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Monday, August 04, 2014
A Q&A with Dr. James Childs
Dr. James “Jamie” Childs is a zoonotic disease specialist at the Yale School of Public Health who worked on a previous outbreak of Ebola virus. The deadly disease is currently afflicting several countries in Africa (Guinea, Liberia and Sierra Leone) and has triggered fears that it could spread into territories where it has previously been unknown. Prior to coming to Yale, Dr. Childs worked at the Centers for Disease Control and Prevention and spent four weeks on the ground in Kikwit, Zaire (now the Democratic Republic of the Congo), in 1995 investigating an outbreak of the disease that killed 280 of the 318 people infected. Dr. Childs currently works on a range of other zoonotic diseases, including hantaviruses, arenaviruses, rabies and vector-borne, or environmentally transmitted bacteria, including rickettsia, borrelia and leptospira. He joined Yale in 2004.
Why is the Ebola virus so deadly?
JC: Ebola causes multisystem diseases with vascular involvement leading to overt bleeding under the skin, in internal organs, or from the mouth, eyes or ears. However, patients rarely die directly from blood loss, but show shock, nervous system, kidney or pulmonary malfunctions, coma, delirium, and seizures. The patho-physiologic causes of bleeding abnormalities vary with the etiologic agent and include endothelial cell tropism with attendant capillary leakage and disseminated intravascular coagulation.
Ebola viruses vary in their ability to cause human infection, disease and death. The five currently differentiated species in the genus Ebola virus (Family: Filoviridae) have different virulence for humans. The Zaire species of Ebola, currently circulating in West Africa causes mortality of up to 85 percent among humans, while the Sudan species causes mortality in the 50 percent to 60 percent range.
How is the virus transmitted?
JC: These are zoonotic agents, which circulate among bats in their natural maintenance cycle. Animals other than humans, most notably the great apes, are susceptible to infection and the fatal disease caused by Ebola viruses. In many instances we do not know the immediate source of exposure involving the index human case, but butchering meat obtained from a freshly dead chimpanzee has been directly linked to a small outbreak. Once a human is infected the virus can be directly transmitted to another human without the further need of reintroduction from the extra-human reservoir species. Close human-to-human contact is required for Ebola virus transmission as the virus is shed in body excretions, secretions and blood. There is no aerosol transmission, such as occurs with measles and influenza virus.
As the load of virus can be very high in blood and contaminated waste products, extreme caution and stringent barrier-protection techniques are essential when using needles or sharp instruments in the care of infected patients. Sexual transmission by infectious semen may be a rare occurrence after apparent recovery from infection.
What are its symptoms?
JC: The incubation period of Ebola hemorrhagic fever ranges from a few days to weeks. However, the onset of febrile disease is abrupt, prostrating, and often accompanied by severe headache and sore throat. Gastrointestinal complications with nausea, vomiting and diarrhea usually follow and high titers of virus are then present in the blood and feces. At this point laboratory examinations usually show low white blood cell and platelet counts and internal and external bleeding abnormalities are evident; a rash is sometimes present.
Too often an epidemic of Ebola virus begins in a hospital setting where physicians, nurses and technicians, lacking critical barrier protection or sterile equipment, are exposed to infectious bodily materials. Seemingly routine procedure on an Ebola patient presenting with early, non-readily differentiated symptoms can lead to multiple infections among attending health care workers. Disease can rapidly spread through health workers at a hospital with disastrous results including closures of hospitals and clinics. Patients must then be treated at home, usually by family members who, in turn, are at risk of becoming infected. Added to that is the difficulty of safely disposing of the highly infectious bodies of the recently dead.
One of the major challenges to effective control of Ebola virus is that the symptoms and signs of early infection cannot be readily distinguished from those associated with numerous parasitic diseases, such as malaria, or other viral infections afflicting persons in endemic regions of Central and West Africa.
What are the challenges to control Ebola virus in West Africa?
JC: Even in simpler settings than currently exist with the ongoing outbreak of Ebola virus in West Africa, where infection is widespread in both urban and rural locations, control requires scrupulous attention to epidemiologic details and planning for hospital management. Effective control of an Ebola epidemic involves case tracking, trace-backs of persons previously in contact with infected individuals, and quarantine of potentially exposed persons. In addition, safe treatment of currently infected patients requires the establishment of special, dedicated hospital wards staffed with experienced doctors, nurses and staff. All of this is much, much easier to say than to provide. Wards require proper isolation facilities with protocols for the decontamination and disposal of contaminated materials.
In communities where cases are occurring within households, rather than at any care facility, rapid identification and collection of the dead is critical and special safety precautions must be implemented. Well-trained and barrier-protected workers must decontaminate the site and the collected bodies prior to burial. New, large and separate gravesites might be required.
In many areas of West Africa ritual cleansing of the corpse prior to burial is a sacred/sacrosanct tradition. Irrespective of the risk posed to family members, it is difficult for authorities and public health officials to intercede on established cultural customs. Public health education by multiple media sources is essential to inform individuals on how and which close contacts lead to transmission, but the effective delivery of any such message in an environment charged with fear, distrust and increasing social stigmatization is challenging to say the very least. When suspicion of local officials and Western medical and public health interventions is high, and there have been attacks on local health missions during this outbreak, the abandonment of established cultural practices with little evidence of tangible benefit is a hard sell.
Where is Ebola virus found?
JC: Only one Ebola virus species, Reston virus, has been identified outside Africa in the Philippines. This species has never been associated with a human death. The other four known species are limited to central and western Africa.
Is there a significant danger of it spreading beyond these areas?
JC: Yes, almost certainly. There are few indications that the human-to-human transmission has been effectively contained in many locations, but this is an area of the world with limited resources to spend on health care, little to no surveillance and epidemiologic capacity and a dearth of trained professionals able to cope with the details of patient management and required safety procedures. Health care priorities and infrastructure in most African countries are already strained dealing with the problems of known endemic diseases, such as malaria. Planning for an outbreak of a relatively rare but highly fatal disease such as Ebola unfortunately must take a backseat.
The spread of Ebola to other countries in West Africa and elsewhere is a major concern. There are certainly concerns that the virus will be introduced into Western nations, especially if infection takes hold in a country like Nigeria, but with the epidemiologic and medical infrastructure available in countries such as the United Kingdom or the United States the risk of an introduction leading to an epidemic is vanishingly small.
Country borders are always porous. Quarantine of specific locations within a country or between countries may provide some benefits—if only to public perception. All viruses can travel by airplane and recently an infected Liberian traveled to Nigeria prior to dying of Ebola. As this outbreak shows no signs of being controlled, most neighboring nations are presumably planning contingency measures should Ebola be introduced.