Reemerging Ebola haemorrhagic fever 2014 and the risks of its introduction into Brazil

Abstract

Reemerging Ebola haemorrhagic fever 2014 and the risks of its introduction into Brazil The Ebola virus was identified in 1976 during epidemics of haemorrhagic fever in southern Sudan and northern Zaire (now the Democratic Republic of the Congo). The average mortality rate of Ebola virus disease, formerly known as Ebola haemorrhagic fever, is around 50% with rates varying from 25-90% in past outbreaks. The chronology of the outbreaks of the disease in different countries since 1976, according to the virus subtypes, numbers of cases and notified deaths up to November 2014 can be seen in Table. In this latest epidemic, eight countries have been affected: Guinea, Liberia and Sierra Leone have been the most affected countries while cases have been recorded in Nigeria, Senegal, United States of America (USA), Spain and Mali. A separate, unrelated Ebola outbreak occurred in Boende, Equateur, an isolated part of the Democratic Republic of Congo in August-October 2014. Filoviral diseases are caused by viruses of the family Filoviridae, which is composed by the Marburg, Cueva and Ebola viruses. Filoviruses are particles formed by long filaments that contain a single strand of RNA and they cause haemorrhagic fever in humans and non-human primates (monkeys, gorillas and chimpanzees). Given the lethal nature of these viruses, they are considered to be class IV pathogens, i.e., highly dangerous. Five subtypes of the Ebola virus have been identified: Zaire Ebola virus, Reston Ebola virus, Sudan Ebola virus, Tai Forest Ebola virus and Bundibugyo Ebola virus (Figure). The Zaire, Sudan and Bundibugyo subtypes have been responsible for major outbreaks of the disease. On the other hand, although the Reston and Tai Forest subtypes may affect human beings, no cases of fever and death among humans have been notified. The hosts of the Ebola virus are fruit-eating bats of the family Pteropodidae. Introduction of the virus into the human population occurs through close contact with blood, secretions, organs and other fluids from infected animals such as chimpanzees, gorillas, fruit-eating bats, monkeys, wild antelopes and wild pigs that are found sick or dead in the rainforests. The Ebola virus is transmitted among human beings through direct contact by means of lacerated skin or mucosa, with blood, secretions, organs and other body fluids from infected individuals or by means of materials and clothing that have become contaminated with these fluids. Healthcare professionals (physicians, nurses, pathologists and researchers) often become infected when they are treating patients with suspected or confirmed Ebola virus infection, through direct contact. A total of 558 healthcare workers are known to have been infected in the current outbreak of which 337 have died (data up to 21 November 2014). Furthermore, laboratory accidents and research activities on the virus in human beings and animals may give rise to the risk of infection, when precautions are not rigorously maintained. Individuals remain infected with the virus in their blood and b...