The research and observation of infected people as well as experiments in monkeys made it possible to develop a model of the infection course. The incubation period of the disease is from 2 to more than 20 days. Usually, the initial symptoms of hemorrhagic fever can be confused with malaria or diseases caused by bacteria, for example with typhoid fever, shigellosis, cholera, or colibacillosis. The disease generally begins with high fever accompanied by chills, arthralgia, and muscle, abdomen, and chest pain. Nausea and loss of appetite also may appear. After about 5 days, lumpy rash appears on the skin, which transforms after 1 day into large confluent limited lesions of the spotted-follicular character. They may also assume a hemorrhagic form. As a result of distorted of blood vessels integrity, bleeding arises from the nose, vagina, gums, and bloody vomiting, hemoptysis, or tarry stools may appear. Later on, Ebola virus affects the nervous system causing headache, agitation/fatigue, confusion, or even coma. Sometimes, it is possible to reign in the further development of the disease and the healing occurs approximately 2 weeks after the first symptoms. The vast majority of patients infected with Ebola virus die on the 7–16th day of the clinically developed disease. Multiple organ failure is an immediate cause of death associated with a decrease in arterial blood pressure and progressive tissue necrosis (Feldmann and Geisbert 2011; Jaax et al. 1996).

The properly taken medical history is the basis for diagnosis, with particular emphasis on the journeys made recently and the contact with wild animals (bats and primates). The isolation of the virus from specimens taken from the patient confirms the diagnosis.

There are several methods for detection of Ebola virus. The presence of the virus in the material is confirmed by the occurrence of the cytopathic effect in cell culture of human adrenocortical cancer. This study gives 100 % certainty of its presence. Breeding and serotyping are not widely used because of a high risk of infection of laboratory workers and the requirement of a class 4 safety laboratory (BSL4) (Gonzalez et al. 2007). Transmission electron microscopy is another method which allows for detection of viral particles in the blood and body fluids of the patient as well as of nucleocapsids (resulting from multiplication of the virus in the cytoplasm of infected cells). The use of this method, and also of the classic breeding method (Gear et al. 1978), requires a well-equipped laboratory, which makes it hardly available in African countries where the disease is endemic. Skin immunoassay is another sensitive, specific, and safe method. It is used to test skin samples taken from the deceased persons. Viral antigens are detected in the skin using monoclonal antibodies. The test can be carried out even on the skin preserved with formalin (Bwaka et al. 1999). Other available methods include immunoenzymatic assays (ELISA) based on the detection of viral antigen and anti-EBOV antibodies. The presence of antibodies may be confirmed by indirect immunofluorescence, radioimmunoprecipitation, or western-blots (Ksiazek et al. 1992). Currently, the best way to confirm the infection is to use molecular biology techniques with a variety of modified PCR, which allows for detection of Ebola virus nucleic acid. These techniques enable to detect RNA in mononuclear blood cells of infected patients, even before symptoms arise.

Due to high infectivity of the virus and the lack of effective vaccines and drugs, it is paramount that the principles of non-specific prevention be applied, i.e. isolation of patients, blocking the roads of the infection spread, equipment sterilization, the absolute use of goggles, gloves, aprons, and masks with HEPA filters.

There has so far been no known effective treatment for hemorrhagic fever caused by Ebola virus. Symptomatic treatment includes the use of analgesics and antipyretics. The loss of fluids, electrolytes, and blood and plasma clotting factors is supplemented in the event of bleeding diathesis. In case of severe infection, all the above described methods remain, unfortunately, little or no effective and may at best delay death for a few days (Ksiazek et al. 1999; Zaki et al. 1999). Experimental trials have included treatments with convalescent serum and human interferon in combination with IgG taken from a horse, goat, or hyperimmune sheep. These methods tested in various animals have turned out effective only for guinea pigs and mice (CDC 2001; Zaki et al. 1999). It is difficult to determine the effectiveness of these methods in human therapy, because promising results have been obtained only in a small number of patients. Recent studies have reported the ability of cyanovirins to slow down the development of viruses. Cyanovirins connect with the cell membrane and inhibit the viral entry into cells (WHO 1978). Another promising method of therapy appears to be the use of siRNA (small interfering RNA), which is responsible for silencing the activity of RNA polymerase. However, the beneficial therapeutic effect has been obtained only in non-primate mammals (Mupapa et al. 1999).

The following types of vaccines were experimentally tested in animals:

The Ebola virus is extremely virulent and contagious. Apart from obvious direct inoculation, like monkey’s bite or contact with body fluids and excretions of infected persons, experimental studies confirmed that transmission of Ebola infection may take place via oral or conjunctival routes (Jaax et al. 1996). Aerosol droplets have been less certain as a possible route of infection transmission. Recently, however, transmission of Ebola virus has also been validated for the aerosol (Johnson et al. 1995). Airborne droplets carrying viruses can easily gain access to mucosal membranes of conjunctivas or upper and lower respiratory tract. Therefore, it is highly probably that the epithelial layer of the respiratory tract may also be the entry way for the Ebola virus. The pulmonary route of infection has since long been pondered due to reports of catching the infection ‘at a distance’, without having direct contact. Jaax et al. (1995) have reported unexpected infection and death of two rhesus monkeys housed about three meters away from monkeys infected with Ebola virus. This kind of infection was substantiated in later studies in which the infection was transmitted from purposely inoculated pigs to macaques that were moved to the pig pen, even though the two species remained physically separated (Weingartl et al. 2012 and Weingartl 2011). Likewise, Kobinger et al. (2011) have reported virus transmission from infected to naive pigs, when the latter were put into the same living space, albeit remained physically separated. Further, the predominant feature of the infection in both reports was the involvement of the respiratory tract, ending up with fulminant interstitial pneumonia. Such observations give credence to the possibility of airborne transmission of the Ebola virus. Such transmission has recently been verified by Reed et al. (2011) who infected monkeys with Zaire Ebola virus by inhalation. The animals died and the courses of infection after inhalational and parenteral inoculation of the virus were alike. It seems that Ebola virus is an omnipotent virus capable of initiating infection through a variety of entry ways into the susceptible host and a variety of cell types. The Ebola virus, as any other virus, is totally dependent on living cells and only can it replicate in such cells. Thus, the skin which is covered the stratum corneum consisting of a layer of dead cells filled with keratin constitutes seemingly an impenetrable barrier for the virus. That may be illusory, since all too often microabrasions, invisible by naked eye, make corneocytes pervious to viruses. The extremely high risk level of infection with Ebola virus is a compelling reason to use the most elaborate protection gear, particularly in the health care setting.