EBOLA AND MARBURG VIRUSES
The Ebola and Marburg viruses are known as filoviruses. Since the 1960s, they have been the source for approximately 20 outbreaks. Both viruses have been prepared as biological weapons and cause great concern because of the extreme virulence and high mortality rates associated with infection.
The clinical course differs among patients, but often includes fever, rash, and encephalitis. Symptoms usually occur rapidly, and with both viruses, the course of the illness often progresses rapidly to profound hemorrhage, organ destruction, and shock. The mortality rate approaches 90%. When patients survive, the recovery period is often prolonged, with weakness, malaise, and cachexia common.
Despite aggressive research, the natural reservoirs for filoviruses have not yet been found, but it is thought that humans are in-fected only incidentally after exposure to an unrecognized host or by insect bite. Human-to-human transmission usually occurs after exposure to blood or other body fluid. When transmission is percutaneous, it appears that a very low inoculum of contam-inated blood is required for transmission to occur. The virus can also be spread by mucous membrane exposure. Although air-borne transmission does not appear to be a likely mode of transmission, the possibility has not been entirely eliminated. All involved in caring for patients with filoviruses must adhere to strict infection control measures. It is advisable that systems be set up to have objective monitors to ensure that each nurse or other health care worker wears complete protective equipment in the form of cap, goggles, masks, gown, gloves, and shoe covers.
Because there have been no cases diagnosed in the United States, it is likely that early signs of disease may be initially mis-classified. The diagnosis should be considered in a patient who has a febrile, hemorrhagic illness after traveling to Asia or Africa or who has handled animals or animal carcasses from those parts of the world. Because neither hospital nor local public health labo-ratories would be able to confirm a diagnosis, the CDC should be contacted immediately when Ebola and Marburg viruses are suspected to be the cause of illness.
No antivirals have been approved or show promise against Ebola and Marburg. Treatment is largely supportive maintenance of the circulatory system and respiratory systems. It is likely that the infected patient would need ventilator and dialysis support through the acute phases of illness.
Supportive care for a patient with such a devastating disease requires psychological support for the patient and family. The natural fear of an untreatable, aggressive disease would likely be intensified because of the rarity of the disease. The patient, his family, health care workers, and others in the community will need substantial, coordinated education about the known and unknown elements. Intervention may be required from those trained to provide psychological support for traumatic or terrorist events.
In March 2003, the World Health Organization issued a global warning about the appearance of a newly recognized type of pnemonia, Severe Acute Respiratory Syndrome (SARS). SARS is an influenza-like disease, with patients presenting with fever and cough. A minority will progress to experience respiratory distress. The disease was first recognized in China, with a second genera-tion of cases erupting quickly in Hong Kong, Vietnam, and over 17 other countries in a number of weeks.
The pattern of worldwide dissemination was largely attributed to travel because of strong epidemiologic evidence that patientsfrom many countries had shared common exposures. SARS serves as an example of how suddenly benign microorganisms, es-pecially viruses, can mutate to become important human pathogens. The epidemic illustrates important principles of pub-lic health and infection control. Before the disease came to the at-tention of the WHO, transmission to nurses and other health care professionals occured frequently. Once patients were appropri-ately isolated, with health care workers using barrier precautions and cleaning contaminated surfaces carefully, transmission was ef-fectively reduced or prevented.