But there have been other repercussions as well, as the outbreak slows economic growth on the continent. One export that's produced near affected countries? Cocoa.

　　Our economics correspondent, Paul Solman, sought to understand how those market forces are working, part of his ongoing reporting on Making Sense of financial news.

　　PAUL SOLMAN: Prepping for Halloween, 2014, in New York City, where the spiders may be less scary than what they're liable to snare, the urban cockroach.

　　But, quite seriously, there's an economic menace this season, Ebola in West Africa, which grows most of the world's cocoa, the main ingredient of chocolate.

　　In Times Square, crossroads of the world, in this case, M&Ms' world and Hershey chocolate world, some confectionery consumers were preparing for a possible shortage. Will this mother stash chocolate for trick or treats because of Ebola?

　　WOMAN: Of course I will.

　　PAUL SOLMAN: You will?

　　WOMAN: Sure.

　　PAUL SOLMAN: And all over town, chocolate buyers have been paying an Ebola premium.

　　Has the price of this gone up?

　　MAN: Yes. Two months ago.

　　PAUL SOLMAN: Two months ago.

　　So a Kit Kat bar is now a buck thirty five, up a dime, on the sidewalks of New York, and the noisy platforms below.

　　Has the price of chocolate gone up?

　　MAN: Ten cents.

　　PAUL SOLMAN: Up 10 cents here too.

　　Meanwhile, at Dante Confections, maker of perhaps the finest truffles in Massachusetts, and surely the finest in North Billerica, president Santi Falcone's one-year cocoa contract with agribusiness giant Cargill came due in September.

　　SANTI FALCONE, Dante Confections: I almost fell out of the chair when I saw it. I thought it was a big mistake there — 26 percent? In 25 years, I have seen increases, 3 percent, 1 percent, stay the same, but, God, not 26 percent. You know, I mean, that's a little crazy.

　　PAUL SOLMAN: And how much of that price increase did you pass along to your customers?

　　SANTI FALCONE: I basically compromised by increasing the price between 9 to 10 percent. And when the candy shop gets a 10 percent price increase, he will have to raise it 20 percent.

　　PAUL SOLMAN: So now to the age-old question when markets move so dramatically: Is the price shock-au-chocolat due to fundamentals, a real change in the cocoa market caused in this case by supply disruption, or market psychology, unfounded hysteria?

　　Back in Manhattan, David Martin runs his own hedge fund, has been a commodities trader since the 1980s. This year, he explains, the price of cocoa had been rising and subsiding with the conflicting reports about the seriousness of the Ebola outbreak. It began last spring, when the cocoa market:

　　DAVID MARTIN, Martin Fund Management: Rallies up on rumors of Ebola, comes off because they realize that it may not be a problem, and then reported cases come out of Africa, and the market has a huge spike up. People start to panic.

　　PAUL SOLMAN: People buying cocoa, that is, for a growing global market, China in particular. And why wouldn't they panic? Consider this CDC map of West Africa with, on the right, the Ivory Coast, the world's foremost cocoa grower.

　　DAVID MARTIN: You have the ivory coast here. You have the bordering countries. In dark orange are areas with confirmed and probable cases of the Ebola virus infection. A lot of the people who live in these areas come to work in the Ivory Coast to help with the harvest. If they fall ill or die, they can't come to work.

　　If they do come to work and they're infected, they infect these people. There's no one left to pick the beans, deliver them to the port, and make this whole system flow. So the fear is that if you disrupt this commercial activity, this whole supply chain, that's going to cause the price to skyrocket.

　　PAUL SOLMAN: So, a rational market response to Ebola, says Nobel laureate economist Paul Krugman.

　　PAUL KRUGMAN, The New York Times: Of course it's disrupting the economies of West Africa. Why would you be surprised if the prices of goods coming from West Africa go up? And if it's true, that, yes, we don't yet have a shortage, well, markets are supposed to anticipate that.

　　PAUL SOLMAN: But wait. The Ivory Coast remains Ebola-free and is actually ramping up its exports to take advantage of the price rise. And high-end cocoa comes from other places as well. In Africa, maybe, but so what?

　　JOE SALVATORE, Chocolate Entrepreneur: Africa is such a big continent.

　　Brooklyn chocolate entrepreneur Joe Salvatore.

　　JOE SALVATORE: What's happening in West Africa is not happening in East Africa, what's happening in Madagascar.

　　PAUL SOLMAN: Madagascar, an East African island almost exactly as close to Liberia as Miami to the North Pole, is where Salvatore volunteered for the Peace Corps, and then helped start a business to boost the local economy.

　　Madecasse now makes chocolate from start to finish in Madagascar, distributes to the U.S. from Williamsburg. Its face-to-face way of doing business buffers it from the commodities market and all the middlemen between grower and retailer.

　　JOE SALVATORE: What we're doing is, we work directly with farmers. When you take a lot of the middlemen out of that equation, you're able to actually save money on both sides.

　　PAUL SOLMAN: And it's middlemen who hiked the price to those kiosks in New York and the likes of Santi Falcone.

　　Do you think that they were simply passing along to you the price increase that they felt when they're buying the raw cocoa, or that they were taking advantage of a rise in prices to stick it to people like you?

　　SANTI FALCONE: Maybe they are sticking it to the little people. Maybe, maybe not. But, certainly, I don't like it, and my customers don't like it.

　　PAUL SOLMAN: But, again, is the price rise based on reality or imagination? To veteran cocoa trader David Martin, in the short run, it's irrational market psychology, not fundamentals, that drives investors.

　　DAVID MARTIN: Some sort of hysteria that, I don't want to buy this bag of raw cocoa beans because it was handled by people that may have the Ebola virus. They see the images on the news of people suffering and dying, and everyone just afraid to even go near them. That's a pretty emotional story, I think.

　　PAUL SOLMAN: And, surely, emotions play a hallowed role in market swings, like those lately in oil or stocks.

　　In the end, says Martin:

　　DAVID MARTIN: Price movements aren't about the values of the companies of the stock market. They're not about the price of cocoa or the price of coffee. They're about the study of human behavior and how humans react.

　　PAUL SOLMAN: So how might Ebola cause humans to react in the cocoa market, now that the winter holidays are coming? How about Valentine's Day and Easter? The price has dropped almost 10 percent, but, says Falcone:

　　SANTI FALCONE: The salesperson for Cargill, he feels that the market is still going to go further up, that the Asian market is taking all of the cocoa, which is driving the market up.

　　PAUL SOLMAN: But your suspicion is that this was a scare, the Ebola scare, and then speculators jumping in and driving up the price?

　　SANTI FALCONE: I would assume that. Wouldn't you agree with me, or…

　　PAUL SOLMAN: Given what we have heard, yes, I guess we would. But, as with all swings, in all markets, how would you ever know?

　　I'm Paul Solman for the "NewsHour" in New York.