Ebola hemorrhagic fever (EHF),a severe, often-fatal rare disease of humans and nonhuman primates particularly monkeys, gorillas, and chimpanzees, is caused by Ebola virus, one of the most lethal viruses ever known. The first outbreak of the disease occurred in Nzara and Maridi villages, Southern Sudan in June, 1976, with 284 reported human cases and 151(53%) deaths. Three months later in September, another outbreak of the disease was reported in Yambuku (a village close to Ebola River, from where the virus derived its name), Democratic Republic of Congo (then Zaire), with 318 cases and 280(88%) deaths. After careful observation and laboratory analysis, it was discovered that the two outbreaks were caused by two antigenically and biologically distinct strains of Ebola virus and subsequently named Sudan Ebola virus (SEBOV) and Zaire Ebola virus (ZEBOV) respectively. The third strain of Ebola, Reston Ebola virus (REBOV), was first identified in 1989 when infected monkeys were imported into Reston, Virginia, USA, from Mindanao in the Philippines with, fortunately, no human casualty.
The two strains, SEBOV and ZEBOV, remained responsible for most of the outbreaks in Africa till 1994,when another set of out breaks erupted with increased frequency, leading to the discovery of two new distinct strains, namely Côte d’Ivoire ebola virus (CIEBOV) in 1994 in Tai Forest, Côte d’Ivoire, with one reported human case who survived the attack, and Bundibugyo ebola virus (BEBOV) in 2007 in Bundibugyo province, Uganda, with 149 cases and 137(25%) deaths.
SEBOV, ZEBOV, REBOV, CIEBOV, and BEBOV are therefore the only five strains of Ebola virus so far discovered to be responsible for Ebola haemorrhagic fever. However, while REBOV infection is restricted to monkeys, gorillas, and chimpanzees with no reported human casualty despite reported cases in the US, Phillipines and Italy, SEBOV and ZEBOV are responsible for most human outbreaks and high casualty figures in West and Central Africa. The recent outbreak (still on-going),described as the deadliest in the history of the virus, is attributed to ZEBOV and as of 16thJuly, 2014, the cumulative number of cases in three West African countries of Guinea, Liberia and Sierra Leone was put at 844,out of which518(61.4%) deaths had been confirmed. ZEBOV, with case fatality rates as high as 90%, indeed constitute a particularly serious threat in sub-Saharan Africa.
Ebola is one of three RNA viruses inthe family Filoviridae and genus Filovirus; so named because of their filamentous structure. The other two virusesare Marburg and Cueva, responsible for Marburg haemorrhagic fever (MHF) and Cuevahaemorrhagic (CHF) fever respectively. These three viruses are considered as the deadliest among all viruses incessantly harassing and threatening the existence of mankind. Other types of viral haemorrhagic fevers from other viral families include Rift Valley fever, Crimean-Congo haemorrhagic fever, Lassa fever, yellow fever, and dengue haemorrhagic fever.
Ebola is transmitted to humans through close contact with the blood, secretions, organs or other body fluids of infected animals such as chimpanzees, gorillas, fruit bats, monkeys, forest antelope and porcupines, found either ill or dead in the rainforest. The infection then spreads through human-to-human transmission to family members or health-care workers, directly through handling of blood, secretions, organs or other body fluids of infected people, and indirectly through environments and objects contaminated with such fluids. In addition burial ceremonies where mourners have direct contact with the infected body of the deceased person have also been reported to play a role in transmission of the virus. Possible sexual transmission has also been suggested since active Ebola was demonstrated in the semen of men who have recovered from clinical episodes of the disease up to7 weeks after recovery. Fruit bats (the common bat), particularly species of the genera Hypsignathusmonstrosus, Epomopsfranqueti and Myonycteristorquata, are considered possible natural hosts for the virus.
The incubation period is approximately 2 to 21 days after exposure to the virus. This is followed by sudden onset of fever, intense weakness, muscle pain, severe headache, vomiting, diarrhoea, and stomach pain, as well as loss of appetite, cold, cough, and sore throat. In terminal cases there maybe impaired kidney and liver function, chest pain, eye swelling, genital swelling (labia and scrotum), erythematous rash over the entire body, difficulty in breathing and swallowing, and both internal and external bleeding, accompanied by coma, shock and eventually death. While the reason why some people miraculously and surprisingly recover from Ebola attacks and others do not is not yet fully understood, it is assumed that those who die usually do not develop a significant immune response to the virus by the time their death occur.
In the absence of standard and accurate diagnostic procedures, symptoms of Ebola could be mistaken for that malaria, typhoid fever, cholera, meningitis, hepatitis and other viral haemorrhagic fevers. This has severally caused wrong treatment and preventive measures to be administered till the late hour, thereby leading to high casualty figures of the disease.
Currently there are no approved antiviral drugs or vaccines against Ebola virus. Thus, raising awareness of the risk factors for Ebola infection and the protective measures individuals can take is the only way to reduce human infection and death. It is also highly necessary to observe and maintain a good personal and environmental hygiene. In addition fevers or any of the primary symptoms already highlighted that have defied treatments for common ailments should be promptly reported to the nearest government health care agency. Finally, since the virus is zoonotic in origin, hunting, handling, cooking and consumption of bush meat should either be reduced to the barest minimum or completely stopped forthwith.
No case of Ebola has ever been reported in Nigeria. However there is an on-going outbreak which started in Guinea in February before crossing borders to Liberia and Sierra Leone, and recently, Ghana where one reported suspected case died in the first week of July. The threat of possible outbreak of Ebola in the country is therefore real and considering the porosity of Nigerian borders which has allowed Boko Haram to operate at will, it may not be too long before the country will record its first cases of the dreaded virus, unless the Nigerian factor is withdrawn completely and adequate quarantine surveillance systems are mounted to monitor influx of people and animals from neighbouring countries, especially those currently ravaged by the virus. The surveillance should however not be restricted to land borders alone but sea – and air – ports as well.
It will simply be too disastrous if Nigeria is confronted with two deadly attacks, one from bomb-loving Boko Haram and another from silent invading Ebola, at the same time.
Robert Obi, a Doctoral Student and member Virology Research Group, College of Medicine, University of Lagos, is a Lecturer at the Department of Microbiology, Federal University of Technology, Owerri