Health authorities in Liberia said they had now recorded eight suspected cases of Ebola, mainly in people who crossed the border from Guinea. Five of these had died but tests were still being carried out to check if the cases were indeed Ebola. The World Health Organisation (WHO) said a total of 86 suspected cases, including 59 deaths, had been reported in southeastern Guinea near the border with Sierra Leone and Liberia. Laboratory tests have confirmed 13 cases of Ebola in Guinea so far, the first outbreak of the disease in West Africa.
“People are really frightened. They have seen people die in a matter of just two or three days. They are constantly worried who is going to be the next fatality,” said Joseph Gbaka Sandounou, who manages operations for aid agency Plan International in Guekedou. “People have never experienced anything like this before. Rumors are rife among communities who are trying to come up with their own explanations.”
Samples taken from those who died in Liberia had been sent to Conakry for testing, according to the Geneva-based WHO. In Guinea, authorities have taken steps to quarantine suspected cases in the districts of Guekedou, Macenta, Nzerekore and Kissidougou.
In Sierra Leone, authorities set up a task force after the death of a 14-year-old boy who had attended the funeral of a suspected Ebola victim. Authorities have yet to confirm if the boy died of the disease.
Virulent strain
Ebola was discovered in 1976 in then-Zaire, now Democratic Republic of Congo. Scientists have identified the outbreak in Guinea as the virulent Zaire strain of the virus. Because people who fall sick with it tend to vomit, have diarrhea and suffer both internal and external bleeding, their bodies are often “covered in virus”, explained Peter Piot, one of the co-discoverers of Ebola and now director of the London School of Hygiene and Tropical Medicine.
This means anyone in close contact with them – such as nurses, doctors and carers – is at risk, he said. The virus causes a raging fever, headaches, muscle pain, conjunctivitis and weakness, before moving into more severe phases of causing vomiting, diarrhea and hemorrhages.
In the southeastern Guinea town of Macenta, prices – especially for products like chlorine – have risen due to shortages, resident Mamady Drame said. People have also started avoiding shaking hands. “Can you imagine that people are hesitant to even greet each other? That is a shocking symbol in our culture,” Drame said. In the distant capital, where there have not yet been any confirmed cases, some bank staff handling cash wore gloves and clients were encouraged to wash their hands before entering.
Esther Sterk, a tropical diseases specialist at medical charity Médecins Sans Frontières, said that while dangerous, Ebola remains rare. Since its 1970s discovery, around 2,200 cases have been recorded. Of those, 1,500 were fatal. The last major outbreak of the Zaire strain was in 2007, when 187 people died in Congo, a fatality rate of 74 percent.
Scientists are not clear how the virus – which also infects animals including bats, believed to be a major reservoir of the disease – crossed the continent from Sudan, Congo and Uganda. With ethnic and family ties and trade making cross-border travel common in the region, the outbreak in Guinea is causing concern in nearby West African nations.
In Ivory Coast, a neighbor of Guinea’s to the east, authorities said there were no suspected cases but they advised residents to avoid eating bushmeat – a carrier of the disease – and regularly wash their hands. Mali said it was working with the WHO to put in place preventive measures, including stronger border control health checks, and a mechanism for coping with potential victims.
Ebola virus disease (EVD) or Ebola hemorrhagic fever (EHF) is the human disease that may be caused by any of four of the five known ebola viruses. These four viruses are: Bundibugyo virus (BDBV), Ebola virus (EBOV), Sudan virus (SUDV), and Taï Forest virus (TAFV, formerly and more commonly Côte d’Ivoire Ebola virus (Ivory Coast Ebolavirus, CIEBOV)). EVD is a viral hemorrhagic fever (VHF), and is clinically nearly indistinguishable from Marburg virus disease (MVD).
The genera Ebolavirus and Marburgvirus were originally classified as the species of the now-obsolete Filovirus genus. In March 1998, the Vertebrate Virus Subcommittee proposed in the International Committee on Taxonomy of Viruses (ICTV) to change the Filovirus genus to the Filoviridae family with two specific genera: Ebola-like viruses and Marburg-like viruses. This proposal was implemented in Washington, DC on April 2001 and in Paris on July 2002. In 2000, another proposal was made in Washington, DC, to change the “-like viruses” to “-virus” resulting in today’s Ebolavirus and Marburgvirus.
Rates of genetic change are 100 times slower than influenza A in humans, but on the same magnitude as those of hepatitis B. Extrapolating backwards using these rates indicates that Ebolavirus and Marburgvirus diverged several thousand years ago.However, paleoviruses (genomic fossils) of filoviruses (Filoviridae) found in mammals indicate that the family itself is at least tens of millions of years old. Fossilized viruses that are closely related to ebolaviruses have been found in the genome of the Chinese hamster.
Signs and symptoms
Manifestation of Ebola begins with a sudden onset of an influenza-like stage characterized by general malaise, fever with chills, arthralgia, myalgia, and chest pain. Nausea is accompanied by abdominal pain, diarrhea, and vomiting. Respiratory tract involvement is characterized by pharyngitis with sore throat, cough, dyspnea, and hiccups. The central nervous system is affected as judged by the development of severe headaches, agitation, confusion, fatigue, depression, seizures, and sometimes coma.
Cutaneous presentation may include: maculopapular rash, petechiae, purpura, ecchymoses, and hematomas (especially around needle injection sites). In general, development of hemorrhagic symptoms is indicative of a negative prognosis. However, contrary to popular belief, hemorrhage does not lead to hypovolemia and is not the cause of death (total blood loss is low except during labor). Instead, death occurs due to multiple organ dysfunction syndrome due to fluid redistribution, hypotension, disseminated intravascular coagulation, and focal tissue necroses. The mean incubation period, best calculated currently for EVD outbreaks due to EBOV infection, is 12.7 days (standard deviation = 4.3 days), but can be as long as 25 days.
Haemorrhage
All patients show some extent of coagulopathy and impaired circulatory system symptomology. Bleeding from mucous membranes and puncture sites is reported in 40–50% of cases, while maculopapular rashes are evident in approximately 50% of cases. Sources of bleeds include hematemesis, hemoptysis, melena, and aforementioned bleeding from mucous membranes (gastroinestinal tract, nose, vagina and gingiva). Diffuse bleeding, however, is rare, and is usually exclusive to the gastrointestinal tract.
Risk factors
Between 1976 and 1998, from 30,000 mammals, birds, reptiles, amphibians, and arthropods sampled from outbreak regions, no ebolavirus was detected apart from some genetic traces found in six rodents and one shrew collected from the Central African Republic. Traces of EBOV were detected in the carcasses of gorillas and chimpanzees during outbreaks in 2001 and 2003, which later became the source of human infections. However, the high lethality from infection in these species makes them unlikely as a natural reservoir. Plants, arthropods, and birds have also been considered as possible reservoirs; however, bats are considered the most likely candidate. Bats were known to reside in the cotton factory in which the index cases for the 1976 and 1979 outbreaks were employed, and they have also been implicated in Marburg virus infections in 1975 and 1980. Of 24 plant species and 19 vertebrate species experimentally inoculated with EBOV, only bats became infected. The absence of clinical signs in these bats is characteristic of a reservoir species. In a 2002–2003 survey of 1,030 animals including 679 bats from Gabon and the Republic of the Congo, 13 fruit bats were found to contain EBOV RNA fragments. As of 2005, three types of fruit bats have been identified as being in contact with EBOV. They are now suspected to represent the EBOV reservoir hosts.
Bats drop partially eaten fruits and pulp, then terrestrial mammals such as gorillas and duikers feed on these fallen fruits. This chain of events forms a possible indirect means of transmission from the natural host to animal populations, which have led to research towards viral shedding in the saliva of bats. Fruit production, animal behavior, and other factors vary at different times and places that may trigger outbreaks among animal populations. Transmission between natural reservoirs and humans are rare, and outbreaks are usually traceable to a single index case where an individual has handled the carcass of gorilla, chimpanzee, or duiker. The virus then spreads person-to-person, especially within families, hospitals, and during some mortuary rituals where contact among individuals becomes more likely.
The virus has been confirmed to be transmitted through body fluids. Transmission through oral exposure and through conjunctiva exposure is likely and has been confirmed in non-human primates. Filoviruses are not naturally transmitted by aerosol. They are, however, highly infectious as breathable 0.8–1.2 micrometre droplets in laboratory conditions; because of this potential route of infection, these viruses have been classified as Category A biological weapons.
All epidemics of Ebola have occurred in sub-optimal hospital conditions, where practices of basic hygiene and sanitation are often either luxuries or unknown to caretakers and where disposable needles and autoclaves are unavailable or too expensive. In modern hospitals with disposable needles and knowledge of basic hygiene and barrier nursing techniques, Ebola has never spread on a large scale. In isolated settings such as a quarantined hospital or a remote village, most victims are infected shortly after the first case of infection is present. The quick onset of symptoms from the time the disease becomes contagious in an individual makes it easy to identify sick individuals and limits an individual’s ability to spread the disease by traveling. Because bodies of the deceased are still infectious, some doctors had to take measures to properly dispose of dead bodies in a safe manner despite local traditional burial rituals.
Prevention
As an outbreak of ebola progresses, bodily fluids from diarrhea, vomiting, and bleeding represent a hazard. Due to lack of proper equipment and hygienic practices, large-scale epidemics occur mostly in poor, isolated areas without modern hospitals or well-educated medical staff. Many areas where the infectious reservoir exists have just these characteristics. In such environments, all that can be done is to immediately cease all needle-sharing or use without adequate sterilization procedures, isolate patients, and observe strict barrier nursing procedures with the use of a medical-rated disposable face mask, gloves, goggles, and a gown at all times, strictly enforced for all medical personnel and visitors. The aim of all of these techniques is to avoid any person’s contact with the blood or secretions of any patient, including those who are deceased.
Vaccines have protected nonhuman primates. The six months needed for immunization impede counter-epidemic uses. In 2003, a vaccine using an adenoviral (ADV) vector carrying the Ebola spike protein therefore was tested on crab-eating macaques. The monkeys twenty-eight days later were challenged with the virus and remained resistant. A vaccine based on attenuated recombinant vesicular stomatitis virus (VSV) vector carrying either the Ebola glycoprotein or the Marburg glycoprotein in 2005 protected nonhuman primates, opening clinical trials in humans. The study by October completed the first human trial, over three months giving three vaccinations safely inducing an immune response. Individuals for a year were followed, and, in 2006, a study testing a faster-acting, single-shot vaccine began; this new study was completed in 2008. Trying the vaccine on a strain of Ebola that more resembles the one that infects humans is the next step.
Because of the virus’s high mortality, it is a potential agent for biological warfare. Given the lethal nature of Ebola, and since no approved vaccine or treatment is available, it is classified as a biosafety level 4 agent, as well as a Category A bioterrorism agent by the Centers for Disease Control and Prevention. It has the potential to be weaponised for use in biological warfare. The BBC reports in a study that frequent outbreaks of Ebola may have resulted in the deaths of 5,000 gorillas.
Authors: Alphonso Toweh and Saliou Samb
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