When the first cases were reported in Syria 275 years ago, it was called "the Aleppo boil" or "the Aleppo evil." And for good reason: The parasitic illness spread by sand flies causes nasty skin lesions that leave victims scarred for life physically and can leave emotional scars as well.

The disease, now known as Old World cutaneous leishmaniasis, or CL, is not unique to Syria. It's found in parts of the Middle East, Africa, Asia and southern Europe, according to the Centers for Disease Control. But ever since Syria's civil war started in 2011, what had been a persistent — but relatively controlled — nuisance has turned into a full-fledged outbreak.

A decimated health care system, millions of displaced people and unsanitary conditions created "a perfect cocktail for infectious diseases to spread," says Alvaro Acosta-Serrano, a senior lecturer at the Liverpool School of Tropical Medicine.

He and his colleagues have been sounding the alarm about CL in Syria. The country had an estimated 23,000 cases a year between 2004 and 2008. Things changed dramatically after the conflict began. By 2012, 53,000 cases were reported by the Ministry of Health. In just the first few months of 2013, 41,000 cases were reported.

As for what's happened since then, no one really knows. Gathering reliable data is not feasible in this situation, Acosta-Serrano says, although he suspects the current number of cases in Syria and the surrounding region could be in the hundreds of thousands. Many of the 12.5 million Syrians who've been displaced from their homes now live in overcrowded camps without basic sanitation or waste disposal services — a hospitable environment for sand flies to breed and spread CL in areas where it has not previously been a problem.

But to identify CL requires trained dermatologists and diagnostic testing, both of which are hard to come by right now. According to Koert Ritmeijer of Doctors Without Borders, the scant medical resources available in Syria are reserved primarily for life-saving care. Although CL is regarded as a serious issue, it's generally not fatal. So it has to take a back seat to other health threats.

That's nothing new for CL, which is classified by the World Health Organization as one of its "neglected tropical diseases." Inclusion on the list means that a disease typically affects people living in poverty and hasn't received much attention or funding. As Acosta-Serrano explains, CL fits that definition: "There's no vaccine to prevent the disease. And we're still using drugs discovered 50 years ago. They work, but many of them are quite toxic."

These chemotherapy drugs can accelerate the healing process — if they work. Because of increasing drug resistance, there's a chance a patient will just have a lot of unpleasant side effects.

The disease starts with a bite from a female sand fly infected with the Leishmania parasite, which the fly can pick up from people as well as infected animals like rodents and dogs. "That's a little painful — more than a mosquito [bite]," Acosta-Serrano says. (Although the fly itself is only about a third the size of a typical mosquito.)

The agony has only just begun. An infection appears at the site and soon develops into an open ulcer. Often, it's a large, disgusting (although painless) ulcer, notes Acosta-Serrano, who has seen the sores take over a person's entire cheek. After months (or even years), the skin eventually heals. But the person can be left with disfiguring scars, he says, which might make it difficult to get a job or find a spouse.

To avoid a worst-case scenario, some people attempt to self-vaccinate, Acosta-Serrano says. The technique — known as "leishmanization" — involves purposely infecting someone's leg by using material from the open ulcer of a person with CL. It can make the recipient immune to getting the disease again in a more unsightly spot. ("It's done to young girls because if they get a scar on their face, it's likely they'll get stigmatized and it's unlikely they'll get married in the future," he says.)

But it's a dangerous strategy, he says. It can lead to a severe bacterial or Leishmanial infection. Plus, it doesn't always work.

In an ideal world, a safe, commercially available vaccine would be on the horizon. It's not.

So Acosta-Serrano is appealing to wealthier countries to pitch in with more immediate forms of assistance. One way to decelerate the outbreak is to improve living conditions for refugees. Better sanitation reduces sand fly breeding. Sleeping indoors under nets reduces the risk of being bitten. Another item on the wish list: a fast, accurate and cheap diagnostic test that doesn't require an expensive laboratory setup.

The longer it takes for these things to happen, the more CL will spread. "This is urgent," says Acosta-Serrano, who hopes raising awareness will make a difference.

In some ways, the message has backfired. There are people citing CL as a reason to keep refugees out of Europe, although Acosta-Serrano says no one needs to fear an outbreak in countries with resources to prevent CL (and where there aren't as many sand flies).

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