Abstract

Ebola virus disease is a severe, often fatal illness that originates in wild animals and is transmitted to humans and other primates. The virus spreads through direct contact with the blood, secretions, organs or other bodily fluids of infected people.

 

Introduction

Ebola virus disease (EVD) is a severe, often fatal illness that originates in wild animals and is transmitted to humans affecting humans and other primates (WHO, 2020a). The virus spreads within the human population through direct contact with the blood, secretions, organs or other bodily fluids of infected people, and with surfaces and materials contaminated with these fluids (WHO, 2020a).

The average EVD case fatality rate is around 50%. Case fatality rates have varied from 25% to 90% in past outbreaks (WHO, 2020a). The first EVD outbreak was in 1976 near the Ebola River in Democratic Republic of Congo (DRC) (Kourtis et al., 2015), see Figure 1, and fruit bats of the Pteropodidae family are thought to be natural Ebola virus hosts (WHO, 2020a). Over the past 40 years, more than 20 outbreaks have been identified in sub-Saharan Africa, Figure 1 (Kourtis et al., 2015; Malvy et al., 2019), with more than 21 000 cumulative confirmed cases with greater than 8500 deaths as of January 20, 2015 (Kourtis et al., 2015).

Figure 1: Outbreaks of EVD in sub-Saharan Africa between 1976 and 2018 ( Malvy et al., 2019)

Microorganism Description

The genus Ebolavirus is composed of single-stranded, enveloped, filamentous RNA viruses, that, together with the Marburgvirus genus, comprise the family Filoviridae (Kourtis et al., 2015). EVD is a hemorrhagic fever virus and its manifestation include coagulation defects, capillary leak and shock (Kourtis et al., 2015). There are currently 5 species in the Ebolavirus genus namely; Tai Forest ebolavirus, Sudan ebolavirus (SUDV), Zaire ebolavirus (Ebola virus, EBOV), Bundibugyo ebolavirus and Reston virus (RESTV) (Kourtis et al., 2015).

Transmission

EVD is a biosafety level 4 pathogen and requires special containment measures and barrier protection, particularly for health care workers (Rewar and Mirdha, 2014). According to Rewar & Mirdha,(2014) EVD can survive in liquid or material for days and the incubation period is usually 4 to days but can be as short as 2 days and as long as 21 days. EVD transmits by direct contact with infected fruit bats or primates and infected persons’ (dead or alive) blood, secretions, tissues, organs, needles, syringes, and other bodily fluids (including urine, saliva, sweat, faeces, vomit, breast milk, and semen), however, airborne transmissions have not been documented (Rewar and Mirdha, 2014).

Pathogenicity

EVD runs its course within a period of 14 to 21 days and the patient may have nonspecific flu-like symptoms including fever, myalgia and malaise (Sullivan, Yang and Nabel, 2003). Sullivan et al., (2003) states that as time passes the infected patients start showing symptoms of severe bleeding and coagulation abnormalities, including gastrointestinal bleeding, rash, and a range of haematological irregularities, such as lymphopenia and neutrophilia. Exaggerated inflammatory responses that are not protective result from Cytokines which are releases when reticuloendothelial cells encounter EVD (Sullivan, Yang and Nabel, 2003). Vascular integrity is compromised once microvascular endothelial cells are infected by EVD (Sullivan, Yang and Nabel, 2003). Sullivan et al., (2003) states that hypotensive shock accounts for many EVD deaths and diffuse bleeding is observed in patients during the final stages of EVD.

Signs and Symptoms

WHO, (2020) states that several diagnostic tests have been developed to confirm the presence of EVD as it is hard to differentiate with other diseases that have similar symptoms such as malaria, typhoid, fever and meningitis. EVD symptoms include:

Fever,
Fatigue,
Muscle pain,
Headache,
and sore throat (WHO, 2020a).

EVD symptoms that follow include:

Vomiting,
Diarrhoea,
Rash,
Symptoms of impaired kidney and liver function
and in some cases, there may be internal and external bleeding (WHO, 2020a).

Treatment and prevention

WHO, (2020) states that there is no proven treatment for EVD but chances of survival are increased with early diagnosis and interventions, for example, rehydration with fluids and body salts and treatment of specific symptoms. WHO, (2020) further states that hand hygiene is the most effective way to prevent the spread of EVD and an experimental EVD vaccine (rVSV-ZEBOV) has proven to be highly preventative in a major trial that took place during a 2015 major trial in Guinea.

EVD outbreaks in the DRC 2018-2020

Figure 2 contains the EDV number of cases between 2018 and 2019 in the DRC by the week of onset and health zones (Kalenga et al., 2019) and a total of 1600 cases and 1069 deaths were registered in the DRC as of May 7, 2019, resulting in the case fatality rate of 67% (Kalenga et al., 2019). Kalenga et al., (2019) further state that out of all the cases registered, 57% (907) were female and 30% (475) were children.

On July 28, 2018, the EDV outbreak was registered in North Kivu and towards the end July 2018 it spread northwards to the Ituri province but was further contained around August 2018 (Kalenga et al., 2019). In August 2018, the virus was brought eastwards by infected people to Beni and in September 2018, it further spread from Beni south to Butembo and Katwa (Kalenga et al., 2019).  The 2020 EDV outbreak with a case fatality ratio of 66%, as of April 10, 2020, had 3456 confirmed and probable cases and 2276 deaths (WHO, 2020b). Compared to the Marburg hemorrhagic fever (Marburg HF) outbreak between the year 1998 and 2000 in the DRC, which had a case fatality rate of 83%, EDV has fewer fatalities (CDC, 2014). Malaria has the highest deaths yearly in the DRC followed by lower respiratory infections (CDC, 2019).

Figure 2: EDV number of cases between 2018 and 2019 in the DRC by the week of onset and health zones  (Kalenga et al., 2019)

 

EVD outbreak control measures

Madhav et al., (2018)  states that there are fewer data sources available on cost and cost-effectiveness on pandemic preparedness and response measures. Furthermore, measures put in place for early detection and mitigation are generally low cost, as costs incurred during hospitalization will generally be greater.

Low-cost EVD outbreak control measures in place include:

Surveillance,
Contact tracing,
Screening,
Vaccination,
Public awareness initiatives.

High-cost EVD outbreak control measures in place include:

Laboratory diagnosis,
Safe and dignified burials,
Case management, and
Infection prevention and control.

Kalenga et al., (2019) states that surveillance methods have been toughened up over time in the DRC and 88 to 92% of a 1000 alerts reported are investigated within the first 24 hours. Kalenga et al., (2019) further states that time taken to get an official report is still relatively long as the investigation of alerts and specimen testing have a turnaround time of 6 days. Contact tracing is also used to try and minimize the spreading of the virus by isolating and treating contacts that were exposed to the patients. Kalenga et al., (2019) states that it is a relatively hard process to manage as some patients have very long lists, some hide and refuse to subject themselves to follow-up tests, and others may have travelled too long distant places. The screening was conducted in high-risk areas where more than 200 000 people per day were screened at 80 points of entry and control (Kalenga et al., 2019). Post-exposure vaccination with rVSV-ZEBOV-GP commenced on August 8, 2018, and was carried out in high-risk areas, with about 112, 485 people vaccinated by May 7 2019, (Kalenga et al., 2019). Kalenga et al., (2019) states that most of the patients that died from EVD were given safe and dignified burials, furthermore minimal handling of the corpses, disinfection and allowing the religious and cultural proceedings to take place in a confined area. Attempts were made to continuously decontaminate facilities where cases were identified and to ensure health care facilities and key sites are well equipped with the training, infection prevention and control equipment, including essential hygiene products, such as chlorine, detergents, soap and water (Kalenga et al., 2019).  Kalenga et al., (2019) states that case management is done at the EVD treatment centres where supportive care is given to the patients, which includes aggressive rehydration, electrolyte imbalance correction, and nutritional support. Furthermore, Kalenga et al., (2019) state that on November 24, 2018, three antibody-based therapies (MAb114, ZMapp, and REGN-EB3)  and one antiviral agent (Remdesivir) were used. Lastly, risk communication, community engagement, and social mobilization were done to encourage greater local participation and ownership of initiatives to curb the EVD outbreak (Kalenga et al., 2019).

Conclusion

Marburg HF outbreak between the year 1998 and 2000 in the DRC, which had a case fatality rate of 83%, EDV has fewer case fatalities of about 66% in 2020 outbreak, The top 3 causes of death in the DRC include, malaria in the first position, lower respiratory infections in the second position and neonatal disorders. EDV is regarded as a biosafety level 4 disease and to control the EDV outbreaks effectively, low-cost measures should be strengthened, which includes; surveillance, contact tracing, vaccination and public awareness initiatives.

References

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