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Center of Excellence for Emerging and Zoonotic Animal Diseases

Pathogen of the Month



December pathogen of the month:


What is it? Ebola is a deadly viral disease that affects primates – including people, monkeys, gorillas and chimpanzees. It is caused by any of four varieties of the ebolavirus.

It is endemic in Africa, mostly within the Congolese forest basin

Symptoms include fever, headache, muscle pain, weakness, fatigue, diarrhea, vomiting and abdominal pain. Those symptoms may appear any time from two to 21 days following contact with the virus and often evolve toward a severe hemorrhagic syndrome, and death in half the cases.

Scientists hypothesize that bats are the reservoir host for the virus in the tropical rainforests of Africa, and that they transmit it to other animals, commonly apes but also occasionally antelopes. Humans can also acquire the virus by direct contact with infected bats or other infected animals.


History: The Centers For Disease Control says Ebola virus was discovered in 1976 near the Ebola River in what is now the Democratic Republic of Congo (DRC) in central Africa.

Since then there have been 21 outbreaks, including an ongoing outbreak that began this past May in the DRC. Scientists now believe the virus long pre-dated the first known outbreak, with risk factors such as population growth, encroachment into forested areas and direct interaction with wildlife contributing to its occurrence and spread within human populations.

The 2014 outbreak is probably the best known because it transcended the boundaries of tropical Africa, reaching as far as Italy, Spain and the United States. In the U.S., four imported cases were reported with one fatality. Most of the infected parties acquired the virus during overseas travel in tropical Africa. No secondary cases were reported in the U.S.



Map of ebola outbreaks by species and size since 1976

Mode of transmission. Ebola is most commonly spread to people via direct contact with the bodily fluids of a sick person. It can also be spread through direct contact with the blood, bodily fluids or tissues of infected fruit bats or primates. Sexual contact can also facilitate transmission, including contact with people who seem to have recovered from the disease, but who are convalescing long-term.

The CDC says that ebola is not usually transmitted by ingestion, although it is believed that, in some areas of the world, it can be transmitted by the handling and skinning of bushmeat via close contact with infected bodily fluids.

Ebola is not known to be transmitted by mosquitoes or ticks.


What is the current status? The current outbreak is on-going in the North Kivu and Ituri provinces of Congo. The most recent report identified 372 confirmed cases and 47 probable cases involving 240 deaths and 123 cures. Fifty-nine suspected cases were listed as under investigation.

Experimental vaccines and treatment have been apparently successfully during the present outbreak. However, since the outbreak is located in an active conflict zone, healthcare providers are faced with a number of other challenges that make fighting the outbreak.


Can livestock be affected by ebola? Scientists believe that pigs are the only species of livestock with the potential to be affected by ebolavirus. However that particular form of infection is not considered a threat to people, and has not been reported outside of a laboratory setting. Dogs eating dead infected animals appear to resist infection and develop antibodies.


What is CEEZAD doing? Dr. Jean-Paul Gonzalez, CEEZAD’s deputy director, is part of a team sponsored by the U.S. government that identifies personnel and methods capable of responding to the present outbreak in the DRC. Dr. Gonzalez and his team identified for the first time chiropterans as a potential carrier of ebolavirus. They also demonstrated the natural circulation of the ebolavirus antigen without outbreak occurrence in Central Africa. During the 2014 outbreak in Sierra Leone, he also took part of the ebola early response team in Sierra Leone.


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Sources: CEEZAD, Centers for Disease Control, webmd.com, promedmail.org