Primary prevention
The following preventive measures are recommended for people in an area affected by an outbreak:[78]
Practice careful hygiene (e.g., wash hands with soap and water, alcohol-based hand sanitizer, or chlorine solution)
Avoid contact with body fluids of people who are sick and do not handle items that have come into contact with an infected person's body fluids (e.g., clothes, medical equipment, needles)
Avoid contact with semen from a man who has recovered from Ebola virus infection, until testing confirms the virus is no longer present
Avoid funeral or burial rituals that require handling of the body of someone who has died from confirmed or suspected Ebola virus infection
Avoid contact with nonhuman primates, forest antelopes, and bats, including body fluids or raw meat prepared from these or unknown animals
Returning travelers (including healthcare workers) should follow local policies for surveillance and monitor their health for 21 days and seek medical attention if symptoms develop, especially fever.
Healthcare workers who may be exposed to infected patients should follow these steps:
Wear protective clothing
Practice proper infection control and sterilization measures
Isolate suspected patients from each other if possible, and confirmed patients from suspected patients
Avoid direct contact with bodies of people who have died from confirmed or suspected infection. During epidemics, direct contact with any dead body should be avoided
Notify health officials if you have direct contact with the body fluids of an infected patient.
If infection is suspected based on initial screening, immediate isolation is warranted before any further workup is carried out. This is crucial to reduce contact with other patients and healthcare workers while the patient is being investigated. Isolation measures should be continued until the patient has tested negative.[79]
The highest risk facing healthcare workers when looking after infected patients is inadvertently touching their own faces or neck under the face shield during patient care, and removing (doffing) personal protective equipment (PPE). Healthcare workers should understand the following basic principles of using PPE:[79]
Donning: PPE must be donned correctly in proper order before entry into the patient care area. Since PPE cannot be modified while in the patient care area, caution should be taken to ensure it is as comfortable as possible before entering the area. No skin should be exposed. Donning activities must be directly observed by a trained observer, and a final check performed before entering the patient care area
During patient care: PPE must remain in place and be worn correctly for the duration of exposure to potentially contaminated areas. PPE should not be adjusted during patient care. Healthcare workers should perform frequent disinfection of gloved hands using an alcohol-based hand rub or chlorine solution, particularly after handling body fluids. If there is a partial or total breach in PPE (e.g., gloves separate from sleeves leaving exposed skin, a tear develops in an outer glove, a needlestick) during patient care, the healthcare worker must move immediately to the doffing area to assess the exposure and implement the facility exposure plan, if indicated. The immediate action drills to take in the event of a high-risk exposure (needle stick injury and mucous membrane splash) should be clear to all healthcare workers. After safe doffing, a rapid risk assessment and consideration of post-exposure prophylaxis (PEP) should be undertaken.[80]
Doffing: removal of used PPE is a high-risk process that requires a structured procedure, a trained observer, and a designated area for removal to ensure protection. PPE must be removed slowly and deliberately in the correct sequence to reduce the possibility of self-contamination or other exposure. A stepwise process should be developed and used during training and daily practice.[Figure caption and citation for the preceding image starts]: Healthcare worker in personal protective equipment at an Ebola treatment center in Sierra Leone, 2014From the personal collection of Chris Lane, MSc (Public Health England/World Health Organization); used with permission [Citation ends].
The importance of a "buddy" when inside the patient care area and during donning and doffing, to ensure safe practice cannot be overstated, together with guidance from independent monitors if available. CDC: the buddy system Opens in new window
The Centers for Disease Control and Prevention (CDC) and World Health Organization (WHO) produce detailed guidance on PPE:
CDC: personal protective equipment (PPE) Opens in new window
WHO: infection prevention and control guideline for Ebola and Marburg disease Opens in new window
Vaccines:
Ebola Zaire vaccine, live (Ervebo®)
Also known as rVSV-ZEBOV or rVSV∆G-ZEBOV-GP vaccine. It is a live attenuated vaccine which contains vesicular stomatitis virus that has been modified to contain a protein from the Zaire ebolavirus.
The World Health Organization (WHO) has prequalified the vaccine, and several African countries have approved it for the prevention of Ebola virus infection caused by Zaire ebolavirus. It is recommended by WHO’s Strategic Advisory Group of Experts (SAGE) on Immunization as part of a broader set of Ebola outbreak response tools.[81]
The Food and Drug Administration and the European Medicines Agency have approved the vaccine for the prevention of Zaire ebolavirus infection in at-risk individuals ≥1 year of age.
In the US, the Centers for Disease Control and Prevention’s Advisory Committee on Immunization Practices recommends pre-exposure vaccination for adults ≥18 years of age who are at highest risk for potential occupational exposure to Ebola virus because they are responding to an outbreak, work as healthcare personnel at a federally designated Ebola treatment center in the US, or work as laboratorians or other staff members at biosafety level 4 facilities in the US. It is also recommended for healthcare personnel involved in the care and transport of patients with suspected or confirmed Ebola virus infection at special pathogens treatment centers, and people who work in Laboratory Response Network facilities that handle specimens that might contain replication-competent Ebola virus (Zaire ebolavirus) in the US.[82] The vaccine is not currently commercially marketed in the US, but is currently stockpiled in the Strategic National Stockpile and is made available through the Centers for Disease Control and Prevention.[83]
The vaccine is administered as a single intramuscular dose. Common adverse reactions include injection-site reactions, arthralgia, myalgia, rash, headache, fever, and fatigue.
Pregnant and breast-feeding women should be offered vaccination with the Ebola Zaire live vaccine during an active outbreak caused by Zaire ebolavirus in affected areas, in the context of rigorous research or in accordance with a compassionate use protocol, with informed consent.[84]
The Sierra Leone Trial to Introduce a Vaccine against Ebola (STRIVE) trial, a combined phase II and III clinical trial to assess the safety and efficacy of rVSV-ZEBOV, found that no cases of Ebola were reported in the 7998 participants who were vaccinated.[85] An open-label, cluster-randomized, ring vaccination trial in which contacts of a suspected Ebola case were vaccinated with a single intramuscular dose of rVSV-ZEBOV was conducted in Guinea. Patients in the treatment arm received the vaccine immediately, while vaccination was delayed by 21 days in the control arm. The study found that rVSV-ZEBOV has a high protective efficacy. No patients who received the vaccine developed Ebola virus infection 10 days or more after randomization in the immediate-treatment arm; however, cases occurred in unvaccinated patients in the comparison group.[86]
Ad26.ZEBOV/MVA-BN-Filo vaccine (Zabdeno®/Mvabea®)
Uses a prime-boost strategy to enhance immunogenicity and involves the use of two distinct viral vectors that are administered as different doses. The Ad26.ZEBOV component of the regimen is a monovalent vaccine based on adenovirus serotype 26 vector (Ad26) expressing the EBOV glycoprotein, and is designed to provide active specific acquired immunity to the Zaire ebolavirus. The MVA-BN-Filo component of the regimen is a multivalent vaccine based on modified vaccinia Ankara (MVA) vector expressing EBOV, Sudan virus, and Marburg virus glycoproteins and Tai Forest virus nucleoprotein, and is designed to provide immunity to the Sudan ebolavirus, Zaire ebolavirus, Tai Forest ebolavirus, and the Marburg virus.[87]
The European Medicines Agency has approved the vaccine for the prevention of Zaire ebolavirus infection in children ≥1 year of age and adults. The vaccine has been authorized under exceptional circumstances, and is not appropriate for an outbreak response where immediate protection is necessary. This vaccine has not been approved in the US as yet.
The vaccine is administered as a 2-dose heterologous course, given 8 weeks apart. Common adverse reactions include injection-site reactions, arthralgia, myalgia, headache, fever, and fatigue.
There are no data on the use of Ad26.ZEBOV/MVA-BN-Filo vaccine in pregnancy; however, vaccination should not be withheld when there is a clear risk of exposure.
Phase 3 trials are either completed and not published as yet, or ongoing.
ChAd3-ZEBOV vaccine
An experimental chimpanzee-derived adenovirus vector with an Ebola virus gene inserted that is still in early-stage trials. A randomized, placebo-controlled phase II trial found that an antibody response to vaccination with ChAd3-ZEBOV or rVSV-ZEBOV was observed in 71% to 84% of active-vaccine recipients versus 3% of placebo recipients by 1 month. Responses were largely maintained at 12 months.[88]
Other vaccines are in development.
Secondary prevention
Ebola virus infection is a notifiable disease.
If infection is suspected, the patient should be put in isolation and all healthcare workers in contact with the patient should wear personal protective equipment. The Centers for Disease Control and Prevention (CDC) and World Health Organization (WHO) produce detailed guidance on infection prevention and control in healthcare settings:
CDC: personal protective equipment (PPE) Opens in new window
WHO: infection prevention and control guideline for Ebola and Marburg disease Opens in new window
Contact tracing (e.g., family, friends, work colleagues) is essential. People who have been exposed to the Ebola virus within the last 21 days and who are asymptomatic need to be monitored for the duration of the incubation period in order to ensure rapid recognition of symptoms followed by immediate isolation. The WHO has produced guidance on contact tracing:
Healthcare workers suspected of being infected should be isolated and treated the same as any other patient until a negative diagnosis is confirmed.[153] If exposure to body fluids from a patient with suspected infection has occurred, the person should immediately wash affected skin surfaces with soap and water and irrigate mucous membranes with copious amounts of water.
Safe burial practices are essential but are not always culturally accepted, and this continues to be a challenge.[75]
Post-exposure prophylaxis (PEP):
This is a rapidly changing field.[212] A useful framework that takes a stratified approach to exposure risk has been proposed.
PEP is recommended in high-risk patients (e.g., people with broken skin or mucous membrane contact with an infected patient (alive or deceased) or their body fluids, a penetrating sharps injury, or contact with contaminated gloves or clothing). It may also be considered in patients with intact skin-only contact with an infected patient (alive or deceased) or their body fluids. Options to consider include passive immunotherapy with monoclonal antibodies (e.g., ZMapp, MIL77), antiviral agents (e.g., favipiravir, remdesivir, BCX4430), or vaccination (e.g., rVSV-ZEBOV) depending on specific patient circumstances.[213]
In addition to these interventions, psychologic support is needed for healthcare workers exposed to dangerous pathogens.[214]
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