Experts warn that plague, a lethal disease of a bygone era, appears to be cropping up again, mostly in parts of Africa. They worry the illness is easily confused with other diseases and failure to recognize and treat the condition leads to rapid death. VOA's Jessica Berman reports.

The Black Death of medieval Europe, a type of plague, killed 20 to 30 million people before it was over 300 years later. Experts say plague is beginning to emerge as a health menace in Africa.

In a study published in the online journal, Public Library of Science (PLoS Medicine), the authors note the number of recent cases officially attributed to plague is not huge. Over the past 20 years, they say, between 1,000 and 5,000 cases, and 100 to 200 deaths, attributed to plague have been reported to the World Health Organization.

But there is concern that the number of cases is underestimated in countries where plague is cropping up, including Tanzania, Malawi, Mozambique, Uganda, the Democratic Republic of the Congo and Madagascar.

Kenneth Gage is with the division of Vector Borne Infectious Diseases at the U.S. Centers for Disease Control in Fort Collins, Colorado.

He says physicians often don't consider plague when patients get sick because many illnesses in Africa can have similar symptoms. Since there is no rapid blood test that can identify plague, doctors are left to guess, from the symptoms, whether someone is infected with plague.

Gage says the CDC started a project in a small area in Uganda to begin monitoring the number of plague cases.

He says researchers found a few hundred cases of plague per year plus a couple of suspected cases each month.

"That's not to say all those are plague but this is a small region of Uganda," said Kenneth Gage. "So, it leads you to believe that there's quite a bit of plague going on in Africa that we simply don't identify. The diagnostic capabilities of these rural clinics is very low and in most instances they couldn't diagnose plague from a laboratory standpoint and they may not know what the person died of."

Gage says people become infected with plague after coming in contact with wild rats carrying fleas that harbor the plague bacterium.

Gage says there can be decades between outbreaks, and he points to one on the outskirts of Oran in Algeria.

"They hadn't seen plague in that part of Algeria for more than 50 years," he said. "Then all of a sudden, they had an outbreak and it was a complete surprise. We believe the ecology of the region there, the habitats in some of the more mountainous areas, are more suitable for plague. So, it's not a surprise perhaps that it survived in the wild rodents. For whatever reason, it appeared to spill over in [to] the human population, and they had an actual outbreak. Plague can do that."

Experts say bubonic plague, called the Black Death, causes swollen, painful black bumps making it easier to identify than two other types of plague, one that affects the lungs and the other which causes internal bleeding.

If not treated quickly with antibiotics, plague can lead to death within days.