The first Ebola virus was discovered in 1976 near the Ebola River in the Democratic Republic of the Congo. Ebola virus causes viral hemorrhagic fever in humans and nonhuman primates such as monkeys, gorillas, and chimpanzees. Five subspecies of Ebolavirus have been identified. Four of the five have caused disease in humans: Ebola virus (Zaire ebolavirus); Sudan virus (Sudan ebolavirus); Ta� Forest virus (Ta� Forest ebolavirus); and Bundibugyo virus (Bundibugyo ebolavirus). The fifth, Reston virus (Reston ebolavirus), has caused disease in nonhuman primates, but not in humans.
A large outbreak of Ebola virus disease began in West Africa in March 2014. A total of 1848 cases and 1013 deaths have been reported in Guinea, Liberia, Sierra Leone and Nigeria as of August 9, 2014. The death rate is between 55 and 60%. Two U.S. healthcare workers in Monrovia, Liberia, have contracted Ebola virus infection.
Humans contact Ebola virus from infected wildlife. Bats are believed to be the natural reservoir. It is then spread person-to-person through direct contact with bodily fluids such as blood, urine, sweat, semen, and breast milk. The incubation period is usually 8-10 days, but can range from 2- 21 days. Patients can transmit the virus while febrile and through later stages of disease, as well as postmortem, when persons contact the body during funeral preparations.
During outbreaks of Ebola virus disease can spread quickly within health care settings when hospital staff is not wearing appropriate protective equipment such as masks, gowns, and gloves.
Ebola virus disease is characterized by sudden onset of fever and malaise, accompanied by other nonspecific signs and symptoms, such as myalgia, headache, vomiting, and diarrhea. Patients with severe forms of the disease may develop multi-organ dysfunction, including hepatic damage, renal failure, and central nervous system involvement, leading to shock and death.
The recent cases in a traveler and in healthcare workers demonstrate the risk for spread of Ebola virus in these populations. Additional information on Ebola virus disease can be found at: http://www.cdc.gov/ebola
Within a few days of symptom onset, the diagnosis can be confirmed by antigen capture enzyme-linked immunosorbent assay, Ebola virus IgM immunoassay or polymerase chain reaction (PCR). Later in the course of disease, testing for Ebola IgG and IgM antibodies is recommended.
CDC recommends testing for all persons with onset of fever within 21 days of having a high-risk exposure. A high-risk exposure includes any of the following:
- percutaneous or mucous membrane exposure or direct skin contact with body fluids of a person with a confirmed or suspected case of Ebola virus disease without appropriate personal protective equipment (PPE),
- laboratory processing of body fluids of suspected or confirmed Ebola virus disease cases without appropriate PPE or biosafety precautions, or
- participation in funeral rites or other direct exposure to human remains where an outbreak is occurring without appropriate PPE.
If a person has a high-risk exposure but does not exhibit a fever, testing is recommended only if other findings are present such as thrombocytopenia or elevated transaminases. Testing is recommended for persons with a low-risk exposure who develop fever, with or without other symptoms, and have abnormal lab test results
Persons with no known exposures who develop fever with other symptoms and abnormal lab tests within 21 days of visiting endemic countries should be considered for testing if no other diagnosis is found.
If testing is indicated, local or state health department should be immediately notified. Specimen requirement is a minimum of 4 mL of whole blood or plasma shipped refrigerated or frozen in accordance with IATA guidelines as a Category B diagnostic specimen.
CDC Health Alert Network, July 28, 2014, CDCHAN-00363
Guidelines for Evaluation of US Patients Suspected of Having Ebola Virus Disease,
CDC Health Advisory, CDCHAN-00364, August 1, 2014.