Viral infection is caused by viruses, which are a type of micro-organism. Viruses are made of DNA and RNA made up of long protein molecules, which are enclosed in a protein envelope known as capsid. Viruses rapidly multiply within living cells of animals, plants and microorganism such as bacteria and parasites. Viruses are known to cause several illnesses called viral infections. It is important to understand about viral infections, the classification of viruses, the diseases caused by them and the symptoms of common viral infection.

How Does Viral Infection Spread?

How Does Viral Infection Spread?

Viral infections are often contagious and easily spread through various routes. Spread of viral infection results from discharge of viruses through sputum, body secretions, gastric secretions like vomitus and feces as well as urine. The virus is transmitted from plants, animals and humans to another living organism through discharged skin, breathing, sputum, vomitus, touch and contaminated urine as well as feces. Viral infection is transmitted through contaminated clothes, paper towels, sexual contact and sharing of personal objects as well as used needles.

Viruses rapidly multiply within the cells, which results in viral infection. Viruses change the protein molecule configuration, which often follows recurrent infection and higher resistance. Viruses replicates within epithelial cells of nasopharynx, lymph nodes, conjunctiva, intestine and reticuloendothelial cells. Rhinovirus multiplies in nasal mucosa and cervical lymph node. Hepatitis virus is multiples in the intestine and liver.

Viral infections in the body or the attack of viruses can be eliminated by white blood cells. The increased number and higher efficiency of white blood cells help to fight the viral infection. The white blood cells help to produce antibodies against the viruses, which help to resolve the viral infection.

Most mild viral infections resolve on their own within a week. Viral infections, which appear in many types, can be managed effectively with medications and adequate rest. Medications that treat viral infections and vaccines that prevent them aim at improving the immunity of the person to fight against viruses.

Viral Infection – Classification of Viruses

Viral infections are caused by a variety of viruses, classification of which is mentioned here. There are several viruses found in lab studies. The classification of viruses most accepted were described by Noble price winner David Baltimore. The classification of viruses depended on changes within RNA and DNA protein molecules

Baltimore Classification of Viruses

  1. ds-DNA viruses: Adenovirus, Herpesvirus, and Poxviruses
  2. ss-DNA viruses: Parnoviruses
  3. ds-DNA viruses Hepandnaviruses
  4. ds-RNA viruses: Reoviruses
  5. ss-RNA viruses (-): Orthomyxoviruses, Rhabdoviruses,
  6. ss- RNA viruses (+): Picornavirus, Togaviruses
  7. ss-RNA RT viruses- Retrovirus

Adenovirus: Keratoconjuctivitis

Ds- DNA virus is known as adenovirus. This viral infection infects the mucosal membrane of respiratory tract and conjunctiva. The infection results in rhinitis, pharyngitis, bronchitis and keratoconjuctivitis.

Parnovirus: Slapped Cheek Disease

ss-DNA viruses causes the slapped cheek disease. The paronovirus infection is less common in adults but often seen as a mild viral infection in children. The infection in children is also known as slapped- cheek disease because of significant rash observed over the face. This viral infection often ends in serious complications when occurs in an adult.

Hepandnavirus: Hepatitis B

Hepandinavirus is classified as ds-DNA viruses. The hepandanvirus is also known as hepatitis B virus. The viral infection causes hepatitis and transmitted through body fluids like blood or semen. Source of transmission of infection is contaminated blood, exchange of contaminated needle and sexual contact.

Reoviruses

ds-RNA viruses infect human, animals and plants. In humans, virus attacks mucosal membrane of respiratory and gastrointestinal system. Symptoms of Reovirus are often mild and last for 3 to 7 days. Virus spreads in almost all body fluids like blood, cerebrospinal fluid (CSF), feces and respiratory tract secretions.

Orthomyxovirus: Influenza

ss-RNA viruses are the cause of seasonal periodic upper respiratory tract infection. Influenza is caused by Orthomyxovirus. There are several subtypes of influenza virus broadly divided in 3 groups. Influenza virus A, B and C causes influenza like disease in humans.

Picornavirus:

ss-RNA viruses have several subtypes. Most subtypes of piconavirus are known as poliovirus, rhinivirus, coxsackievirus, echovirus, enterovirus, rhinovirus, and heptovirus. Picornavirus causes polio, hepatitis A, meningitis and encephalitis. Each subtype of picornavirus is further classified into several subtypes. Piconavirus affects almost all organs resulting in conditions like conjunctivitis, meningitis, endocarditis, myocarditis, hepatitis, gastroenteritis and bronchitis.

Retroviruses

ss-RNA RT viruses has several subtypes but most severe life threatening infection observed are HIV (human immunodeficiency virus) disease. HIV is also known as AIDS. In this illness, lowered immunity, results in recurrent serious infections, which affects the person's health.

Symptoms of Viral infection

Some of the common symptoms of viral infections include fever, fatigue, headache and body pain. In addition to these, specific symptoms depending on the type of viral infection are also noted. These include cold, cough sore throat, abdominal pain, indigestion, nausea, vomiting, diarrhea and other gastric disturbances, soreness of eyes and itching or rash over the body. Viral infections affecting the skin show varying types of skin lesions.

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Written, Edited or Reviewed By:

, MD, FFARCSI

Last Modified On: July 6, 2017

Pain Assist Inc.

Pramod Kerkar
  Note: Information provided is not a substitute for physician, hospital or any form of medical care. Examination and Investigation is necessary for correct diagnosis.

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