Ebola Virus

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); Taï Forest virus (Taï Forest ebolavirus); and Bundibugyo virus (Bundibugyo ebolavirus). The fifth, Reston virus (Reston ebolavirus), has caused disease in nonhuman primates, but not in humans.

The Zaire species of Ebola virus caused a major outbreak in Western Africa between 2014 and 2016. In 2022, the Ministry of Health in Uganda declared an Ebola outbreak caused by the Sudan species. The genetic sequences of these two strains differ by about 40 percent. 

Ebola virus outbreaks have been caused by direct human exposure to infected fruit bats or other animals. Bats are believed to be the natural reservoir. The virus can be spread person-to-person through direct contact with bodily fluids. The infectious dose of Ebola virus is as low as 1 to 10 virions and the incubation period is usually 8 to10 days but can range from 2 to 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.

Blood, feces and vomit appear to be the most infectious. Blood from an infected individual can exceed 10E8 viral particles per milliliter. Ebola virus has also been detected in breast milk, urine and semen. In a convalescent males, the virus can persist in semen for at least 70 days. Saliva and tears may also carry some risk of transmission, especially in severely ill patients. Live virus has not been isolated from sweat. There is no evidence that Ebola virus has mutated into a form that could cause airborne transmission. 

Ebola virus can also be transmitted indirectly by contact with previously contaminated surfaces and objects. 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. Risk of indirect transmission is low and can be reduced even further by appropriate cleaning and disinfection procedures.

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.

Health care workers should take a detailed travel and exposure history with patients who exhibit fever, severe headache, muscle pain, weakness, diarrhea, vomiting, stomach pain, unexplained hemorrhage. If the patient is under investigation for Ebola, health care workers should activate the hospital preparedness plan for Ebola, isolate the patient in a separate room with a private bathroom, and ensure standardized protocols are in place for PPE use and disposal. Health care workers should not have physical contact with the patient without putting on appropriate PPE.

Current screening criteria for Ebola virus disease include clinical and epidemiologic risk factors. Clinical criteria include fever and additional symptoms such as severe headache, muscle pain, vomiting, diarrhea, abdominal pain, or unexplained hemorrhage.

The following routine laboratory tests should be ordered on patients with travel associated illness:

• Complete blood count with differential
• Electrolytes, creatinine, BUN, and glucose
• Liver function tests
• Coagulation tests (PT, PTT, fibrinogen)
• Urinalysis
• Bacterial blood culture

Epidemiologic risk factors within the past 21 days before the onset of symptoms include: 

• Residence in, or travel to, an area where EVD transmission is active 
• Contact with blood, other body fluids or human remains of a patient known to have or suspected to have EVD
• Direct handling of bats, non-human primates, and other animals from disease-endemic areas Direct handling of unpreserved tissues from any of these animals.

If both clinical and epidemiological criteria are met, the patient should be moved to a private room with a bathroom, and STANDARD, CONTACT, and DROPLET precautions followed during further assessment. They should be immediately reported to hospital leadership and the state health department. 

Any laboratory event that produces a spill, splash, droplet, or aerosolization can potentially result in infection of laboratory staff. Even the removal of a specimen tube cap can create dangerous droplets. Routine testing that requires centrifugation should be avoided whenever possible unless it can be performed using closed tubes and sealed buckets or rotors. The use of whole blood point of care devices behind dedicated barriers is preferable. 

CDC issued its latest Lab Advisory: Guidance for Transport and Shipment of Specimens for Ebola Virus Testing on October 19, 2022. Before collecting specimens for Ebola testing, clinical laboratories must first contact their state health department. State health departments must consult CDC to determine if testing for Ebola virus is warranted.

If testing is needed, CDC will provide guidance on specimen collection and shipping instructions to select public health laboratories that are members of the Laboratory Response Network. Eleven public health laboratories within the laboratory response network (LRN) can perform Ebola testing for the Sudan strain. 

Ebola testing requires collection of two 4 mL plastic tubes of whole blood, collected in EDTA and shipped at 2 to 8^○ C. One specimen is shipped to the designated network laboratory for preliminary testing, and the other specimen is sent to the CDC for confirmatory testing.  While in the patient room, the treatment team member should wipe the outside of tubes with approved disinfectant and label tubes with a printed patient chart label, adding date/time of collection to the label. These samples are considered Category A infectious materials and should be packaged accordingly. 

At this time, there are no Food and Drug Administration (FDA) approved countermeasures such as vaccines or therapeutics for Ebola Sudan strain. In addition, there are not any FDA-approved rapid tests for the Sudan strain, but the FDA is currently in discussion with other federal agencies to address this issue.

Commercial carriers may or may not accept the shipment, depending on CDC classification of risk level for individual patients. Decisions are made on a case-by-case basis. State public health departments or CDC may assist in arranging for specimen transportation to their facility for testing. 

References

CDC, Guidance for U.S. Hospitals and Clinical Laboratories on Performing Routine Diagnostic Testing for Patients with Suspected Ebola Disease. https://www.cdc.gov/vhf/ebola/laboratory-personnel/safe-specimen-management.html 

Koepsell SA, et al. The role of the laboratory and transfusion service in the management of Ebola virus disease. Transfus Med Rev. 2017;31(3):149-53.