alerting process for travelers coming to the United States from Canada toward the end of this week, and that will include not only the Toronto International Airport, which sends flights to more than 50 areas in the United States, but, in addition, four major and nine smaller border crossings between the U.S. and Canada and the Province of Ontario.

That effort is ongoing, but there are millions, and millions, and millions, I think something like 62 million travelers back and forth between Canada every year. So we are expecting that we'll be issuing a lot of alerts just to cover the large number of travelers that you commute back and forth.

We are not including Toronto in the advisory process, where we're looking at cases of SARS that are being transmitted in the community in an unlinked fashion, and the reason for that is because in Canada, while there have been cases where transmission has occurred outside of hospitals and close household contacts, we can link them all back to the index family that traveled from Hong Kong.

And so we can predict so far in Toronto where the patterns of transmission are leading us, and there is no evidence that travelers to that area are at any different risk of acquiring SARS than they are from going to any number of the other countries in the world where sporadic cases have cropped up among returning travelers.

Of course, we are working, in a very transparent way, with HealthCanada and the Canadian Government to exchange information and share information as we go forward, and as we learn more, if something changes in Canada, we will, of course, update our recommendations accordingly.

We are very pleased with the ongoing collaboration with the WHO in all of these matters, as well as the incredible collaboration that we have with HealthCanada and the health care community in Toronto. The CDC team is still in Toronto. They are there specifically to provide technical assistance around prevention of spread in the health care setting. This assistance includes our environmental engineer and some experts in infection containment under circumstances of airborne precautions.

But I think the most remarkable aspect of this entire SARS response has been the ongoing, high-caliber collaboration among all partners. We are learning a great deal from WHO, we are learning a great deal from HealthCanada. We are actually extremely fortunate here domestically to have this kind of information exchange, and it truly is helping us prepare ourselves for any situation where we would need to invoke stronger measures or more comprehensive measures at containment to protect citizens in the United States.

So my thanks and appreciation go to our partners both in the epidemiology and public health world, as well as the laboratory scientists who are supporting this investigation everywhere.

So let me take some questions here. We do have callers on the line. I'll give them a chance to get started, and I'll take my first question here from a reporter in the room.

QUESTION: Hi, Dr. Gerberding. Is there a difference in the way the CDC is identifying the cases versus WHO? Not to put you guys in the middle between Canada and the WHO, but how come you seem to have a closer identification to the ways Canada sees these cases versus WHO? Why has the U.S. not issued a travel advisory the way that WHO did?

DR. GERBERDING: Well, we're working with WHO to get more information about the basis for their decision, and there may be investigations under way that we don't have information on or additional facts to learn. But what we know right now is that the cases in Canada are linked primarily to hospitalized SARS patients. The vast majority of the problem in Canada has been among nosocomial spread or hospital spread of the infection. The involvement of the religious community was linked to a health care situation with an affected patient, and the subsequent spread during the religious meeting is explainable and understandable, and we can account for the patterns in that group.

That is the source of one probable cause patient in the United States. The patient was described in the Morbidity and Mortality Weekly Report today. That individual had attended the religious meeting, returned to the United States, became ill, was hospitalized. The health care workers who had unprotected exposure to the patient were evaluated. A total of 8 of them were put on voluntary furlough to be sure that they weren't incubating SARS, although that was a precaution. None of them have become ill with SARS at this point in time. And so there's been no subsequent transmission from that individual, at least to date.

But I think we understand the patterns of transmission in Toronto. They make sense. The epidemiologic picture is complete, and there's no suggestion that a traveler going to Toronto is inadvertently coming into contact with a SARs patient. If anything, the cases of concern, there have been individuals linked back to the health care setting or the index family and then have traveled outside of Toronto, then south. So that issue of exportation of SARS is a concern, but that is not a concern that a travel advisory will necessarily address. Travel advisories pertain to people going into the country.

So we certainly look forward to learning more about the unfolding situation, and are very respectful of the different perspectives that have come to light, but from the standpoint of protecting U.S. personnel and citizens, we think that the information we have right now is allowing us to continue with our current strategy, and if we need to change it, we will.

May I take a telephone question, please?

OPERATOR: And phone participants are reminded at this time to press the 1 on their phones if they wish to ask a question.

We do have a question from Joanne Silberner with NPR. Please go ahead.

QUESTION: Thank you. Dr. Gerberding, from MMWR, it looks like the last case in the U.S. was April 19th, and I gather there have been none since then. What's the meaning of that?

DR. GERBERDING: Well, you have to always remember that there is a lag between when cases are first recognized and the reports come to CDC. Even if a report is called in initially, we go through a pretty detailed process of filling in the blanks and making sure that we have all the information before it's included in our case list.

So the first part of the explanation is that there is just an understandable lag between onset of case and the time it appears on our chart, and that's just true of almost any infectious disease pattern that we monitor in public health.

But in addition, we are hoping that our alerting process and our travel advisories and the reduction in travel to the affected areas in Asia, as well as the measures that are being taken in those countries to contain spread are beginning to have an impact. An optimistic point of view would be that perhaps we are beginning to see the benefits of those containment measures.

On the other hand, we must remain vigilant. We learned today about situations where travelers have left one country in Asia and traveled to another country and have set off additional cascades of transmission. So there is nothing to suggest that an infected traveler could not come to this country and initiate a cascade of transmission. We have to remain vigilant and do everything we can to continue to detect cases at their earliest presentation.

Let me take another question from a reporter here in the room, please.

QUESTION: Hi. In today's MMWR the CDC reports of 13 probable cases for which you have laboratory findings, and 6 of those have been positive, and 7 have been negative. What does that say about the case definition for probable cases and the tests themselves?

DR. GERBERDING: We have acknowledged all along that the SARS case definition is very nonspecific, and we fully expect that as our testing is more and more comprehensive, and we understand better the accuracy and sensitivity of our tests that we're going to have included people here in the United States and probably in other countries who have something besides coronavirus infection as the cause of their clinical presentation.

Basically the illness that we're talking about is an atypical pneumonia. When the pattern occurs in a traveler to an affected area, it increases the likelihood that it is a SARS case, as we have come to understand it. But the fact that some of our probable SARS cases are not virologically positive is not surprising. We also remain open, and as we've been saying all along, we recognize that this is still a work in progress. We're learning as we go. And we want to be open to the fact that there may be other explanations for the clinical syndrome that we're seeing and we have to keep looking.

So it will be a high priority to continue to investigate the coronavirus negative SARS patients to determine what if anything else is accounting for their illness, and those kinds of evaluations are certainly in progress.

I'll take a question from the phone, please.

OPERATOR: Yes. There's a question from Larry Altman with the New York Times. Please go ahead.

QUESTION: Yes. Rob Webster, this morning, talked about there being a difference in the virulence of the strains that were found in the Amoy Gardens in Hong Kong, and in the strains between Canada and the United States. He didn't specify. He came back from Hong Kong last night, but do you know or can you explain what CDC knows about differences in strains? He didn't say if that was virological or epidemiological, but that's what he said at the press conference.

DR. GERBERDING: Yeah. I can't really speculate about what evidence led to that statement on his part. I did see that statement. What I can say right now is, as we pointed out in the MMWR today, we're dealing right now with 7 virologically confirmed patients here, and it's really much too small of a number to draw any conclusions about virulence.

We have sequenced the virus. The virus we've sequenced here is the virus that came from Asia. It's remarkably similar to the sequence that the Canadians developed, so we'll have to do more sequencing before we can explain whether any of the strains are evolving in any kind of significant way from a molecular basis. And then of course we'd have to know a great deal more about whether there's any clinical relevance in the presentation of one strain or another.

I'd love to know why some patients are sicker than others, and why in some populations there seems to be a higher attack rate of the pneumonia in others, but it's just really preliminary I think to ascribe that to the virus, per se. We have a lot to learn.

Let me take a question from a reporter in the room, please.

QUESTION: Dr. Gerberding, thank you. Can you tell me, are you satisfied with the cooperation you're now getting from China, and what do you make of the recent quarantine of the hospital in Beijing? Is my first question.

And the second question is: can you tell us what came out of Secretary Thompson's meeting with the pharmaceutical industry yesterday?

DR. GERBERDING: We are impressed that there has been a number of steps taken in China to really demonstrate cooperation with WHO and with the CDC collaborators that are part of that overall process. We have one of our most respected scientists in Shanghai right now. And he has full access to hospitals and is really able to evaluate the situation there. And we're learning a great deal as we go forward in that.

I think it's also fair to say that China is a very big country; there are many provinces there, and it's going to take a great deal of time before we really piece together the full picture there. So that should not be interpreted as lack of cooperation at this time; it should be interpreted as the need for complex epidemiology and a lot of retrospective assessment.

We are very concerned about what appears to us to be ongoing transmission in certain areas of China. I think the WHO shares that concern, and that's the basis for the ongoing travel advisory to those areas.

Whether or not the steps being taken to contain the problem there are having an impact is something that we just can't address at this point in time; there just isn't enough information.

Now, Secretary Thompson has made it very clear from the very beginning of this that we want to aggressively and assertively engage the private sector in antiviral therapy as well as vaccine development. I can't comment specifically on the meeting that he held yesterday, but I'm sure the Department of Public Affairs people will be happy to give you an update and a perspective on that.

My message is just we're extremely pleased with the coordination and also the spirit and the interest that the private sector has shown. We have had many requests for information about the virus, many requests for the virus RNA. And all of these companies are either working on diagnostic tests, antiviral treatments, or vaccines. So it's very encouraging at this point.

Unfortunately, so far the compound testing has not provided any suggestion of an effective treatment. But we remain hopeful that eventually something will show up with activity.

Let me take a telephone question, please.

MODERATOR: We have a question from John McKenzie with ABC network news. Please go ahead.

QUESTION: Yes, Dr. Gerberding. Could you be a bit more specific as to what the CDC Team in Toronto is doing on a day-by-day basis? How many more days will they be there? And have the come to any preliminary conclusions?

DR. GERBERDING: The CDC Team in Toronto is there at the invitation of Health Canada to help assess with really a fresh set of eyes. The problems that have occurred were spread in the health care setting. After very good infection control precautions were implemented, there were still a few cases of transmission of SARS to health care personnel in the facility.

And so when you are doing everything right, you have to back up a little bit and say, "Is there absolutely anything that we're overlooking?" And sometimes getting a fresh set of consultants in can really see things that the people, front and center, miss.

So the role of the team there is to really provide their technical expertise. One of the individuals is a very experienced health care epidemiologist, who's had experience domestically and internationally. One of the individuals is an expert in occupational safety and health and is really extremely knowledgeable about airway protection, masks, and so forth.

And one of the individuals is an environmental engineer, who has a very long experience dealing with air system handling and health care facilities, water, safety, and so on and so forth.

So these folks are just conducting an assessment in conjunction with the health care epidemiologists in the facilities, and learning about what the risk factors for transmission might have been.

At this point I can't predict how long they will be useful, or how long Health Canada will find their presence informative or helpful. We're probably learning more there than we are contributing at this point in time. And I really do look upon this exchange of experts, both that team, but also the fact that CDC has scientists working with Health Canada in their operations center. We have a health Canadian scientist here in our operations center. It just helps so much, and is just the best possible way for us to anticipate what we'll need to be doing here if we are not successful in containing the problem domestically.

Let me take another question from the phone, please.

MODERATOR: You have a question from Elizabeth Kellidan with CBS? Please go ahead.

QUESTION: Hi, Dr. Gerberding. Excuse, me I have two questions. The first is about the death rate. First of all, what is the death rate today, the average global death rate? And what significance are you giving that number? Does that mean that we're finding that this virus is more deadly than we thought? Or is this all about statistics, and being able to diagnose better?

And my second question is about mutation. Is there any evidence right now that suggests that the coronavirus is mutating and producing a variety of strains?

DR. GERBERDING: The death rate calculated by WHO, based on the probable case definition, is almost 6 percent. It's gone from 3 percent to 3.5 to 4, and it's now running between 5.9 and 6 percent. I don't infer anything about the death rate, except that I wish it was zero. I think the fact that's changing is not at all surprising, given the fact that the case definition is changing, and that we are learning as patients get further evaluated that some of the people who were on the list turn out not to have SARS, and are taken out. The more people who go off the list, the higher the proportion of mortality will really be. So there is not comprehensive predictability about how the number will play out in any given community, because different countries are using different definitions to include patients in the list.

I don't think we have any evidence right now to say one or another whether the virus is evolving or mutating. It is an RNA virus. It is a single stranded RNA virus. These viruses in general have a propensity to evolve or to make mistakes when they copy themselves, and also to potentially exchange genetic material. So, we will certainly be alert to that, but that is not something that we can document at this point in time.

Let me take a question here.

QUESTION: Doctor, as you likely know by now, Toronto and Canadian officials are very upset over the WHO's designation and travel advisory that they have. Yet the CDC still has not issued as stringent a warning. Do you think the WHO overstepped its bounds, or are you all using different criteria?

DR. GERBERDING: I think right now the over-arching perspective on this is how incredible the collaboration has really been. We don't always agree on everything, but the exchange of information and the collaboration has really been remarkable, and I think that's likely to continue.

We in the United States and Center for Disease Control and Prevention have a responsibility to do the kinds of public health interventions that we think are appropriate and measured for our citizens. And our understanding of the information we have available right now is that U.S. citizens traveling to Canada are not at risk for SARS if they stay out of hospitals and follow some common sense precautions. If we learn differently or if problems emerge that suggest that cases of SARS are cropping up in Toronto, that cannot be explained by the existing patterns of transmission, we would of course adjust our advice in the same way that we have for other countries where we see ongoing community transmission that can't be linked back.

So it's a matter of looking at the scenario. First of all, where is the risk? Where in the community can you predict where the risk currently is. Are travelers likely to be in a situation where they can't assess their risk or can't predict if they're exposed or not, and right now that does not characterize our understanding of the situation in Toronto.

We're also communicating with the officials from HealthCanada and the WHO, and we're going to get all of the information out on the table, and we look forward to hopefully in the future developing a consistent set of criteria for different levels of travel advisories and alerts. I think that would help everyone if we could come to some kind of a more global agreement about what the criterion are, and then everybody would understand what we're doing and why we were doing it.

So we are looking at ways to do that now. We've had discussions with officials in the Canadian Health Department this morning, and I look forward to bringing that up to the WHO as well in our next conversation.

Could we have a question from the phone, please.

OPERATOR: We have a question from Elizabeth Cohen with CNN. Please go ahead.

QUESTION: Hi, Dr. Gerberding. I was wondering in the MMWR, where it mentions the health care workers who initially were not protected and who were offered the furloughs, I was wondering why weren't they protected, and does this say something about health care workers and whether or not they are protecting themselves when someone comes in who may, in fact, have SARS?

DR. GERBERDING: Well, you know, we are doing the kinds of things that we can think of to help people become self-aware that they may have been exposed to SARS. So an individual who's traveled to an area, this individual was in a situation where there was a likely of known exposure to people who have had contact with SARS patients, that if they get ill, they can have the information necessary to tell the health care providers that they could be at risk for SARS.

I don't specifically whether this particular patient had that awareness or had been given the information to make him aware of it or not, but that's an important part of this overall effort and one that is amazingly successful. Many, almost all of the U.S. suspected and probable SARS cases identified themselves as being potentially at risk because of their travel history, and this really helps us a lot and also helps the health care workers at that point of contact in the delivery system to use the protection they need.

Part of the reason why we put out the alert and are alerting passengers returning from Toronto about the possibility of SARS so that they will recognize, if they become ill within the next 10 days, so that they need to let their providers know so that appropriate precautions can be taken.

So I don't know what the information exchange was specifically in that exact case, but we're working hard to make sure that that doesn't happen again.

I'll take a question from a reporter in the room, please.

QUESTION: Apparently, there are three new cases in the Baltimore area, and one is involving a physician who traveled to apparently Detroit and also Toronto. Can you tell us what you know about these.

DR. GERBERDING: We don't comment on specific reports that haven't been validated or reported to us in detail by state health departments. So, as usual, with public health and CDC, you have to go to the state health department to get that information until it's been confirmed and included in our reporting here.

I'll take a question from the phone, please.

OPERATOR: We have a question from Maggie Fox with Reuters. Please go ahead.

QUESTION: Hi. Everybody pretty much asked my questions, but I was hoping you might be able to comment further on what sort of issues might be at work in Canada where they are doing all of the right things, as you say, and yet still there's some hospital transmission. What are some things that might be going wrong there?

DR. GERBERDING: I can only speculate. I have no data and no personal perspective on this, other than my past life as a hospital epidemiologist worrying about similar problems with other infectious diseases.

One of the major issues is that in this illness you need to probably be 100-percent adherent to the recommendations about airway precautions or airborne precautions, and that's because we know that there are certain patients that appear to be very highly infectious.

And so if a mask is recommended, for example, an N95 respirator mask for health care personnel, not only do they need to wear that mask for all contacts with the patient, but they need to make sure that it's properly fitted. If there's any leakage around the mask, it really negates the whole value of having that filtration factor in front of your breathing zone.

So that's one of the important things to look at; is there any improvement that could be made in the respiratory fit testing of the masks that are being used by health care personnel.

Another potential problem that had cropped up in U.S. hospitals during the tuberculosis era, when we were especially concerned about TB transmission in hospitals because of the multi-drug resistance profile, even though you put patients in a room that has the appropriate ventilation system, sometimes the room is not actually functioning at that level of ventilation.

And there are measures that have to be taken to identify are the air exchanges adequate, is the filtration of the room actually happening the way you think it is and is the room really in negative pressure so that it's not actually blowing organisms out into the health care environment and instead filtering them back into the filtration system.

And it's quite easy for rooms to get "out of balance," and so that, I'm sure, is one of the things that our environmental engineer is looking at in the facilities there to make sure that the engineering of the airborne precautions is completely adequate. It's very easy for rooms to go out of balance. So there are a number of possibilities, and I'm sure we'll learn more as the experts there and our team put their heads together and come up with that kind of information and analysis.

It will be a lesson for us, I'm sure, as we see what the situations were there, and we will certainly make that information available so that we can learn from it and apply it broadly.

May I take another question from here in the room?

QUESTION: Hi, I was wondering what are the factors that have contributed to the low transmission rate here in the U.S. of SARS, anything that you can point to?

DR. GERBERDING: The low transmission rate in the U.S., one possibility is good luck, that we haven't had the right combination of someone who's highly infectious and inadequately protected health care personnel. So that's certainly one factor.

I think we may also learn, as we complete the serologic and other testing of the case patients in the U.S., that many of these individuals may not have SARS at all, and that would certainly account for the lack of SARS transmission and I would like to credit the vigilance of the public health officials in our country and the health care providers at the front line, who I believe, from everything I've been able to ascertain as the reports come in, have really done a great job of early detection.

So as I mentioned before, the travelers themselves are aware and do the right thing, follow the instruction of the health alerts and seek care, but the health care system is able to use to appropriate infection control precautions to prevent spread, and people have just been amazingly cooperative. I think it's really been a wonderful experience to see how the different components of the system really can interact constructively, and that may very well be playing an important role here.

A question from the telephone, please.

OPERATOR: There's a question from J. Rosenberg with Newsweek. Please go ahead.

QUESTION: Hi, Dr. Gerberding. I'm wondering if you can tell us what the latest is that we know in terms of transmission of the virus. There have been some reports about SARS being able to survive as long as 24 hours on inanimate objects. What can you tell us about that, and also other ways that you're suspecting it could be transmitted?

DR. GERBERDING: We continue to have an open mind about all possible modes of transmission. The epidemiologic evidence still suggests that face-to-face contact or droplet transmission is accounting for by far the largest proportion of cases. Airborne transmission is certainly a concern in certain of the outbreaks that have been evaluated. The fact that you can find at least PCR evidence of virus RNA in stool, that at least raises the question about contaminated environmental objects and fecal/oral spread as playing a role in some settings, as has been suggested in one of the apartment complexes in Hong Kong.

The bottom line is that we have pages of epidemiologic investigations that are ongoing right now with partners around the world to try to get to the bottom of these questions, and the only way we're really going to know the answer to them for sure is when we've accumulated enough experience and enough data in our cohort studies and case control studies to really tease out all of these factors. It's going to be very difficult to say for sure that something is not a mode of transmission, but over time we may be able to provide at least some quantitative estimates about what is the probability of some of these, up to now, less likely modes.

Question over here.

QUESTION: Dr. Gerberding, realizing that we're still talking in essence about weeks and not years, but you've had the benefit of some time now and this unprecedented cooperation around the world as you describe it and the pages of information. Are we beginning to see trends that you can identify in who is getting this more severe strain of SARS versus what seems to be a less severe strain here in the United States?

DR. GERBERDING: We really are not characterizing this as a severe strain or a less severe strain. We just cannot ascribe the epidemiologic patterns to that particular observation. There are so many factors that influence disease severity. One of them is strain characteristics of the virus. Another is the host, how healthy is the person who comes in contact? Do they have risk factors that increase the hazard of having infection with a virus like this? Their immunologic defenses, do they smoke or not smoke? I mean these are all questions that we'll want to be asking and getting answers to to determine whether there are other predictors of severity.

And another possibility is that the dose of exposure is important. If you get a high dose perhaps you get sicker faster, get more ill, or less sick. So it's just speculative right now. Those are exactly the questions we're trying to answer.

Question over here.

QUESTION: Could you elaborate on the--what you were talking about, what's going to happen at the end of the week? Does that mean if I'm driving into Canada by the end of this week or weekend, I'll be handed a card? And if you could just clarify what you were talking about, the more information, the more travel alerts. And also has Major League Baseball asked the CDC for any kind of advice or guidance? There have been reports that they might be advising teams that travel to Toronto to do various things, and only one of the things are what CDC has recommended, and that's stay away from health care facilities. The other ones seem a little different. I'm just wondering if Major League Baseball has asked for advice from you guys.

DR. GERBERDING: I'm going to ask Dr. Cetron to take the first question.

With respect to the concern on the part of athletes and baseball players in particular, we have had a couple of inquiries from various members of the sports community, asking about what advice is appropriate for teams traveling to Toronto for games. And we are really providing exactly the same information to those members of the traveling community as we are to anyone else, that right now the evidence does not suggest any hazard to them from playing a game or participating in a social environment. They should not go to health care facilities that are taking care of SARS patients if they can avoid it, so if they're visiting someone who is hospitalized or sick, it would be best not to plan to do that at this point in time.

And there are some other common sense things again that should apply to everybody like hand hygiene and cover your nose if you cough and sneeze. But we have no specific recommendations for that group of travelers.

We are aware that there's a great deal of interest in it, so we're going to sit down and see if we can identify specifically what the concerns and needs are and then perhaps tailor some specific advice and guidance that would be useful to reassure them.

Let me take the question--oh sorry, yes, go. Dr. Cetron is the scientist who's responsible for the activities related to health alerting, travel advisories, in our Division of Quarantine and Global Migration.

DR. CETRON: Thank you very much for the question. It amounted to the specifics of when do you get the yellow cards and what's the process. The process is that by the end of this week, hopefully tomorrow at Toronto Pearson Airport and certainly by Saturday at some of the land crossings, travelers leaving Toronto at Pearson Airport, as they pass through the U.S. Customs and Immigration process, will receive the yellow health alert card, and it has additional languages, as we mentioned previously to include French. That amounts to somewhere between 3- and 400,000 outbound travelers a month to somewhere, as Dr. Gerberding said, about 50 different airport locations in the U.S.

So they'll be getting them at the point of departure, rather than the point of arrival, and that's just a logistic operation. We are grateful to our partners in the Department of Homeland Security for being able to participate in that process.

With respect to the land crossings, we will be implementing that as well through the Bureau of Customs and Border Protection, and they will get them as they cross in the major crossing areas. Now, the land crossings are very voluminous. In the two large crossings, that's 25,000 crossings a day. We are aware that not everybody crossing there from Canada into the U.S., this is mostly the Ontario traffic into the United States, and we are well-aware that not all of those people will be coming from Toronto.

However, logistically, with that volume, to actually sort out who really needs one and who doesn't will be challenging. So people will get that. I suspect that up to 90 percent, we're told, of the people crossing there are commuters who regularly go back and forth to work on one side or the other, and quickly they will say, you know, "I'm not one of these folks and, yes, I've gotten one yesterday or this afternoon and won't need one." But that will be a very large volume.

As Dr. Gerberding pointed out, overall we're talking about 60 million arrivals from the Toronto area a year. So it's quite a logistic challenge, and we're grateful to everyone who's assisting with that process.

DR. GERBERDING: We'll take a question from the telephone, please.

OPERATOR: We have a question from Cathleen Downey with HealthScout News. Please go ahead.

QUESTION: Thank you. Can you discuss the wide variations in death rates among countries? Previously, in a briefing, you alluded to perhaps hospital infection control practices, and this morning you talked a little bit about the different case definitions, but any other reason why there's this wide variation in death rates?

DR. GERBERDING: I don't have an explanation for the difference in death rates, except that as an epidemiologist or a statistician I would say that, overall, thankfully, the numbers are still very small, and so this kind of variability is consistent with the fact that this is still an evolving problem. There may be differences in the care that patients receive, there may be differences in how quickly they get into the health care system.

There are lots of reasons why death rates vary from one area to another, including the characteristics of the population that's affected. This is typical for infectious diseases and not surprising or something unique about SARS.

Let me take another telephone question, please.

OPERATOR: We have a question from Betsy McKay with the Wall Street Journal.

QUESTION: Hi, Dr. Gerberding. Thank you very much.

I was wondering if I could ask a question again about diagnostic testing. The other day you said that or you referred to the fact that with the genome sequence on the internet now, that gives a possibility for many organizations, groups, companies to develop PCR-based tests.

I'm just wondering if you can comment on how many of these such tests you know of are being developed and the accuracy of these tests, particularly the Rapid Tests.

DR. GERBERDING: We don't know how many entrepreneurs are developing PCR-based tests right now. We have had about a dozen companies contact us for additional assistance, re-agents or information or virus sequences. So that may be the tip of the iceberg. I can't really speculate, since we have no way of really knowing what's going on, particularly from the global perspective.

However, the PCR-based tests are typically tests that can have some complications in interpretation. They are sometimes falsely positive because they're so very, very sensitive, and they can become positive if the laboratory in which they're being run is not absolutely pristine about any kind of cross-contamination or carryover. So that's one issue.

The other practical issue is the one that we're working so hard on right now, and that is, before anybody, whether a private company or a federal agency, uses a test, it has to be validated against a wide variety of patient specimens to determine whether or not it's sensitive, specific and accurate. In order for a company to really validate its test, it will need to have access to a panel of specimens and determine whether or not the test can be reliable in detecting positive and negative results accurately.

So it's likely to take some time for anybody to really have a test that we would have confidence in, and that validation process is something that has to go hand-in-hand with a lot of effort at FDA.

Let me take a question from the floor, last question right here.

QUESTION: Dr. Gerberding, first, let me say thank you that in your last briefing you tell the audience of a new [?] TV that vinegar is not effective with this infection. I think the news is passing into China right now.

I have one question. We know that 24 of the 31 provinces in China has recorded about SARS cases. Do you think WHO should actually be proactive sending working groups to different provinces, instead of rather just focusing Shanghai situation?

And the second question is invading the universities because, basically all of the universities and schools have been closed down, and we're wondering how people handle the situation. Many people try to rush out of Beijing. Is there any better way to handle this crisis?

DR. GERBERDING: It's really hard for me to offer advice about what would be a good idea in Beijing or China, since I'm not there, and I don't have really the experience to understand the true scope of the problem there. We know that WHO is very interested in doing everything that it can, and we, in the United States, are certainly sending our staff to assist in places where the requests are being made.

The WHO is actually not a large organization. I think Dr. Hayman mentioned something like 30 or 40 people at WHO total to be involved in the SARS operation. So they are very involved in working with scientists from a whole variety of the international community to assist in this way. I'm sure they will be doing everything they can to contribute if requests are received from various areas of China.

Our CDC team, as I said, is there and has been very pleased with the collaboration and cooperation at this point in time, and we are already planning that additional staff will be going to China very soon. So we'll do what we can to help. Thank you.

Thank you for your interest in this issue, and we will continue our commitment to update you as we learn new information and get through the next phase of this problem.

Thank you very much.

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