This document was developed by the AABB Clinical Transfusion Medicine Committee to provide information regarding Ebola virus disease (EVD) and precautions to be taken to control infection when collecting and handling blood specimens.
The ongoing Ebola outbreak in West Africa has raised questions within the transfusion medicine community in the developed world. Ebola viruses are a group of filoviruses first recognized in 1976, during outbreaks with separate strains named for their location of original origin, in Zaire (now the Democratic Republic of Congo (DRC)) and Sudan. Subsequent outbreaks have occurred in Sudan, Zaire/DRC, Ivory Coast, Gabon, Uganda and now in Liberia, Guinea, Sierra Leone and Nigeria. The infection begins as a non-specific febrile illness that can progress to hemorrhagic symptoms in some cases, with case fatality rates in sub-Saharan Africa of 25-90%, in part dependent on the strain.
Transmission occurs after direct contact with infectious blood and body fluids; it is not an airborne infection. The incubation period after exposure is 2-21 days, and, according to the Centers for Disease Control and Prevention (CDC), diagnosis by polymerase chain reaction (PCR) may not be reliable until 3 days after the onset of symptoms. Asymptomatic viremia is not known to occur and travelers from epidemic foci are deferred under current malaria screening guidance for US blood donors, so the likelihood of blood donation by viremic individuals is considered negligible. Transfusion transmission is not described and has not been alleged. Interest in the transfusion medicine community in the developed world has been stimulated by the risk that returning travelers may be incubating EVD and seek care when symptoms begin.
The observed risk of exposure and infection of healthcare workers in sub-Saharan Africa (under severely resource-constrained conditions) raises important questions for occupational safety, including in laboratories providing services for patients with, or suspected to have, EVD. There are insufficient published data about specific risks to laboratory personnel in the US, but several patients have been cared for safely in the US using standard laboratory precautions prior to the recognition that they were infected with a viral hemorrhagic fever. Ultimately, these patients were diagnosed with either Marburg or Lassa fever virus infection, and extensive follow-up studies of hundreds of contacts in hospitals where care was provided found no evidence of transmission to healthcare workers or laboratory staff.1
CDC interim guidance reproduced in the box below calls for clinicians to follow contact and droplet precautions and laboratory personnel to use the bloodborne pathogens standard to prevent transmission in health care settings from patients with or suspected to have EVD.2 The precautions are based on the known transmission characteristics of the pathogen.
Infection Control When Collecting and Handling Specimens
All laboratorians and other healthcare personnel collecting or handling specimens must follow established standards compliant with the OSHA bloodborne pathogens standard, which includes blood and other potentially infectious materials. These standards include wearing appropriate personal protective equipment (PPE) and following all safety rules for all specimens regardless of whether they are identified as being infectious.
Recommendations for risk assessment to staff: Risk assessments should be conducted by each laboratory director, biosafety officer, or other responsible personnel to determine the potential for sprays, splashes, or aerosols generated from laboratory procedures. They should adjust, as needed, PPE requirements, practices, and safety equipment controls to protect the laboratorian’s skin, eyes, and mucous membranes.
Recommendations for specimen collection by staff: Any person collecting specimens from a patient with a case of suspected Ebola virus disease should wear gloves, water-resistant gowns, full face shield or goggles, and masks to cover all of nose and mouth. Additional PPE may be required in certain situations.
Recommendations for laboratory testing by staff: Any person testing specimens from a patient with a suspected case of Ebola virus disease should wear gloves, water-resistant gowns, full face shield or goggles, and masks to cover all of nose and mouth, and as an added precaution use a certified class II Biosafety cabinet or Plexiglass splash guard with PPE to protect skin and mucous membranes. All manufacturer-installed safety features for laboratory instruments should be used.
Source: CDC. At http://www.cdc.gov/vhf/ebola/hcp/interim-guidance-specimen-collection-submission-patients-suspected-infection-ebola.html. Accessed 28 August 2014.
Some hospitals and public health authorities are developing infection prevention and control guidance that is more stringent than that from CDC. Some of them have specifically recommended that facilities forgo pretransfusion testing (type, antibody screen and crossmatch ) and use group O RBCs (and presumably “universal” platelets and plasma) for the transfusion needs of patients suspected or known to have EVD. This is to protect blood bank staff from exposure to potentially infectious material in the absence of published data quantitating the risk of transmission within clinical laboratories of developed nations, which are clearly safer than those in sub-Saharan Africa.
Conversely, there is concern that this approach will expose patients with alloantibodies to an unacceptable risk of receiving incompatible transfusions. It is highly likely that only a tiny proportion of suspect patients will have EVD; alternative diagnoses that may require advanced transfusion medicine support, including falciparum malaria or dengue fever, are likely to be much more common than EVD among travelers to and from sub-Saharan Africa.
CDC recommendations are permissive for pretransfusion testing given resources widely available.
A full range of clinical and epidemiologic information and guidance can be accessed at the following CDC link. Facilities should review this website frequently, as CDC will update it as more information becomes available. http://www.cdc.gov/vhf/ebola/index.html?s_cid=cdc_homepage_feature_001
1 Emerg Infect Dis. 2010 Oct;16(10):1598-600. Morb Mortal Wkly Rep. 2009 Dec 18;58(49):1377-81. Emerg Infect Dis. 2009 Aug;15(8):1171-5. Morb Mortal Wkly Rep. 2004 Oct 1;53(38):894-7.
2 While current concerns revolve around EVD, the procedures under discussion may be appropriate for any viral hemorrhagic fever and facilities may want to consider a broad set of prospectively developed policies and procedures to address this broader range of pathogens.