THE EBOLA VIRUS AND THE NARRATIVE OF THE PANDEMIC

SPANISH VERSION

Hello everyone, as we said in the previous NOTE, due to the international ALARM launched by WHO,  today we bring you a complete review of the updated EBOLA VIRUS: THE EBOLA VIRUS AND THE NARRATIVE OF PANDEMICS, mainly because the media and Social Networks are the CREATORS of waves of PANIC among the population, and NONE of the PREVIOUS ALERTS (HANTAVIRUS, MARBURG VIRUS AND MONKEYPOX), ended in a pandemic. Certainly the population, in view of what happened with the PANDEMIC of Sars-Cov-2 or COVID-19 worldwide, is HIGHLY SUSCEPTIBLE to these notices.

 1.) DEFINITION:

The VIRUS of EBOLA is a FILOVIRUS,  (just like the MARBURG VIRUS), a very lethal RNA virus, discovered in 1976 in Africa, which causes a SEVERE HEMORRHAGIC FEVER with high mortality and outbreaks mainly in sub-Saharan Africa (1,2).
 

 2.) HISTORY OF THE DISCOVERY OF THE EBOLA VIRUS:

The EBOLA VIRUS was first identified in 1976, during two nearly simultaneous outbreaks that occurred in in present-day Democratic Republic of the Congo (DRC), in the village Yambuku, near the Ebola river, and in the areas of Nzara and Maridi in Sudan; from the first outbreak described near the river Ebola, came the name by which it has been known until today (1,3).

Since its discovery multiple outbreaks (more than twenty) have been described in various African countries, highlighting the major epidemic of 2014-2016 in West Africa, which became the largest event in number of cases and deaths reported (3,4).

3.) FIRST OUTBREAK EBOLA VIRUS, CHRONOLOGY:

 
The first documented outbreak of the disease caused by the virus Ebola was recorded in 1976 and constitutes a central milestone in the history of VIRAL HEMORRHAGIC FEVERS in Africa and in global public health (1,3). 

That year there were in fact two distinct but nearly simultaneous outbreaks: 

A- One in then Zaire, today the Democratic Republic of the Congo (DRC), in the village of Yambuku near the Ebola river.

In the Yambuku outbreak, in present-day Democratic Republic of the Congo, approximately 318 cases were reported, most of them initially linked to a missionary hospital, and reuse of medical supplies without proper sterilization, which favored nosocomial transmission (1,3). 

The clinical course of patients was characterized by a sudden onset of fever high, intense malaise and, in numerous cases, progression to hemorrhagic manifestations and multiple organ failure, making it one of the episodes with the highest lethality recorded for this disease (1,3,4).   

B- The other in Sudan, now South Sudan, in the localities of Nzara and later Maridi; the disease was named after the river near the Congolese focus, that is to say Ebola  (1,3,4).   

The Sudan outbreak originated in the city of Nzara and later spread to Maridi, significantly affecting factory workers and their close contacts, with about 284 people sick in total (2,3), with mortality somewhat lower than in the outbreak that occurred in Congo, but still with major social and health impact (2,3,4).

 Both outbreaks occurred in countries with poor health systems, which made early diagnosis and the immediate application of containment strategies difficult (1,2,3)

IN SUMMARY :

Overall, it is estimated that both outbreaks in 1976 had about 600 cases, with approximately 430 to 440 deaths, with a mortality in the outbreak of ZAIRE of 88 to 90% and in the SUDAN outbreak of 53 to 55%, reflecting the aggressiveness of the virus and the high vulnerability of the affected populations at that time (1,3,4). 

 These outbreaks prompted an intense INTERNATIONAL response, to determine the causal agents, animal reservoirs and routes of transmission  (1–4), highlighting the following patterns from an epidemiological point of view:

- Initial outbreak of cases in a community or health institution.

 - Spread through unsafe medical practices or family care without protection.  

- Funeral rituals with direct contact with the bodies of the victims (1,3,4), facts taken into account today for the future detection of new epidemics: 

- isolation protocols, use of personal protective equipment, and surveillance systems  (1–4).  

 DETECTION OF THE VIRUSES:

Despite the diagnostic limitations of the time, virological analyses made it possible to differentiate the viruses involved in each country:

1.) ZAIRE EBOLAVIRUS, and 

2.) SUDAN EBOLAVIRUS,  with different genetic characteristics and lethality levels (1,2,3,5). 

This taxonomic differentiation has been important and key to understanding why some outbreaks cause very high mortality rates, while others present somewhat lower lethality, which has made it possible to develop epidemiological approaches, different treatments, and vaccines depending on the type of virus in a given outbreak  (1–4). 

The Zaire outbreak in 1976 was very DEADLY, because a HIGHLY aggressive virus encountered hospitals with low infrastructure, reused syringes, high-risk funeral practices and a total absence of isolation protocols, therefore most cases ended in death before receiving minimal care (1,2,3,4,5).  

FIRST OUTBREAKS OF THE EBOLA VIRUS 1976:

YEAR	COUNTRY / LOCATION	APPROX. NUMBER OF CASES	APPROX. NUMBER OF DEATHS	APPROX. MORTALITY
1976	DRC (Yambuku, Ebola River)	~318	~280	88–90%
1976	Sudan (Nzara–Maridi)	~284	~151	53–55%
TOTAL		~602 CASES	~431 DEATHS	~71.6%

 

4.) VIROLOGICAL CHARACTERISTICS AND TAXONOMIC CLASSIFICATION:

The EBOLA VIRUS is a single-stranded RNA virus of negative sense, non segmented and enveloped, with characteristic filiform morphology, belonging to the group of viral HEMORRHAGIC FEVERS (2,3). Taxonomically it is included in the family FILOVIRIDAE and in thegenus EBOLAVIRUS, within which several species or variants have been recognized, which differ in geographic distribution, pathogenicity and lethality (2,3).

The main species described are: 

 

1.) ZAIRE EBOLAVIRUS (EBOV): associated with historically most lethal outbreaks; Zaire ebolavirus was first identified in 1976 in Yambuku, in the current Democratic Republic of Congo, (DRC), in the first outbreak of HEMORRHAGIC FEVER by Ebola. Throughout the years thousands of cases have been documented in different outbreaks Central and West Africa. It is considered the most lethal of all variants, with a mortality rate between 40 - 90%. It infects both primates and humans  (1,3). 

 2.) SUDAN EBOLAVIRUS (SUDV):  It was also described in the first outbreak of 1976, in Nzara y Maridi (then Sudan, today South Sudan), also with manifestations of HEMORRHAGIC FEVER, with elevated mortality. This variant also caused numerous cases, with a lower lethality than the Zaire variant Ebolavirus, ranging between approximately 40% and 60%.. It also infects humans and primates (1,3).

 3.) BUNDIBUGYO EBOLAVIRUS (BDBV):  Described by first time in 2007 in the district of Bundibugyo, in Uganda, during an outbreak of several hundred confirmed or suspected cases. The mortality of this variant is located  in a 30%, affecting both humans and primates, considering the degree of infection from moderate to high in humans (1,3).

 

4.) TAI FOREST EBOLAVIRUS (TAFV):  It was detected in 1994 in the forest of Tai, in Côte d'Ivoire, associated with the infection ofprimates primarily,  and to a number very reduced of human cases documented (one or few cases). The mortality in humans has not been well quantified due to the low number of cases, but in wildlife it can cause significant disease (3,4)

 

 

5.) RESTON EBOLAVIRUS (RESTV): This species was identified mainly in primates  and pigs, in the region of Reston Virginia United States in 1989, with pathogenicity, very low or null in humans (2,3,5). The virus was detected during an outbreak of disease HEMORRHAGIC in macaques cynomolgus imported from Philippines to quarantine installation to be studied, and no clinical cases severe in exposed humans. In all studied events no were confirmed clinical pictures of disease by Ebola in humans(5,7),only asymptomatic or subclinical infections; therefore the mortality in humans by this virus is 0%.  while in primates it can be high and in pigs mild or subclinical. (2,3).

VARIANTS OF EBOLAVIRUS

EBOVARIANT	COUNTRY / LOCATION	YEAR	NUMBER OF CASES	MORTALITY	INFECTION DEGREE (HUMAN / ANIMAL)
Zaire ebolavirus (EBOV)	Yambuku, DRC	1976	Thousands of cases in several outbreaks	40–90% (average ~50%)	High: very lethal in humans and primates.
Sudan ebolavirus (SUDV)	Nzara, Sudan (today South Sudan)	1976	Several hundred cases	40–60%	High: very pathogenic in humans and primates.
Bundibugyo ebolavirus (BDBV)	Bundibugyo, Uganda	2007	Few hundred cases	~30%	Moderate: pathogenic in humans and primates.
Tai Forest ebolavirus (TAFV)	Tai Forest, Côte d'Ivoire	1994	Very few cases (1–2)	Low / not well quantified	Low–moderate in humans; affects wildlife.
Reston ebolavirus (RESTV)	Reston, Virginia, USA (monkeys from Philippines)	1989	0 severe cases in humans; only in primates and pigs	0%	High in primates; very low or asymptomatic in humans; mild in pigs.

Brief Notes:

 

Virus: Zaire, Sudan, Bundibugyo and Tai Forest: produce disease by the virus of Ebola in humans, with variable lethality according to lineage and outbreak.

Virus: Reston: does not cause disease clinical in humans, but yes high mortality in monkeys and infection in pigs, so its degree of infection in animals is high; in humans cases subclinical.

 

5.) RESERVOIRS OF EBOLA VIRUS:

 

 

The natural reservoir of EBOLA VIRUS HAS NOT BEEN CONFIRMED definitively, but scientific evidence indicates that FRUIT BATS of the family "PTEROPODIDAE" are the main natural hosts of the virus (1,2,3,20). Specifically, three (3) species of BATS have been identified as possible reservoirs: 

1.) HYPSIGNATHUS MONSTROSUS 

(hammer-headed bat).

2.) EPOMOPS FRANQUETI.

SOURCE: WIKIPEDIA

3.) MYONYCTERIS TORQUATA.

SOURCE: GBIF.ORG

In these three bats have been found antibodies against the EBOLA VIRUS and viral genetic material (RNA), although the complete virus HAS NOT BEEN isolated conclusively in these species (1,14,15).

 

 

The virus is believed to persist in these bats as an ASYMPTOMATIC OR SUBCLINICAL INFECTION, without causing apparent disease, and is transmitted to other animals or humans under certain circumstances, such as changes in the environment, stress, alterations in food sources or during reproduction (14,15). 

6.) TRANSMISSION, INCUBATION PERIOD AND CONTAGION MECHANISMS: Transmission from the animal reservoir to humans, or between humans usually occurs by:

A.- Direct contact with blood, secretions, organs or bodily fluids of infected bats.

B- Indirectly through other animals that have been infected, such as primates (gorillas, chimpanzees, monkeys), forest antelopes and other mammals, handling and consumption of undercooked bushmeat or "bushmeat" (1,2,3,4,14,16).

 

 

C- Human outbreaks generally begin when a person enters in contact with an infected animal (live or dead) in tropical forest areas of Central and Eastern Africa, regions where the habitats of these reservoir species are found (1,2,3,4,14,20).

D- HUMAN to HUMAN transmission, occurs by contact with sick patients and their secretions: blood, vomit, diarrhea, saliva, sweat, semen, urine, breast milk or other bodily fluids, doctors and nurses in charge of caring for patients, by indirect contact with surfaces, clothing, sheets, medical material or contaminated needles (1,2,4); also through FUNERAL RITUALS, and preparation of corpses. 

 

 Considering the latter;BURIAL PRACTICES (contact with corpses and terminal patients), by family members and embalmers, the MAIN MECHANISM of contagion between humans and amplification factor (1,2). In contrast, the disease is not transmitted by air under usual community conditions nor by drinking water, nor has transmission been demonstrated by arthropod vectors such as mosquitoes (1,4).

 

 Despite advances in research, the Ebola reservoir remains the subject of ACTIVE STUDY, particularly to better understand how and when the virus reactivates and is transmitted from wild animals to humans, key information to prevent future outbreaks (1,14,15).

 

 Various epidemiological studies have shown that many animals of wildlife have been in contact with the virus of Ebola, which suggests that in addition to the mentioned bats other animal hosts could participate in transmission (14,15,17). 

 

 

7.) CLINICAL SYMPTOMS AND DISEASE EVOLUTION BY EBOLA VIRUS:

 

 

The disease by EBOLA VIRUS presents as a HEMORRHAGIC FEVER viral acute of sudden onset, which usually begins with general nonspecific symptoms and can progress to multiorgan involvement and shock (1,2). In the INITIAL PHASE, patients develop fever, intense headache, myalgias and generalized arthralgias , great asthenia, sore throat and general malaise, which can be confused with other frequent febrile infections in endemic regions (1,4).

 

In SUBSEQUENT PHASES appear profuse vomiting and diarrhea, intense abdominal pain, maculopapular rash and signs of coagulation alteration such as ecchymosis, petechiae and bleeding from mucous membranes, along with alteration of renal and respiratory function (1,4). The evolution towards hypovolemic shock, multiorgan failure and dehydration severe is the most frequent cause of death in fatal cases, especially when access to treatment of support is limited or late (1,4).

 

The rate of OVERALL CASE FATALITY of the disease by EBOLA VIRUS is located around the 50%, although it varies widely according to the causal species, the outbreak and the availability of medical care, with ranges going approximately from 25% to figures close to 90% in some outbreaks of ZAIRE EBOLAVIRUS (EBOV) (1,4).