Everyone Has Herpes Viruses
Posted by admin in Microbiology on June 18, 2011
Overview of the Nine Types of Herpes Viruses Found in Humans
1. Herpes simplex virus Type 1 (HSV-1)
Fever blisters and cold sores of the face, mouth, and lips are the most common symptoms of HSV-1 outbreaks. Also known as Human Herpes Virus-1 (HHV-1).
Surprisingly, most infections with this virus occur by two years of age via breaks in the skin barrier around the mouth or elsewhere on the body. While HSV-1 is thought of as the cold sore virus and HSV-2 (see below) is thought of as the genital herpes virus, distinctions between them often fail. It is well documented in the medical literature, although not yet widely publicized, that the virus released from a cold sore can easily transfer via oral-genital contact to establish a genital herpes infection in another individual.
Besides causing cold sores and possibly spreading to the genital region, HSV-1 has also been linked with the development of serious neurological diseases such as Alzheimer’s disease, Bell’s palsy and trigeminal neuralgia. Recent research also shows that co-infection by HSV-1 and HIV (human immunodeficiency virus) can enhance the activity of both viruses in patients who have AIDS and non-genital herpes lesions.
HSV-1 infects at least 50% of people worldwide.
2. Herpes simplex virus Type 2 (HSV-2)
Also called Human Herpes Virus-2 (HHV-2). This type is the usual cause of genital herpes, which is classified as a sexually transmitted disease. HSV-2 reached epidemic status in the 1980s and 1990s, mostly because of its increased incidence among teenagers. In the world of virus classification, HSV-2 and HSV-1 are nearly indistinguishable except for their different clinical symptoms. However, even these differences are inconsistent, since both types of herpes simplex can cause oral and genital herpes outbreaks.
3. Herpes zoster virus (HZV)
Also called Varicella zoster virus (VZV) and Human Herpes Virus-3 (HHV-3). Chickenpox results from a first time infection by HZV. When this virus recurs later in a person’s life, it causes shingles. As the average age of our population increases, more and more people are suffering recurring bouts of post herpetic neuralgia (nerve pain) as a result of shingles. This herpes virus is considered to be the most infectious of the known herpes viruses. Greater than 90% of the population is infected.
HZV has been linked to the autoimmune disease called lupus. Furthermore, HZV outbreaks, which are now epidemic among people with AIDS, are often the earliest indicator of HIV infection. Read the rest of this entry »
Virus Classification
Posted by admin in Microbiology on June 18, 2011
Virus classification is the process of naming viruses and placing them in a ‘family tree’ in relation to other viruses. This process is different from the one used to classify plants or animals. Thanks to the fossil record, there are clear connections between most animals or plants. Viruses do not leave such a record, so it is more difficult to determine relationships between them. Another factor causing difficulties in virus classification is their pseudo-living nature, many scientists are debating whether viruses should be considered alive because they are missing several criteria considered important for living creatures. This makes viruses very difficult to place in the current classification system for plants and animals.
Virus classification is currently based on five phenotypic characteristics; morphology, or structure, of the virus; type of nucleic acid, or the genetic material, of the virus; mode of replication; hosts; and the type of disease they cause. There are two classification systems in use today, the Baltimore system and the International Committee on the Taxonomy of Viruses classification guidelines.
The Baltimore classification system was developed by Nobel Prize winning biologist, David Baltimore. This system separates viruses into seven groups, designated by Roman numerals, depending on their type of genetic material, the number of strands of genetic material and their method of replication. There are other classification systems that are based on the morphology of the virus or the disease caused. These systems are inadequate due to the fact that some diseases are caused by different viruses, the cold or flu are the most common example of this and some viruses look very similar to one another. Another factor is viral structures are difficult to determine under a microscope thanks to their small size. By classifying viruses based on their genetic material, some indication of how to proceed with research is provided because viruses in a category behave in a similar manner.
The seven groups are: Group I, double stranded DNA viruses such as the herpes virus and the chickenpox virus; Group II, single stranded DNA viruses such as the parvo virus; Group III, double stranded RNA viruses; Group IV, positive-sense single stranded RNA viruses such as the Sars virus, the yellow fever virus and many other well known viruses; Group V, negative-sense single stranded RNA viruses such as the measles virus, the mumps virus and the rabies virus; Group VI, reverse transcribing RNA viruses such as HIV; and Group VII, reverse transcribing DNA viruses such as the hepatitis B virus. The Group VI viruses use the enzyme to reverse-transcribe their RNA into DNA and then insert the transcribed DNA into the host organism’s DNA, where it is replicated whenever a cell divides. The Group VII viruses transcribe their DNA into an RNA form, then transcribe the RNA back into DNA to be inserted into the host’s DNA and replicated. Read the rest of this entry »