Ebola virus is difficult to study due to the high risk for the researcher, but plausible ideas about how the virus functions have been developed. The structure of this filovirus is large and unique. Ebola virus forms variable length filamentous capsids that are sometimes branched. ?Figure 19-28? shows an electron micrograph of Ebola virus. Only Ebola viruses of a certain size are infective and the viruses variable length and large size is very unusual. It is possible that the very large variants are due to errors in assembly. Capsid: The capsid has a helical morphology and is encased inside a membrane envelope.
Several viral proteins and glycoproteins stud the membrane. The primary capsid protein is a nucleoprotein (NP) whose N terminal interacts with viral RNA and the rest contacts other viral proteins in the matrix or envelope. Genome: The nucleic acid of the virus consists of a single-stranded (-) RNA molecule, reminiscent of influenza virus. The genome codes for seven genes and seven separate transcriptional units are made into mRNA upon infection. Caps and polyadenylated tails are added during creation of the mRNA. The genome of Ebola is shown in the next slide. ?
Image:0The genome of Ebola virus. The (-) ssRNA genome of Ebola virus is arranged in 7 separate units. The location of the coding region for each protein in shown in lower panel. Replication: The mechanisms of attachment and entry of the virus are not clear, but are assumed to be similar to those of other (-) strand RNA viruses, such as influenza virus. Replication is thought to occur in the cytoplasm. An unusual feature of the transcription and translation of the Ebola genes is the fact that the GP protein is only expressed through ? transcriptional editing?.
In this process, the polymerase actually changes the growing mRNA, adding an extra A in the transcript to get the correct protein coding sequence for the GP protein. The replicative cycle of the virus is unknown, but likely involves a mechanism where the membrane proteins are produced at the ER, processed through typical cellular pathways, and sent to the membrane. The viral polymerase makes further mRNA transcripts and eventually begins replication of the virus, first making (+) RNA strands and then (-) RNA. Eventually, enough viral proteins and (-) RNA accumulate to allow viral assembly and then budding of the virus through the membrane.
Lytic: 0 Ebola typically bursts from the cells via apoptosis. Lytic viruses typically use the cell’s machinery to make as many virions as possible and burst the cell open in order to spread to more host cells. Transmittance: Spillover event: when patients come in contact with infected animals Fun Facts: ?Ebola is caused by an RNA virus. This emerging health threat is the result of a RNA (ribonucleic acid) virus that infects wild animals — like fruit bats, monkeys, gorillas, and chimpanzees — as well as people.
Contact with an infected animal’s blood or body fluids is probably the ? original source of the infectious disease?. Outbreaks of Ebola began in 1976 in the Democratic Republic of Congo on the Ebola River, and Sudan, with later outbreaks in Uganda and other African nations, according to ?
World Health Organization data?. ?Early ? Ebola symptoms? include fever, headache, body aches, cough, stomach pain, vomiting, and diarrhea. Because these could be symptoms of other diseases, it’s difficult to diagnose Ebola early on. The time it takes from exposure to Ebola to actually getting sick, known as the incubation period, is anywhere from 2 to 21 days, says UAB’s Pigott.
Most people who are infected with Ebola will develop early symptoms eight to nine days after exposure to the virus, according to the CDC?. Specific tests for antibodies against Ebola and viral DNA help doctors make a conclusive diagnosis. ?Later symptoms of Ebola can appear quickly, within a few days after onset of early symptoms. Due to internal and external bleeding, the patient’s eyes may become red, and they may vomit blood, have bloody diarrhea, and suffer cardiovascular collapse and death, explains Pigott. The only treatment doctors can provide is supportive care — they give the patient fluids and oxygen, and keep their blood pressure steady.