Emerging diseases are either outbreaks of newly appeared diseases, known diseases that are extensively growing in incidence or geographic range, or diseases that have only recently been identified as a separate pathogen-induced disease (National Institutes of Health, 2007). Emerging diseases include Lassa fever, gastric ulcers, cholera, hemolytic uremic syndrome, and Ebola virus disease (EVD). Re-emerging diseases are diseases that were once under control and have reappeared after a considerable decline in incidence (National Institutes of Health, 2007). Re-emerging diseases include malaria, cryptosporidiosis, rubeola, tuberculosis, and rabies.
More on the latter example of emerging diseases, Ebola virus disease (EVD) is a viral hemorrhagic fever (VHF) caused by the Zaire ebolavirus (EBOV). First recognized as an emerging disease in 1977, this pathogen belongs to the genus Ebolavirus and is characterized by virulence, with up to 80% mortality rate among the infected (Malvy et al., 2019). The largest ever-recorded Zaire ebolavirus outbreak occurred in Western African countries, including Liberia, Sierra Leone, and Guinea, between 2013-2016, resulting in more than 28,000 cases of EVD and 11,000 deaths (Malvy et al., 2019). Historically, the disease is primarily endemic to regions of sub-Saharan Africa, particularly west and equatorial Africa.
The pathogen spreads by human-to-human transmission through contact with body fluids of people who are currently infected or have died from the disease, including blood, vomit, urine, sweat, and breast milk (Malvy et al., 2019). The symptoms may appear in three stages. The early febrile or mild stage develops during the first three days after the contact with the pathogen, with symptoms such as fever, weakness, and myalgia. This stage is followed by gastrointestinal involvement during the first three-to-ten days, with added symptoms such as diarrhea, vomiting, or abdominal pain. This stage might further escalate during the complicated phase within the first seven-to-twelve days since the onset of symptoms, including gastrointestinal involvement plus hypovolemia, hemorrhage, organ failure, encephalitis, and additional concurrent infections due to immune suppression.
Part of the high fatality rate is the absence of licensed Ebola-specific prophylaxis, vaccines, or treatment plan, making healthcare providers resort to symptomatic management of infected patients. The recommended care for hypoxemia caused by hypovolemia is oxygen therapy; for vomiting, antiemetic drugs; for severe pain and encephalitis are opiates; for concomitant infections are broad-spectrum antibiotics (Malvy et al., 2019). This symptomatic care involves the provision of supportive care during the first two stages or of critical care for a patient in the complicated stage.
References
Malvy, D., McElroy, A. K., de Clerck, H., Günther, S., & van Griensven, J. (2019). Ebola virus disease. Lancet, 393(10174), 936–948.
National Institutes of Health. (2007). Understanding Emerging and Re-emerging Infectious Diseases. National Institutes of Health.