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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

characteristic of Gram negative bacteria
jane Reply
Characteristics of Gram Negative Bacteria As with Gram positive bacteria, Gram negative bacteria also contain the peptidoglycan polymer in their cell wall. While this polymer is thin (2 to 4 nanometers in thickness with just about 3 layers of peptidoglycan) in Gram negative bacteria, it's also com
Kaviya
it's also composed of long glycan strands that are cross-linked by peptide molecules. This composition serves a number of functions including protecting the bacterial cell from lysis
Kaviya
Good shot
Enoch
Thanks 😊
Kaviya
what was Hans Christian Gram's supported in the modern Microbiology?
Wilson Reply
what is microbial growth
Chisa Reply
The organism responsible for vulva ulcers
nyiter Reply
Why are vascular pathogen poorly communicable from person to person?
Aj Reply
Most vascular pathogens are poorly communicable from person to person because they need a medium to be communicated i,e a vector that would carry them from one person to other
Kaviya
what's the habit of protista
Afieahngwi Reply
They show both autotrophic and heterotrophic mechanisms...
Swetha
thanks
Afieahngwi
welcome...
Swetha
let me mention some water. Air .Food and so on
Gattiek Reply
causes of infectious diseases
Afieahngwi Reply
water.Air
Gattiek
infectious disease are caused by pathogenic micro organisms like bacteria ,fungi..
Swetha
What is pasteurization?
Wilson
are fungi prokaryote or eukaryotes?
Afieahngwi Reply
fungi are eukaryotes.
Swetha
All fungi are eukaryotes. Even micro fungi.
Lad
have..complex cellular organization and membrane bound nucleus ...and..also... having loops of DNA( like plasmids) as.bacteria
Swetha
what enzyme replaces rna nucleotides with dna nucleotides during replication?
Remi Reply
an enzyme called DNA ligase.
Jael
describe the acid fast staining procedure used in the diagnosis of tuberculosis
Salma Reply
bacterial morphology
lf_ Reply
what is the difference between biogenesis & abiogenesis
Mayuri Reply
biogenesis is when living comes out from other living things as a result of reproduction while a biogenesis is the process where living things comes out from non living things
Usman
living things come form other form living things is biogenesis. ....right?
Mayuri
what is mean by pasturation method?
Mayuri Reply
Pasteurization is a process that kills harmful bacteria and creates an extended shelf life for your milk. ... It's pretty simple—we take the milk from the cows, we rapidly heat it to a high enough temperature to kill the bacteria, and then we cool it back down before packaging and shipping it to you
Kaviya
tell me about abiogenessis &biogenesis
Mayuri
discribe aristol spontaneous generation theory in brif
Mayuri Reply
The Greek philosopher Aristotle (384–322 BC) was one of the earliest recorded scholars to articulate the theory of spontaneous generation, the notion that life can arise from nonliving matter. Aristotle proposed that life arose from nonliving material if the material contained pneuma (“vital heat”).
Kaviya
thank you 😊
Mayuri
No mention dear 😊
Kaviya

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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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