Ebola hemorrhagic fever (Ebola virus disease) facts

• Ebola hemorrhagic fever is a disease caused by four different strains of Ebola virus; these viruses infect humans and nonhuman primates. It is also referred to as Ebola virus disease.
• Ebola hemorrhagic fever has a short history since it was discovered in 1976. There have been a few outbreaks, including the current (April 2014) "unprecedented epidemic" in Africa.
• Symptoms and signs of Ebola virus disease include an incubation period of two to 21 days, starting with abrupt fever, headache, joint and muscle aches, sore throat, and weakness; progression of symptoms include diarrhea, vomiting, stomach pain, hiccups, and rash with more devastating symptoms of internal and external bleeding in many patients.
• Ebola viruses are mainly found in primates in Africa and possibly the Philippines; there are only occasional outbreaks of infection in humans. Ebola hemorrhagic fever occurs mainly in Africa in the Republic of the Congo, Gabon, Sudan, Ivory Coast, and Uganda, but it may occur in other African countries.
• Ebola virus can be spread by direct contact with blood and secretions, by contact with blood and secretions that remain on clothing, and by needles and/or syringes used to treat Ebola-infected patients.
• Risk factors for Ebola hemorrhagic fever are travel to areas with endemic Ebola hemorrhagic fever and/or any close association with an infected person.
• Early clinical diagnosis is difficult as the symptoms are nonspecific; however, if the patient is suspected to have Ebola, the patient needs to be isolated and local and state health departments need to be immediately contacted.
• Definitive diagnostic tests for Ebola hemorrhagic fever are ELISA and/or PCR tests; viral cultivation and biopsy samples may also be used.
• There is no standard treatment for Ebola hemorrhagic fever; only supportive therapy is available.
• There are many complications from Ebola hemorrhagic fever; the prognosis for patients ranges from fair to poor since many patients died from the disease (death rate equals about 25%-100%).
• Prevention of Ebola hemorrhagic fever is difficult; early testing and isolation of the patient, plus barrier protection for caregivers (mask, gown, goggles, and gloves), is very important to prevent others from getting infected.
• Researchers are trying to understand the Ebola virus and pinpoint its ecological reservoirs to better understand how outbreaks occur. Researchers are actively trying to establish an effective vaccine against Ebola viruses by using several experimental methods, but there is no vaccine available currently.

 

Picture of the Ebola virus

What is Ebola hemorrhagic fever?

Ebola hemorrhagic fever is a viral disease caused by Ebola virus that results in nonspecific symptoms early in the disease and often causes internal and external hemorrhage (bleeding) as the disease progresses. Ebola hemorrhagic fever is considered one of the most lethal viral infections; the mortality rate (death rate) is very high during outbreaks (reports of outbreaks range from about 50% to 100% of humans infected, depending on the Ebola strain).

What is the history of Ebola hemorrhagic fever?

Ebola hemorrhagic fever was first noted in Zaire (currently, the Democratic Republic of the Congo or DRC) in 1976. The original outbreak was in a village near the Ebola River after which the disease was named. During that time, the virus was identified in person-to-person contact transmission. Of the 318 patients diagnosed with Ebola, 88% died. Since that time, there have been multiple outbreaks of Ebola virus, and five strains have been identified; four of the strains are responsible for the high death rates. The four Ebola strains are termed as follows: Zaire, Sudan, Tai Forest, and Bundibugyo virus, with Zaire being the most lethal strain. A fifth strain termed Reston has been found in the Philippines. The strain infects primates, pigs, and humans and causes few if any symptoms and no deaths in humans. Most outbreaks of the more lethal strains of Ebola have occurred in Africa and mainly in small- or medium-sized towns. Once recognized, African officials have isolated the area until the outbreak ceased. However, in this new outbreak that began in Africa in March 2014, some of the infected patients have reached larger city centers and have been hospitalized. Unfortunately, many people may have been exposed to the virus in the city, thus causing more infections (and deaths). This outbreak in Africa has now spread to Guinea's capital and has been detected in the neighboring countries of Liberia and Sierra Leone. About 122 infected people have been diagnosed and 78 have died as of Apr. 1, 2014. The infecting Ebola virus detected this outbreak is the Zaire strain, the most pathogenic strain of Ebola. Health agencies are terming this outbreak as an "unprecedented epidemic."

What causes Ebola hemorrhagic fever?

The cause of Ebola hemorrhagic fever is Ebola virus infection that results in coagulation abnormalities, including gastrointestinal bleeding, development of a rash, cytokine release, damage to the liver, and massive viremia (large number of viruses in the blood) that leads to damaged vascular cells that form blood vessels. As the massive viremia continues, coagulation factors are compromised and the microvascular endothelial cells are damaged or destroyed, resulting in diffuse bleeding internally and externally (bleeding from the mucosal surfaces like nasal passages and/or mouth and gums and even from the eyes [termed conjunctival bleeding]). This uncontrolled bleeding leads to blood and fluid loss and can cause hypotensive shock that causes death in many Ebola-infected patients.

Picture of the Ebola virus, viewed with an electron microscope; SOURCE: CDC/Frederick Murphy

What are risk factors for Ebola hemorrhagic fever?

The risk factors for Ebola hemorrhagic fever are travel to areas where Ebola infections (see current CDC travel advisories for African countries) have been reported. In addition, association with animals (mainly primates in the area where Ebola infections have been reported) is potentially a risk factor according to the CDC. Another potential source of the virus is eating "bush meat." Bush meat is the meat of wild animals, including hoofed animals, primates, and rodents. Currently, evidence for any airborne transmission of this virus is lacking. During Ebola hemorrhagic fever outbreaks, health-care workers and family members and friends associated with an infected person are at the highest risk of getting the disease. Researchers who study Ebola hemorrhagic fever viruses are also at risk of developing the disease if a laboratory accident occurs.

What are Ebola virus disease symptoms and signs?

Unfortunately, early symptoms of Ebola virus disease are nonspecific and include the following: fever, headache, weakness, vomiting, diarrhea, stomach discomfort, decreased appetite, and joint and muscle discomfort. As the disease progresses, patients may develop other symptoms and signs such as a rash, eye redness, hiccups, sore throat, cough, chest pain, bleeding both inside and outside the body (for example, mucosal surfaces, eyes), and difficulty breathing and swallowing. Ebola virus disease symptoms and signs may appear from about two to 21 days after exposure (average is eight to 10 days). It is unclear why some patients can survive and others die from this disease, but patients who die usually have a poor immune response to the virus.

How do physicians diagnose Ebola hemorrhagic fever?

Ebola hemorrhagic fever is diagnosed preliminarily by clinical suspicion due to association with other individuals with Ebola and with the early symptoms described above. Within a few days after symptoms develop, tests such as ELISA, PCR, and virus isolation can provide definitive diagnosis. Later in the disease or if the patient recovers, IgM and IgG antibodies against the infecting Ebola strain can be detected; similarly, studies using immunohistochemistry testing, PCR, and virus isolation in deceased patients is also done usually for epidemiological purposes.

What is the treatment for Ebola hemorrhagic fever?

According to the CDC and others, standard treatment for Ebola hemorrhagic fever is still limited to supportive therapy. Supportive therapy is balancing the patient's fluid and electrolytes, maintaining their oxygen status and blood pressure, and treating such patients for any complicating infections. Any patients suspected of having Ebola hemorrhagic fever should be isolated, and caregivers should wear protective garments. Currently, there is no vaccine or specific treatment for Ebola hemorrhagic fever.

What are complications of Ebola hemorrhagic fever?

Ebola hemorrhagic fever often has many complications; organ failures, severe bleeding, jaundice, delirium, shock, seizures, coma, and death (about 50% to 100% of infected patients). Those patients fortunate enough to survive Ebola hemorrhagic fever still may have complications that may take many months to resolve. Survivors may experience weakness, fatigue, headaches, hair loss, hepatitis, sensory changes, and inflammation of organs (for example, the testicles and the eyes).

What is the prognosis of Ebola hemorrhagic fever?

The prognosis of Ebola hemorrhagic fever is often poor; the death rate of this disease ranges from about 50% to 100%, and those who survive may experience the complications listed above.

Is it possible to prevent Ebola hemorrhagic fever? Is there a vaccine for Ebola hemorrhagic fever?

The main way to prevent getting Ebola hemorrhagic fever is to not travel to areas where it is endemic and by staying away from any patients who may have the disease. Medical caregivers may protect themselves from becoming affected by strict adherence to barriers to the virus (wearing gloves, gowns, goggles, and a mask). Currently, there is no vaccine available against the Ebola virus strains that cause Ebola hemorrhagic fever in humans.

What is the latest research on Ebola hemorrhagic fever?

Research on developing a vaccine against Ebola viruses is ongoing; successful vaccines have been developed that work in experimental animals (mice and guinea pigs but not against macaques monkeys). With new and larger outbreaks of Ebola hemorrhagic fever possible, researchers are intensely working to develop an effective vaccine utilizing genetically modified viruses, recombinant viruses, and inactivated Ebola viruses. Unfortunately, none are currently available.

REFERENCES:

Samb, Saliou. "Scale of Guinea's Ebola epidemic unprecedented: aid agency." Reuters. Mar. 31, 2014. <http://www.reuters.com/article/2014/03/31/us-guinea-ebola-idUSBREA2U10E20140331>.

Sullivan, Nancy, Zhi-Yong Yang, and Gary J. Nabel. "Ebola Virus Pathogenesis: Implications for Vaccines and Therapies." Journal of Virology 77.18 Sept. 2003. <http://jvi.asm.org/content/77/18/9733>.

United States. Centers for Disease Control and Prevention. "Ebola Hemorrhagic Fever." Apr. 7, 2014. <http://www.cdc.gov/vhf/ebola/index.html>.

United States. Centers for Disease Control and Prevention. "Ebola Hemorrhagic Fever: Chronology of Ebola Hemorrhagic Fever Outbreaks." Apr. 7, 2014. <http://www.cdc.gov/vhf/ebola/resources/outbreak-table.html>.