Viruses: A Peep into Understanding the Basic Details of Viruses


Want to know what are viruses? What do viruses contain and the characteristic features of viruses? Then read this article to understand about the viruses and the diseases they cause in man, animals and plants. What precautions to be taken to prevent virus diseases.

Introduction to Viruses

Viruses are group of microscopic organisms that can be seen only through electron microscope. Millions of viruses thrive in our environment, they are found in every ecosystem of the earth. They infect all kinds of life forms, plants, animals and human beings. Virus that attack plants are called plant viruses, Viruses that attack animals and human beings are called animal viruses. Viruses that attack bacteria are called bacterial virus or bacteriophage. Viruses spread in different ways. In plants they spread through insects and other organisms called as vectors. In human beings viruses spread through infected wounds, by droplets of air moisture, contamination of food and water through hands and by direct contact. The branch of biology that deals with the study of viruses is called as virology. Scientists who study about viruses are called virologists. They study about the microscopic viruses, their evolution, classification, their structure, reproduction, how they infect the host cells etc. Viruses are named based on their genetic structure and are so named by the International committee on Taxonomy of Viruses (ICTV). The most deadly viruses are Marbug virus, Ebola virus, Rabies virus, HIV, Hantavirus, Dengue Virus, Rota virus and the recent one SARS-CoV-2 called the COVID- 19 that is giving nightmares to people across the world.

Viruses Shapes and sizes

A virus particle is also called a virion. The shapes and sizes of viruses range from simple to helical and more complex, they occur in shapes of spherical, rod like, rounded, or in geometrical shapes. Viruses are measured in units called millimicrons and most viruses range from 2.5 to 250 millimicrons in size. The biggest known virus is the Mega virus with 440 nanometers in size and the smallest viruses being the Porcine Circovirus which has a size of about 17 nanometers. Viruses are smaller than bacteria.
Viruses are extremely small particles that are made up of two basic substances, the nucleic acids and the proteins. The nucleic acids contain DNA (deoxyribonucleic acid) or RNA (ribonucleic acid). Viruses do not have both DNA and RNA. The nucleic acid may be single stranded or double stranded structure. The nucleic acid is found in the center of the virus, and the protein forms a coat around it. It is the protein coat that attaches to a host cell and the virus thrives in the cell. The nucleic acids help in reproducing of new viruses.

Characteristics of Viruses

Viruses cannot live freely in nature. Viruses are highly specific in nature; they attack only certain tissues in one kind of host. They are inactive in state and once they enter any host cell, they become active. Viruses do not have their own cell, and do not have machinery required for reproducing. They use host cell's metabolism and start multiplying producing more viruses thereby killing the host cells. The newly produced virus particles then attack new host cells.

Diseases caused by Viruses in Man

The diseases caused by the viruses are colds, influenza, mumps, measles, chickenpox, pneumonia, polio, herpes, rabies, chikungunya, Ebola, Zika, AIDS, dengue, SARS ( Severe acute respiratory syndrome) and MERS ( Middle East respiratory syndrome are caused by new types of coronaviruses. The harmful viruses are known as virulent. Corona virus is the most recently discovered viruses. This corona virus causes the disease COVID-19. It is caused by the severe acute respiratory syndrome coronavirus 2 (SARS-Cov-2). The world is going through turbulent times due to this COVID-19 disease that has led to a pandemic 2020 presently.

Symptoms of Diseases caused by the Viruses in Man

Viruses cause a wide range of symptoms that includes fever, cough, sore throat, head ache, pneumonia body pains and aches. They also cause irritability, rashes, gastrointestinal disturbances, runny nose, nausea, diarrhea and vomiting. Symptoms may vary from person to person depending on varied factors related to health history of the person. Viral respiratory diseases are infectious and spread quickly through cough and sneeze from an infected person.

Diseases caused by Viruses in animals

The diseases caused by viruses are are foot-and-mouth disease of cattle, rabies in dogs, swamp fever- horse disease caused by retrovirus, swine pox disease of pigs, jaundice of silkworms, JapaneseB- Encephalitis disease in pigs, sheep, birds and man, caused by flavivirus, fowl pox poultry disease caused by Poxviridae, Cow pox disease caused by cowpox virus, and hog cholera.

Symptoms of diseases caused by Viruses in Animals

The symptoms in animals includes high temperature, breathing difficulty, discharge of blood through openings like nose and mouth, loss of appetite, blisters in mouth lameness, swellings in body parts, salivation and sudden death of animals

Diseases caused by Viruses in Plants

The virus's diseases in plants are tobacco mosaic virus in tobacco, potato, cucumber and egg plants, tomato bushy stunt, beet curly top and aster yellows, barley yellow dwarf disease in wheat plants, leaf curl virus in tomato, papaya, capsicum.

Symptoms of Virus diseases in Plants

Viral disease symptoms in plants are crinkled leaves, yellowed leaves, plant stunting, mosaic leaf,ring spotting. Infected plants may also show abnormal growth, drying of roots, some of the plants may show outgrowths in form of hairs, leaf rolling etc.

Precautions to be taken to prevent Virus Diseases

Taking care of personal hygiene is very important. Cover the mouth and nose with a mask. Eat hot and freshly cooked food to stay healthy. Include fruits and vegetables to boost your immune system. Wash hands frequently with soap and water. Avoid touching of your face parts, eyes, nose and mouth to prevent entry of virus. Maintain social distance from an infected person. Some of the diseases are controlled by vaccination. Get vaccinated for prescribed diseases recommended by the doctors. Viruses gives rise to new types by mutation, new vaccines are needed to prevent the spread of the diseases.
Drink plenty of water to be hydrated and take adequate rest and sleep. Using sanitizer is one way of preventing the bacterial and virus diseases. Sanitizers dissolves the outer coating of the organisms and kills them. Keep a clean environment around you and use proper disposal system to discard waste materials. Do not allow water to collect in and around the house. Breeding of mosquitoes can be controlled by fumigation of houses and the surrounding areas. Scientists are continuously working in developing vaccines for varied forms of diseases. Be informed about the virus diseases and take adequate precautions to stay healthy. Have a positive attitude and be physically active.

Culturing of Viruses

Viruses are cultured scientifically in the laboratories by scientists in controlled settings. Virus culture helps in studying the virus structure, identification of virus type, its features, structure, growth and other aspects related to disease control and prevention of virus diseases. In this scientific method the virus samples are placed in laboratory containers or dish. It is observed for several days and monitored for their growth. Analysis is done, recorded and reports are prepared, then sent to respective departments. Culturing of viruses are difficult processes as viruses need living cells for their multiplication.

Droplet infections or air borne diseases of Viruses

Respiratory infections spread through droplets in air. Hence the name droplet infections or airborne disease as they spread through air. An infected person carries the disease germs in his nasal passage, throat and mouth. When the person sneezes or coughs the droplets of germs enter into the air and a healthy person gets infected when he/she inhales the air containing these germs.


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