Monday, October 13, 2014

Infectious Disease in the News Pt. I: Ebola

Ebola is caused by infection with one of five filovirus strains, a type of single-stranded RNA virus.  It can be transmitted to people from wild animals and further spreads via human-to-human transmission, causing severe, often fatal disease in humans and non-human primates.  Although its natural reservoir is unknown, fruit bats have been implicated. 

Ebola was first discovered in 1976 near the Ebola River in the Democratic Republic of the Congo. Over the years, sporadic outbreaks have occurred in remote African villages.  The current outbreak was first reported in March 2014.  It is the largest in history, involving both rural and urban areas in multiple countries in West Africa, and has been designated the first Ebola epidemic the world has ever known. Human-to-human transmission occurs via direct contact (through broken skin or mucous membranes) with blood, and other bodily fluids (e.g. saliva, stool, semen, breast milk) of infected people.  Contaminated surfaces and materials such as clothing and bedding also serve as sources of infection.     

Previously known as Ebola hemorrhagic fever because of the internal and external bleeding that can occur, the illness has an incubation period between exposure and the onset of clinical illness that ranges from 2-21 days.  Humans are not infectious until they develop symptoms which typically mimic a flu-like illness with the sudden onset of fever, fatigue, muscle pain, headache and sore throat. This is followed by vomiting, diarrhea, rash, impaired kidney and liver function, and in some cases bleeding.  Leukopenia (low white blood cell counts), thrombocytopenia (low platelet counts), and elevated liver enzymes can be seen.   A definitive diagnosis can be made using specialized testing of blood samples (e.g. ELISA, RT-PCR, electron microscopy or cell culture) under maximum biological containment conditions. 

The average case fatality rate is ~50%, though can be as high as 90%.   There are no specific, proven therapies or vaccines for Ebola, though several health workers have been treated with ZMapp, an investigational product comprised of three humanized monoclonal antibodies.  There is also interest in empirically transfusing convalescent whole blood or plasma from patients who have recovered to patients with early Ebola disease.  Supportive care may improve survival, but this unfortunately is lacking in many African countries.  Gowns, gloves, masks and goggles or face shields should be worn by healthcare personnel and family members caring for ill patients, and hand washing should occur often. These have also been in short supply in Africa and strict infection control practices have been lacking. 

Current CDC recommendations for individuals who may have had contact with ill patients include isolation (staying at home and avoiding public contact) and monitoring daily temperatures and symptoms for 21 days to detect any potential illness as quickly as possible.  


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