Download By: Monica Carbajal Etiology: Ebola is the virus that causes Ebola

Ebola
By: Monica Carbajal
Etiology: Ebola is the virus that causes Ebola hemorrhagic fever. It is a member of the
Filoviridae (filovirus) family. Its genus is Ebolavirus and it consists of five strains; Bundibugyo
ebolavirus, Zaire ebolavirus, Reston ebolavirus, Sudan ebolavirus, and Tai Forest ebolavirus
(formally Cote d’Ivoire ebolavirus). Four of the five strains cause disease in humans and Reston
virus only cause disease in animals. [1] [10]
Transmission: WHO [1]
Ebola is transmitted through direct contact between an infected animal to a human. Scientists
believe this is how Ebola emerged. Ebola is spread mainly through direct contact between the
blood, secretions and bodily fluids of an infected person to another person. Other modes of
transmission include exposure to objects (like needles) that have been contaminated with
infected secretions and direct contact with the cadaver of an infected human such as in burial
ceremonies. [1]
Reservoirs: The reservoir of Ebola is unknown but experts believe its zoonotic (animal borne)
and bats are likely the reservoir. This is based on current evidence and the nature of similar
viruses. Four of the five strains happen in animal hosts that are native to Africa. [10]
General Characteristics and Tests for Identification/Diagnosis:
Ebola is a member of the filovirus family which is helical, non-segmented, negative- stranded
RNA viruses. [7]
Before diagnosing Ebola, healthcare workers need to rule out other disease such as typhoid fever,
malaria, cholera, hepatitis, leptospirosis, etc… [9] There are several laboratory tests used to
confirm Ebola. These tests are considered extremely biohazard risk and should be done under
maximum biological contamination conditions. Deaths of healthcare workers during outbreaks
are due to lack of protective clothing or improper handling of specimens. [5] The laboratory tests
performed include an antigen-capture ELIZA test, an antigen detection test, a reverse
transcriptase polymerase chain reaction assay (RT-PCR) and virus isolation. [2] [9]
Signs and Symptoms:
Symptoms appear two to twenty-one days after exposure. Initial symptoms include diarrhea,
fever, headache, muscle pain and vomiting. Severe symptoms follow which consists of hiccups,
rash, difficulty breathing, chest pain and internal and external bleeding. [5] [6]
Historical Information:
Ebola appeared in 1976 in two outbreaks, one in Sudan and another in the Democratic Republic
of Congo where it appeared in a village near the Ebola River and acquired its name. The
mortality for the outbreak of Sudan (Sudan ebolavirus) was 53% and infected 284. The second
outbreak in the Rep. of Congo (Zaire ebolavirus) had a mortality rate of 88% and infected 318
people. In 1989 the Reston ebolavirus strain was identified in monkeys that were imported from
the Philippines into Reston, Virginia and Texas. The last strain, Tai Forest ebolavirus, was
discovered in the Tai Forest where an ethologist accidentally infected herself during a necropsy
on a dead chimpanzee. [1] [12] Sporadic outbreaks have occurred throughout the years in dense
forest areas in central Africa like Congo, Uganda and Democratic Republic of Congo. [11]
Virulence Factors:
Evidence shows that Ebola virus overthrows the innate and adaptive immune system responses
and triggers am inflammatory response so harmful that it causes direct tissue damage. The
immune system of the host is overwhelmed with the inflammatory response and cell damage
caused by the virus, especially the liver, and this leads to septic shock and death. [8]
Control/ Treatment:
Controlling the spread of Ebola is challenging since we know very little about the virus and
where it comes from. Lack of knowledge regarding the reservoir makes the public susceptible to
acquiring and spreading the virus unknowingly. Also, this virus spreads easily from direct
contact between people which make it harder to control. Ebola can also be misdiagnosed in the
early stages since early symptoms like fever and headache are common and nonspecific to Ebola.
[3]
There is no specific treatment. New drug therapies are being evaluated and some experimental
treatments have been effectively tested on animals but not in humans. [3] The only standard
treatment given to infected people is supportive therapy. This includes hydrating the patient,
treating them for any complicating infections, maintaining their oxygen level status and blood
pressure. [5]
Prevention/ Vaccine:
Prevention of Ebola is hard since it is unclear how people get infected. If a person is suspected of
carrying Ebola, they should be isolated and notify a healthcare professional. [3] Healthcare
workers and family who are in close contact with the patient, are at high risk of infection and
should use standard isolation precautions or barrier nursing techniques. These include wearing
personal protective equipment (goggles, masks, gowns and gloves) when in contact with patient,
complete equipment sterilization and routine use of disinfectant. [4] People who have died from
Ebola should be properly preserved and any direct contact with the body should be avoided. [1]
There is no vaccine available. Several vaccines are being tested but are not available. [9]
Local cases: The only cases of an Ebola outbreak in the U.S have happened in 1989,1990 and
1996. All the cases involved Reston virus, the only Ebolavirus strain that causes disease in
animals and not in humans. The disease was carried by monkeys from the Philippines to facilities
in Virginia and Texas without any deaths reported. [11]
Global Cases/Outbreaks:
On March 23, 2014 the World Health Organization was notified of an Ebola outbreak in Guinea.
A total of 49 cases, including 29 deaths (4 involving healthcare workers) with a mortality rate of
59%, had been reported as of March 22. The cases reported came from Guekedou, Macenta,
Nzerekore and Kissidougou districts in Guinea. There were also suspected cases in Liberia and
Sierra Leone at the time. [13] A virologic investigation confirmed Zaire ebolavirus as the
causative agent. [15] As of May 1st, 2014, there is a cumulative total of 226 clinical cases,
including 149 deaths in Guinea with the mortality rate at 90%. Two hundred and ten patients
were tested for Ebola and 127 cases have been confirmed by PCR, including 81 deaths. There is
also 44 cases are “probably cause for EVD”, 55 cases are “suspected cases” and 25 health care
workers were infected, including 16 deaths. There is still seven patients in isolation in Guinea. In
Liberia, as of May 2nd the total number of cases was 13 (6 confirmed, 2 probably and 5
suspected), including 11 deaths. There have not been ant new cases in this area as of the 6th of
April. [14] The end to this outbreak has not been declared yet and it is expected that the numbers
may continue to rise as everyone battles to control the outbreak.
References:
[1] "Ebola virus disease: background and summary." WHO. World Health Organization, 3 Apr.
2014. Web. 1 May 2014. <http://www.who.int/csr/don/2014_04_ebola/en/>.
[2] "Ebola Hemorrhagic Fever: Diagnosis ." Centers for Disease Control and Prevention. Centers
for Disease Control and Prevention, 28 Jan. 2014. Web. 1 May 2014.
<http://www.cdc.gov/vhf/ebola/diagnosis/index.html>.
[3] "Ebola Hemorrhagic Fever: Treatment." Centers for Disease Control and Prevention. Centers
for Disease Control and Prevention, 28 Jan. 2014. Web. 1 May 2014.
<http://www.cdc.gov/vhf/ebola/treatment/index.html>.
[4] "Ebola Hemorrhagic Fever: Prevention." Centers for Disease Control and Prevention. Centers
for Disease Control and Prevention, 10 Apr. 2014. Web. 1 May 2014.
<http://www.cdc.gov/vhf/ebola/prevention/index.html>.
[5] "Ebola." . Doctors Without Borders/Médecins Sans Frontières, n.d. Web. 1 May 2014.
<http://www.doctorswithoutborders.org/our-work/medical-issues/ebola>.
[6] Vyas, Jatin. "Ebola hemorrhagic fever: MedlinePlus Medical Encyclopedia." U.S National
Library of Medicine. U.S. National Library of Medicine, 1 Sept. 2013. Web. 1 May 2014.
<http://www.nlm.nih.gov/medlineplus/ency/article/001339.htm>.
[7] Waterman, Tara. "Ebola Classification and Taxonomy." Ebola Classification and Taxonomy.
N.p., 1 Jan. 1999. Web. 1 May 2014. <http://virus.stanford.edu/filo/class.html>.
[8] Zampieri, Carisa. "." Nature.com. Nature Publishing Group, 19 Oct. 2007. Web. 1 May 2014.
<http://www.nature.com/ni/journal/v8/n11/abs/ni1519.html>.
[9] "Ebola virus disease." WHO. World Health Organization, 1 Apr. 2014. Web. 1 May 2014.
<http://www.who.int/mediacentre/factsheets/fs103/en/>.
[10] "Ebola Hemorrhagic Fever." Centers for Disease Control and Prevention. Centers for
Disease Control and Prevention, 14 Apr. 2014. Web. 3 May 2014.
<http://www.cdc.gov/vhf/ebola/>.
[11] "Chronology of Ebola Hemorrhagic Fever Outbreaks ." Centers for Disease Control and
Prevention. Centers for Disease Control and Prevention, 30 Apr. 2014. Web. 3 May 2014.
<http://www.cdc.gov/vhf/ebola/resources/outbreak-table.html>.
[12] Waterman, Tara. "Brief General History of Ebola." Brief Ebola General History. N.p., 1 Jan.
1999. Web. 1 May 2014. <http://virus.stanford.edu/filo/history.html>.
[13] "Ebola Virus Disease in Guinea." . World Health Organization; Regional Office for Africa,
23 Mar. 2014. Web. 4 May 2014. <http://www.afro.who.int/en/clusters-a-
programmes/dpc/epidemic-a-pandemic-alert-and-response/outbreak-news/4063-ebolahemorrhagic-fever-in-guinea.html>.
[14] "Ebola virus disease, West Africa (Situation as of 2 May 2014)." . World Health
Organization: Regional Office for Africa, 2 May 2014. Web. 4 May 2014.
<http://www.afro.who.int/en/clusters-a-programmes/dpc/epidemic-a-pandemic-alert-andresponse/outbreak-news/4130-ebola-virus-disease-west-africa-2-may-2014.html>.
[15] Baize, Sylvain. "Emergence of Zaire Ebola Virus Disease in Guinea - Preliminary Report —
NEJM." New England Journal of Medicine. The New England Journal of Medicine, 16 Apr.
2014. Web. 4 May 2014.
<http://www.nejm.org/doi/full/10.1056/NEJMoa1404505?query=featured_home&&&>.