Uses of Viruses

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Viruses cause us much harm, however, their infectiouos ability have made them the prime candidate as vectors in gene therapy. Removing the harmful codes in their genome and using them to infect the target host cell and integrate the desired gene into the host genome is the idea.

They do run the risk of infecting the host despite removing the known disease causing part of the viral      genome. Click here to learn more about them.

Another use for viruses would be when they are dead and used as vaccines. This method has been in use for some time now. Click here to more about them.

(Image: www.accessexcellence.org/.../making_vaccines.php)



Apart from being used in the medical sector, viruses have also been introduced as biological pest controls. Read on to learn how they help to control insects which harm crops.

Video of Virus Entry

Video

This video shows the general viewer a simple overview of how a virus infects a host cell and replicates.

Virus Control

The virus is not controlled by antibodies that come in tablets. We can control viral infections of the body only with our immune system. Our white blood cells would combat with these foreign bodies when they are exposed to them. This concept is the basis of vaccines where dead viruses are injected into the body for the immune system to build up defence to it. Eventually, when the virus does infect the patient, he is able to counter the attack.

Viruses mutate at high rate, which impedes the body's immune system to control it. Different strains of a virus are increasingly found today. The flu virus itself has shown many faces, like H1N1 and H5N1.

Scientists have made breakthroughs in controlling virus growth. As mentioned about viruses having viral enzymes to fascilitate their replication and assembly, using enzyme inhibition could stop the virus. Since each step in the life cycle of a virus involves an enzyme, creating drugs that inhibit the enzyme prevents the growth of the virus. The challenges lie in early detection of the infection and the mutation rate of the virus. Using this concept, drugs have been made for the HIV.



Groups of Antiretroviral Drugs


There are five groups of antiretroviral drugs. Each of these groups attacks HIV in a different way.



1. Nucleoside/Nucleotide Reverse Transcriptase Inhibitors NRTIs  --  NRTIs interfere with the action of an HIV protein called reverse transcriptase, which the virus needs to make new copies of itself.

2. Non-Nucleoside Reverse Transcriptase Inhibitors NNRTIs --  NNRTIs also stop HIV from replicating within cells by inhibiting the reverse transcriptase protein.

3. Protease Inhibitors PIs --  which is another protein involved in the HIV replication process.

4. Fusion or Entry Inhibitors --  prevent HIV from binding to or entering human immune cells.

5. Integrase Inhibitors -- interfere with the integrase enzyme, which HIV needs to insert its genetic material into human cells.

(Drugs information from: http://www.avert.org/treatment.htm)

Viruses

Viruses are very small parasites. They infect host cells and cause diseases. However, the detection of viral infection could be difficult as they could remain dormant for long periods before any symptoms are visible. Viruses are acellular, they do not respire outside host cells.

(Image of virus: www.armageddononline.org/.../viruses.html )

Properties

Viral Genome :  DNA or RNA contained in Protein coat or Capsid

Shape            :  Various shapes

Size               :  10 - 100 nm

May or may not have lipid bilayer envelope and contains viral enzymes. These carry out viral replication and assemply.

( Image of various virus shapes: cesarharada.com/pearls/category/structure/ )

Influenza Symptoms

Influenza is an acute virus disease that is characterized by acute toxicosis, moderate catarrhal signs with most intensive affection of trachea and bronchi.

The clinical picture of influenza and acute respiratory diseases caused by different kinds of viruses, for compatibility of common toxic symptoms, has many common features.

Usually influenza starts acutely. Incubation period as a rule lasts 1- 2 days but it can last 5 days.

Then starts period of acute clinical manifestation. Disease severity depends on many factors: general condition, age, also it is necessary to know if patient contacted with this type of virus before. Depending on all those factors patient can have one of four types of influenza: mild, moderately severe, severe, hypertoxic. Symptoms and their intensity depend on disease severity.

In case of mild influenza forms (including subclinical forms) body temperature can remain normal or it can rise up to 38C. Symptoms of infective toxicosis are mild or are missing.

In case of moderately severe influenza form, body temperature rises up to 38,5-39,5°С and are common the next symptoms:
1) Intoxication

• abundant sweating
• lack of energy
• photophobia
• joint and muscle pain
• headache

2) Catarrhal symptoms

• hyperemia of velum and back of the throat
• conjunctiva hyperemia

3) Respiratory symptoms

• affection of throat and trachea
• dry painful cough (in some cases wet cough)
• phonation defect
• chest pains
• rhinitis (cold)
• hyperemia
• dryness of nasal lining and swallow

Lungs skip lesion syndrome is a dynamically growing (for several hours) pulmonary heart disease with typical segmental shade in one of lungs. In case of favorable result clinicoroentgenological changes are solved in 2-3 days practically entirely – this is the major difference from pneumonia. In case of hypertoxic form of influenza is possible to have wet lungs usually ending with hemorrhagic pneumonia.

Abdominal syndrome:

• abdominal pains
• diarrhea occurs rarely and as a rule it is a sign of other infections. What is known as “Norovirus” is caused not by influenza virus.

Severe form of influenza

Body temperature rises up to 40-40,5°С. In addition to the symptoms specific for moderately severe influenza form also may appear signs of encephalopathy (psychosis state, convulsive attack, hallucination), vascular disorders (nose bleed), vomit.

Hypertoxic form of influenza.

There is a serious danger of fatal case especially for diseased from risk group.

When influenza courses without any complications, fever lasts 2-4 days and finally patient is recovered in 5 days. It is possible to have occasional temperature rises which are usually associated with bacterial flora lay-up or another virus respiratory infection.

Influenza

Influenza (flu) is a severe virus disease which affects men, women and children of all ages and nationalities. The disease is followed by high mortality, especially among little kids and old people. The epidemics of flu occur every year usually in cold season and it hit up to 15% of population in the world.

Periodically repeating, flu and ARD destroy about one year of our life. A man spends this period in inactive condition suffering from fever, common weakness, headaches, intoxication with toxic virus proteins.

Flu gradually breaks heart-vascular system shortening lifetime of an average man. During severe course of this virus disease often occurs irreversible affection of heart-vascular system, respiratory organ, central nervous system provoking heart and vascular diseases, pneumonia, tracheobronchitis, meningoencephalitis.

Term “Acute Respiratory Disease” (ARD) or “Acute Respiratory Viral Infection” (ARVI) comprises a vast number of similar diseases. They are similar because they are caused by viruses invading organism by respiring air via mouth and nasal pharynx, and also they have similar symptoms: increased temperature of the body, sore throat, cough and headache. The most common respiratory disease is acute rhinitis (cold) that is caused by a number of congenerous viruses called rhinoviruses. During recovery all those symptoms disappear and they do not leave any signs. However, it would be wrong to call “flu” all kinds of ARD and ARVI. Flu is caused by a flu virus (Myxovirus influenzae) that belongs to the family of orthomyxoviruses.

Flu and ARVI are leading in frequency and number of cases and are 95% of all virus diseases.

About the origin of word “influenza” there are several versions. According to one of them, the word has appeared in Italy in the mid of 15th century after a serous epidemic which people thought to be the result of stars influence. Another version says that the word is originated from Latin word “influere” (invade) or Italian "influenza di freddo" (cooling after-effect).