Ebola Death Toll in Congo Rises to 131

The death toll from the Ebola outbreak in the Democratic Republic of the Congo has risen to 131 from 513 suspected cases, health minister Samuel Roger Kamba said Tuesday. There has also been one death in neighboring Uganda, the Africa Centers for Disease Control and Prevention reported.

The head of the World Health Organization said he was "deeply concerned" about the outbreak. "Early on Sunday, I declared a public health emergency of international concern," Tedros Adhanom Ghebreyesus told the World Health Assembly in Geneva. "I did not do this lightly.

... This is only the third known outbreak of this virus, and there are no vaccines or treatments. Ebola disease is caused by orthoebolaviruses, of which there are multiple species. Three of the viruses have been known to cause large Ebola disease outbreaks, according to the WHO.

They are Ebola (or Zaire) virus, which has been the most common; Sudan virus; and Bundibugyo virus, the one identified in this outbreak. The only approved vaccine and treatments are for the Zaire strain. Because each virus species has different genetic material, they need different vaccines.

There are some other vaccines in development, but nothing that targets Bundibugyo virus is close to being ready for use, said Dr. Celine Gounder, a CBS News medical correspondent and infectious diseases specialist who deployed in the response to a past Ebola outbreak.

Before this outbreak, there were two known outbreaks caused by the Bundibugyo virus, and both were smaller than the current one. The first discovery of the Bundibugyo strain occurred in the Bundibugyo District in Uganda in 2007. There were 149 cases and 37 deaths in that outbreak, The Associated Press reported.

The second known outbreak was in Congo in 2012, with 57 cases and 29 deaths reported, according to the AP. Because there have been fewer outbreaks of this virus, there is far less data about how it behaves than for the Zaire virus, which has been around since 1976 and caused dozens of outbreaks, Gounder said.

Bundibugyo virus disease, the type of Ebola disease caused by the Bundibugyo virus, is severe and often fatal. The virus spreads from person to person through direct contact with bodily fluids of someone who is sick or has died from the disease. The early symptoms can often be mistaken for other illnesses, the WHO says.

They include fever, fatigue, muscle pain, headache and sore throat. Those can progress to other symptoms, including vomiting, diarrhea, abdominal pain, rash, organ dysfunction and internal or external bleeding. The fatality rate of Bundibugyo virus disease, based on the past two outbreaks, is about 30 to 50%, the WHO says.

While still highly deadly, this is lower than the fatality rate of the Zaire strain, which can be up to 90%. "Early intensive supportive care including rehydration and treatment of specific symptoms, can improve survival," the WHO says.