New Ebola Strain: Many Unknowns

Few things in life are scarier than Ebola. The virus has killed 9 of 10 victims in some outbreaks, and the effects are particularly gruesome—the bug causes massive bleeding. Ever since the first outbreaks in 1976, which erupted simultaneously in Zaire (now the Democratic Republic of the Congo) and Sudan, scientists had identified a total of four strains. Now there's a fifth. The outbreak earlier this month in Uganda has claimed 22 lives, including a doctor in Kampala, raising fears of an urban outbreak and causing rumors that the virus is a milder type that could spread more easily beyond Uganda and the African continent. Tom Ksiazek, chief of the pathogen branch of the Centers for Disease Control in Atlanta spoke with NEWSWEEK's Fred Guterl about how dangerous the outbreak may be and what scientists are doing to investigate. Excerpts:

NEWSWEEK: How is this virus different from the four other known strains of Ebola?
Tom Ksiazek:
This virus is not like any of the four other ones. It's about as different from the other four as they are from each other.

How do you know?
That's based on preliminary information about the [genetic] sequence of the virus itself. These are RNA viruses, so we're looking at the [nucleotide] base composition of small pieces of the virus. We've managed to isolate the virus and are growing it in cell cultures. We're still working on getting more sequencing.

What have you learned about this particular strain?
There's been a lot of speculation in press reports about it being less pathogenic, or perhaps not causing as much bleeding [as other strains]. I've seen other people speculating that this will make it more difficult to control. Our perspective is, you need data to say those things. Specifically when you're dealing with a new virus. You have to develop your data as you go along. You want to probably limit your data to those who you can demonstrate are really patients who have been infected with the virus. It's very early in the process now. We've diagnosed a few patients in our lab, and those are the only patients we really know are Ebola patients.

You mean many people reported as victims of this Ebola outbreak may be sick with some other disease?
You're seeing reports from Uganda that there's—you name a number—79 patients and 22 deaths. How many of those patients are really known to [have the] Ebola virus? There's a case definition that's developed that says, "This guy's got a headache and four or five other symptoms." There are a lot of other things that will give you symptoms like that.

Like what?
If you've ever had a serious case of flu, you'd be included in that group. Or early malaria, for that matter.

So you're saying that we still don't have a true picture of the mortality of this particular strain?
It could be higher, it could be lower [than what's been reported]. It really has to be based on patients that you're doing some rigorous diagnosis on. If you cast a wide net, you end up with a lot of fish in the net that you're not really after.

What are you doing to get better data?
We've sent a team to establish a lab in Entebbe, south of Kampala. We'd like to get samples from suspected patients and have them tested, and they'd either be called confirmed cases or put in some other category. And here [in Atlanta] we're working to get assays that are targeted for the new virus, [which would enable us to] test for presence of the virus.

What will more complete sequencing of the virus tell you?
It may tell us something about its evolutionary relationship with the other viruses, but not how pathogenic it will be. That has to come from the field. At this point we're waiting to get more sequence [of genetic data] so we can have a better perspective on it.

When will that happen?
Within a week we'll have more [sequencing] information and make some sort of announcement to the government of Uganda. To find out how pathogenic it's going to be, that has to come from the field. We need to know how many patients die and how many of them live. That really defines the mortality.

Is this a milder strain than those you've seen in the past?
That has to be based on data. As far as we're concerned, there's not a lot [of data] suggesting that this is all that different from other strains. It's premature to say that it's milder or not milder.

Would a milder strain be worrying because it would be more likely to spread?
I would say that if it's milder, it's less likely to be shed in huge quantities, so people who've come in contact with patients are probably less likely to transmit the disease than [if it were] a severe strain.

How does this virus spread?
Through very close contact with patients. A lot of misinformation that's being spread is that it's transmitted through the air, but generally you have to have pretty close contact with somebody who's pretty seriously ill.

What about the doctor who traveled from the outbreak area to Kampala and died there? Are you concerned that he might have taken the outbreak to Kampala?
If he was relatively well when he traveled to Kampala, it's unlikely that the people he had casual contact with resulted in any infection. We'll check to see if he's had any unusual exposure to individuals after that. There's always concern. There tends to be a lot of reaction and misinformation that can border on panic. What we attempt to do is refamiliarize people with past outbreaks rather than speculating on what might happen.

So you're not worried too much about a wider transmission of the virus than in the past?
There's always some concern. Let's be clear: this is a disease you don't want to get. But the outbreaks generally occur in underresourced areas where it's necessary to get folks in and help them with things like infection control practices and protective gear, so the outbreak stops. There's a lot of concern—you don't want this going places. But in a developed country transmission probably wouldn't get started.

Should travelers avoid Uganda?
There's been some stuff in newspapers that might tend to make people overly concerned. We don't advise people not to travel to Uganda. If you were a medical missionary and were treating patients in these areas, that would be cause for concern. But if you're traveling to see animals, you don't need to worry too much.