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Figure a is an electron micrograph that shows a a shpere within a larger blob-shaped structure. Figure b shows raised red dots on a person’s back.
(a) Varicella-zoster, the virus that causes chickenpox, has an enveloped icosahedral capsid visible in this transmission electron micrograph. Its double-stranded DNA genome becomes incorporated in the host DNA. (b) After a period of latency, the virus can reactivate in the form of shingles, usually manifesting as a painful, localized rash on one side of the body. (credit a: modification of work by Erskine Palmer and B.G. Partin—scale-bar data from Matt Russell; credit b: modification of work by Rosmarie Voegtli)

Latent viruses may remain dormant by existing as circular viral genome molecules outside of the host chromosome. Others become proviruses by integrating into the host genome. During dormancy, viruses do not cause any symptoms of disease and may be difficult to detect. A patient may be unaware that he or she is carrying the virus unless a viral diagnostic test has been performed.

Chronic infection

A chronic infection is a disease with symptoms that are recurrent or persistent over a long time. Some viral infections can be chronic if the body is unable to eliminate the virus. HIV is an example of a virus that produces a chronic infection, often after a long period of latency. Once a person becomes infected with HIV, the virus can be detected in tissues continuously thereafter, but untreated patients often experience no symptoms for years. However, the virus maintains chronic persistence through several mechanisms that interfere with immune function, including preventing expression of viral antigens on the surface of infected cells, altering immune cells themselves, restricting expression of viral genes, and rapidly changing viral antigens through mutation. Eventually, the damage to the immune system results in progression of the disease leading to acquired immunodeficiency syndrome (AIDS). The various mechanisms that HIV uses to avoid being cleared by the immune system are also used by other chronically infecting viruses, including the hepatitis C virus.

  • In what two ways can a virus manage to maintain a persistent infection?

Life cycle of viruses with plant hosts

Plant viruses are more similar to animal viruses than they are to bacteriophages. Plant viruses may be enveloped or non-enveloped. Like many animal viruses, plant viruses can have either a DNA or RNA genome and be single stranded or double stranded. However, most plant viruses do not have a DNA genome; the majority have a +ssRNA genome, which acts like messenger RNA (mRNA). Only a minority of plant viruses have other types of genomes.

Plant viruses may have a narrow or broad host range. For example, the citrus tristeza virus infects only a few plants of the Citrus genus, whereas the cucumber mosaic virus infects thousands of plants of various plant families. Most plant viruses are transmitted by contact between plants, or by fungi, nematodes, insects, or other arthropods that act as mechanical vectors. However, some viruses can only be transferred by a specific type of insect vector; for example, a particular virus might be transmitted by aphids but not whiteflies. In some cases, viruses may also enter healthy plants through wounds, as might occur due to pruning or weather damage.

Questions & Answers

define polar bond in simple way
Rashmi Reply
Hi everyone, is these site only about microbiology? I want a site which I can download articles on hematological and biochemical profile
Peter Reply
I think it is only about micro biology.
Kimberly
so whats happening
Michael
I am about to enter school and am going for MCB
Olugbenga Reply
What is DNA damage and repair
Sree Reply
removal of nucleotide bases from DNA is damage n addition or insertion of bases in DNA is repair.
Rashmi
replication is a term related to generation of new DNA from a parental DNA.
Rashmi
role of microorganism as pathogens
Parteek Reply
to live inside the host body, reproduction n destroy the immune system of host body.
Rashmi
what is replication
rajesh
please give me ans
rajesh
replication is a term related to generation of new DNA from parental DNA.
Rashmi
difference between endotoxin and exotoxin
Binkheir Reply
toxins released inside the cell or a body is endotoxin n toxins released outside the cell or a body is exotoxin.
Rashmi
please I want the names of bacteria and the diseases they cause.
Ibrahim Reply
there are many we classify it according to their shapes gram negative or gram positive
Tharra
so u may refer the book u guess or by when u want I can do a list for you and send u here
Tharra
😊
Tharra
please do a list for me
Ibrahim
I have the lost but it's too much to type ..
Tharra
MSc entrance prepare books and questions LA etha base pani irukum..
Guhan Reply
kushal always prescott is the imp book to follow.search some objective mcqs books based on your syllabus
deepthi Reply
I want to clear entrance of ms university so I have no more idea so my preparation is based on my bachlor studies.
Kushal
what are the opportunistic infection in aids stage
Kalkak
certain cancer or pneumonia 🤔
Kushal
penicillium crysogenum
Kushal Reply
salam am also studying microbiology in university of Ilorin
Abubakar Reply
Salam am studying physiotherapy in bayaro university kano
Tasiu
Walaikum salam
Hakeeb
Hw u
Tasiu
HRU frinds
Arhaan
any good reference for oncology?!!!!
Pankaj Reply
K.D tripathi
Vinod
what is the microbiology
Fadumo Reply
it is the study of microorganisms
Sneha
microorganis means
Ghuge
the organism can not be seen by eyes they can be seen with the help of microscope
rajesh
microbiology is the study of microorganism and microorganism are such as bacteria ,parasite, viruses and fungi and etc.. those are cant be seen with asked eyes and can be seen with help of microscope . I hope this helps you
Tharra
what is virology
Bismarck Reply
the study of viruses
Adan
what is myrology
Bismarck
myrology or mycology?
Adan
mycology
Bismarck
the study of fungi.
Adan
Mycology study fungi
Hakeeb
study of viruses
Rashmi
what are the major topics that you cover under micro biology
Bismarck Reply
virology,mycology,bacteriology
Adan
identification n application of microorganisms
Rashmi

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Source:  OpenStax, Microbiology. OpenStax CNX. Nov 01, 2016 Download for free at http://cnx.org/content/col12087/1.4
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