Ebola pathophysiology: Difference between revisions
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===Genome=== | ===Genome=== | ||
Each virion contains one minor molecule of linear, single-stranded, [[Sense (molecular biology)|negative-sense]] RNA, totaling 18959 to 18961 nucleotides in length. The 3′ terminus is not polyadenylated and the 5′ end is not capped. It was found that 472 nucleotides from the 3' end and 731 nucleotides from the 5' end were sufficient for replication.<ref name="Klenk2004" /> It codes for seven structural proteins and one non-structural protein. The gene order is 3′ - leader - NP - VP35 - VP40 - GP/sGP - VP30 - VP24 - L - trailer - 5′; with the leader and trailer being non-transcribed regions which carry important signals to control transcription, replication and packaging of the viral genomes into new virions. The genomic material by itself is not infectious, because viral proteins, among them the RNA-dependent RNA polymerase, are necessary to transcribe the viral genome into mRNAs, as well as for replication of the viral genome. | Each virion contains one minor molecule of linear, single-stranded, [[Sense (molecular biology)|negative-sense]] RNA, totaling 18959 to 18961 nucleotides in length. The 3′ terminus is not polyadenylated and the 5′ end is not capped. It was found that 472 nucleotides from the 3' end and 731 nucleotides from the 5' end were sufficient for replication.<ref name="Klenk2004" /> It codes for seven structural proteins and one non-structural protein. The gene order is 3′ - leader - NP - VP35 - VP40 - GP/sGP - VP30 - VP24 - L - trailer - 5′; with the leader and trailer being non-transcribed regions which carry important signals to control transcription, replication and packaging of the viral genomes into new virions. The genomic material by itself is not infectious, because viral proteins, among them the RNA-dependent RNA polymerase, are necessary to transcribe the viral genome into mRNAs, as well as for replication of the viral genome. | ||
==Transmission== | |||
===Transmission=== | |||
Among humans, the virus is transmitted by direct contact with infected [[body fluid]]s, or to a lesser extent, skin or [[mucous membrane]] contact. The [[incubation period]] can be anywhere from 2 to 21 days, but is generally between 5 and 10 days. | |||
Although [[airborne transmission]] between monkeys has been demonstrated by an accidental outbreak in a laboratory located in Virginia, USA, there is very limited evidence for human-to-human airborne transmission in any reported epidemics. [[Mayinga N'Seka|Nurse Mayinga]] might represent the only possible case. The means by which she contracted the virus remains uncertain. | |||
The infection of human cases with Ebola virus has been documented through the handling of infected chimpanzees, gorillas, and forest antelopes--both dead and alive--as was documented in Côte d'Ivoire, the Republic of Congo and Gabon. The transmission of the Ebola Reston strain through the handling of cynomolgus monkeys has also been reported. | |||
So far, 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 [[autoclave]]s are unavailable or too expensive. In modern hospitals with disposable needles and knowledge of basic hygiene and [[Universal precautions|barrier nursing]] techniques, Ebola has never spread on such a large scale. | |||
In the early stages, Ebola may not be highly contagious. Contact with someone in early stages may not even transmit the disease. As the illness progresses, bodily fluids from diarrhea, vomiting, and bleeding represent an extreme [[biohazard]]. 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 (microbiology)|sterilization]] procedures, to isolate patients, and to observe strict [[Universal precautions|barrier nursing]] procedures with the use of a medical rated disposable face mask, gloves, goggles, and a gown at all times. This should be strictly enforced for all medical personnel and visitors. | |||
Ebola is unlikely to develop(sometimes) into a [[Pandemic|pandemic]], or world-wide infection, due to its difficulty in spreading by [[airborne transmission]] and the period of time that the virus can use a living and contagious victim to spread compared to other infectious diseases. 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. In addition, 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, many doctors implemented measures to properly dispose of dead bodies in spite of some traditional local burial rituals.<ref name="nyt">{{cite news |first=Blaine |last=Harden |authorlink= |coauthors= |title=Dr. Matthew's Passion |url=http://www.nytimes.com/library/magazine/home/20010218mag%2debola.html |work=[[New York Times]] Magazine |publisher= |date=2001-02-18 |accessdate=2008-02-25 }}</ref> | |||
==References== | ==References== | ||
{{Reflist|2}} | {{Reflist|2}} | ||
Revision as of 15:07, 5 April 2012
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Ebola Microchapters |
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Diagnosis |
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Treatment |
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Postmortem Care |
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Case Studies |
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Ebola pathophysiology On the Web |
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American Roentgen Ray Society Images of Ebola pathophysiology |
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
Overview
Structure
Size and shape
Electron micrographs of members of Ebola virus show them to have the characteristic thread-like structure of a filovirus.[1] EBOV VP30 is around 288 amino acids long.[1] The virions are tubular and variable in shape and may appear as a "U", "6", coiled, circular, or branched shape, however, laboratory purification techniques, such as centrifugation, may contribute to the various shapes.[1] Virions are generally 80 nm in diameter.[1] They are variable in length, and can be up to 1400 nm long. On average, however, the length of a typical Ebola virus is closer to 1000 nm. In the center of the virion is a structure called nucleocapsid, which is formed by the helically wound viral genomic RNA complexed with the proteins NP, VP35, VP30 and L. It has a diameter of 40 – 50 nm and contains a central channel of 20–30 nm in diameter. Virally encoded glycoprotein (GP) spikes 10 nm long and 10 nm apart are present on the outer viral envelope of the virion, which is derived from the host cell membrane. Between envelope and nucleocapsid, in the so-called matrix space, the viral proteins VP40 and VP24 are located.
Genome
Each virion contains one minor molecule of linear, single-stranded, negative-sense RNA, totaling 18959 to 18961 nucleotides in length. The 3′ terminus is not polyadenylated and the 5′ end is not capped. It was found that 472 nucleotides from the 3' end and 731 nucleotides from the 5' end were sufficient for replication.[1] It codes for seven structural proteins and one non-structural protein. The gene order is 3′ - leader - NP - VP35 - VP40 - GP/sGP - VP30 - VP24 - L - trailer - 5′; with the leader and trailer being non-transcribed regions which carry important signals to control transcription, replication and packaging of the viral genomes into new virions. The genomic material by itself is not infectious, because viral proteins, among them the RNA-dependent RNA polymerase, are necessary to transcribe the viral genome into mRNAs, as well as for replication of the viral genome.
Transmission
Transmission
Among humans, the virus is transmitted by direct contact with infected body fluids, or to a lesser extent, skin or mucous membrane contact. The incubation period can be anywhere from 2 to 21 days, but is generally between 5 and 10 days.
Although airborne transmission between monkeys has been demonstrated by an accidental outbreak in a laboratory located in Virginia, USA, there is very limited evidence for human-to-human airborne transmission in any reported epidemics. Nurse Mayinga might represent the only possible case. The means by which she contracted the virus remains uncertain.
The infection of human cases with Ebola virus has been documented through the handling of infected chimpanzees, gorillas, and forest antelopes--both dead and alive--as was documented in Côte d'Ivoire, the Republic of Congo and Gabon. The transmission of the Ebola Reston strain through the handling of cynomolgus monkeys has also been reported.
So far, 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 such a large scale.
In the early stages, Ebola may not be highly contagious. Contact with someone in early stages may not even transmit the disease. As the illness progresses, bodily fluids from diarrhea, vomiting, and bleeding represent an extreme biohazard. 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, to isolate patients, and to observe strict barrier nursing procedures with the use of a medical rated disposable face mask, gloves, goggles, and a gown at all times. This should be strictly enforced for all medical personnel and visitors.
Ebola is unlikely to develop(sometimes) into a pandemic, or world-wide infection, due to its difficulty in spreading by airborne transmission and the period of time that the virus can use a living and contagious victim to spread compared to other infectious diseases. 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. In addition, 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, many doctors implemented measures to properly dispose of dead bodies in spite of some traditional local burial rituals.[2]
References
- ↑ 1.0 1.1 1.2 1.3 1.4 Klenk, Hans-Dieter (2004). Ebola and Marburg Viruses, Molecular and Cellular Biology. Wymondham, Norfolk: Horizon Bioscience. ISBN 0954523237. Unknown parameter
|coauthors=ignored (help) - ↑ Harden, Blaine (2001-02-18). "Dr. Matthew's Passion". New York Times Magazine. Retrieved 2008-02-25.