The latest numbers on the Ebola outbreak are grim: 2,473 people infected and 1,350 deaths.
That's the World Health Organization's official tally of confirmed, probable and suspect cases across Guinea, Liberia, Sierra Leone and Nigeria. But the WHO has previously warned that its official figures may "vastly underestimate the magnitude of the outbreak."
So how bad is it really?
That's the question NPR put to several people who have been carefully watching the outbreak.
There's no scientific way of knowing exactly how wrong the official numbers are, says Joseph Fair, an infectious disease doctor who has been acting as a special adviser to the health minister of Sierra Leone. "At a bare minimum, I would guess they're probably off by 20 percent," he says.
Once public health workers identify someone with this disease, Fair says, they have to find everyone else who might have gotten exposed through contact with that person. And that hasn't been easy.
Even if someone tests positive for Ebola, he says, public health workers may return and find that the person has simply disappeared.
"They're traveling, usually by public transport, and coming into contact with a lot more people," Fair says.
The health agencies of these poverty-stricken countries don't have the staff they need to track down all these people who may have been exposed. Unlike previous Ebola outbreaks that hit isolated, rural areas, this one is affecting many more people in a more urban environment.
Adding to the difficulty is a climate of distrust created by years of war and conflict.
"Because people are so afraid, in some instances, if a relative dies in a home, all the others run away instead of going toward the clinic to report themselves," says Roseda Marshall, a Liberian pediatrician who is president of the Liberia College of Physicians and Surgeons. She's currently in the U.S., trying to raise funds and support to help fight Ebola.
"Obviously, the statistics we're getting is just scratching the surface," Marshall says. "When we say we have so many suspected cases, so many probable cases, so many confirmed cases, that's just the ones who are coming in for testing."
Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, agrees that people running away from hospitals and quarantines are a real problem, making him fear that this outbreak will get worse before it gets better.
"A considerable number of people are going to die before we get it under control," Fauci says. "Obviously, as a physician and as a health person, that bothers me."
But he says some government workers who have been to West Africa actually think the official numbers aren't that far off.
"They think it's likely a bit underreported, but not substantially," Fauci says. The number of people affected is not likely to be "many, many, many-fold greater" than what the WHO has estimated, he added.
One simple reason the numbers are wrong is that there's currently a backlog in getting cases entered into the official counting system, says Barbara Knust, an epidemiologist with the Centers for Disease Control and Prevention who has been working on the outbreak.
"We probably will have much more accurate numbers in the coming weeks," she says.
Having good numbers, she says, is key to understanding where Ebola is really spreading and where public health workers need to focus their efforts.
KELLY MCEVERS, HOST:
Now for some rare good news on the Ebola front. One of the two Americans who contracted the deadly virus in West Africa is being discharged from an Atlanta hospital today. The second one might be discharged soon. They are among roughly 2,400 people who the World Health Organization says have contracted Ebola. More than 1,300 people have died. It is the World Health Organization, or the WHO, that is tasked with tallying these numbers. But, the agency also says the figures might, in their words, vastly underestimate the magnitude of the outbreak.
NPR's Nell Greenfieldboyce wondered what the real numbers might be.
NELL GREENFIELDBOYCE, BYLINE: Joseph Fair is an infectious disease expert who has been working on Ebola as a special advisor to the health minister of Sierra Leone. He says no one believes the official numbers on the outbreak.
JOSEPH FAIR: I can tell you why we all - all, I think, would say we think it's vastly underestimated.
GREENFIELDBOYCE: He says you just can't keep track of everyone who may have the disease. Once public health workers identify someone with Ebola, the goal is to find everyone else who might've gotten exposed through contact with that person.
FAIR: You know, it's simply asking them - who did you have contact with? Or, when you go to the village where they are located you're asking everyone in their family - who did you see them with? Did you personally have contact with them?
GREENFIELDBOYCE: If someone's been exposed, workers can take some blood for testing. When the results show that someone has Ebola they go back with the news and often, that person is gone.
FAIR: They're traveling usually by public transport and coming into contact with a lot more people. So imagine that person that I have just identified is now a positive and then I come back and they're not there, but I find out that they've taken a bus to Freetown and that they vomited while they're in the bus - so now everyone in that van is now a contact. And not only they are contacts, but everyone they've had contact with after that are contacts.
GREENFIELDBOYCE: Fair says there's not enough workers to then track down all these people to see who's infected. So the official figures have to be an undercount. He just doesn't have a scientific way to measure the error.
FAIR: At a bare minimum, I would guess they're probably off by 20 percent.
GREENFIELDBOYCE: One Liberian physician says she suspects the official numbers are just scratching the surface.
ROSEDA MARSHALL: People are dying every day that nobody knows.
GREENFIELDBOYCE: Roseda Marshall is president of the Liberia College of Physicians and Surgeons. She says the countries being hardest hit are poor and have been torn apart by conflict. People are terrified. They don't understand the disease. They don't trust the authorities.
MARSHALL: And because people are so afraid, in some instances, if a relative dies within a home all the others run away instead of going to the clinic to report themselves.
GREENFIELDBOYCE: That makes some experts worry that this will get worse before it gets better. Anthony Fauci is head of the National Institute of Allergy and Infectious Diseases.
ANTHONY FAUCI: You know, a considerable number of people are going to die before we get it under control and that, obviously as a physician and as a health person, that bothers me.
GREENFIELDBOYCE: But he says some government workers who've been to the region don't think the official numbers are that far off.
FAUCI: They don't think it's like many, many, many-fold greater people that are being reported. They think it's likely a bit underreported, but not substantially.
GREENFIELDBOYCE: Whatever numbers we're hearing, they're lagging behind what workers there are actually gathering. Barbara Knust is an epidemiologist with the Centers for Disease Control and Prevention. She says Ebola cases have to be entered into the reporting system and there's currently a backlog.
BARBARA KNUST: We probably will have much more accurate numbers in the coming weeks.
GREENFIELDBOYCE: She says having good numbers is key to understanding where Ebola is really spreading and where public health workers need to focus their efforts.
Nell Greenfieldboyce, NPR News. Transcript provided by NPR, Copyright NPR.