Headlines - Ebola: Virus Transmission and the Concept of High-Risk Contacts

Two factors determine how dangerous an infectious agent is: its pathogenicity, on the one hand—that is, its ability to cause disease and potentially lead to death—and its transmissibility, on the other. In terms of pathogenicity, the Ebola virus is highly virulent because it causes severe symptoms (fever, diarrhea, vomiting, bleeding, kidney and liver failure, etc.) that can lead to multiple organ failure and the patient’s death, especially since there is no specific treatment for this infection. The case fatality rate of Ebola virus infections—that is, the proportion of deaths among those who become ill—is high: it ranges from 50% to 90% depending on the outbreak. In the current outbreak, which primarily affects three West African countries, between 30% and 60% of reported infected patients, depending on the country, have died (WHO data as of October 29, 2014). Transmission of the Ebola virus by an infected person, who is necessarily symptomatic, can occur from person to person or via a contaminated environment (surfaces): it requires direct physical contact with the bodily fluids (blood, secretions, etc.), tissues, or organs of an infected, sick person. However, the rapid deterioration of a sick person’s condition leads very quickly to their hospitalization, making it highly unlikely that this person would continue to engage in normal activities (such as going to work or visiting a public place). Consequently, the risk of transmission primarily concerns the healthcare staff caring for the patient, and, where applicable, family members who may have cared for the patient while they were symptomatic prior to hospitalization, during funeral arrangements, or at the time of burial.The difficulties currently encountered in West Africa in controlling the epidemic are largely due, on the one hand, to a lack of personnel and equipment to isolate and care for patients in hospitals and health centers, and, on the other hand, to the performance of funeral care and burials without protective equipment.