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List of Important Viral Diseases
Chickenpox and Shingles
Chicken pox (varicella) is a highly contagious childhood skin-diseases caused by varicella zoster virus (VZ-virus), a member of the family Herpesviridae. The virus is transmitted by infectious especially when susceptible individuals are in close contact. The virus enters the respiratory tract, multiples and is quickly disseminated via the blood stream (incubation period of from 10-23 days) resulting in small vesicles appearing on the face or upper part of the body. These vesicles fill with pus, rupture and become covered by scabs Healing of vesicles takes place in about 10 days and there is intense itching during the period. An attenuated varicella vaccine called ‘Varivax’ or the drug acyclovir (Zovirax or Valtrex) help preventing or reducing the infection.
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Chickenpox Pathogenesis
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The chicken virus may remain dormant (latent) in nerve cells for years. These latent viruses may become activated in immunosuppressed or elderly individuals, migrate from nerve cells (virus-reservoir) to the skin surface, multiply and cause a painful skin eruption called shingles (zoster), a reactivated from of chickenpox. Most cases of shingles (zoster) take place in people over 50 years of age. Acyelovir (Zovirax or Veltrex), Vidarabine (Vira-A) or famciclovir (Famvir) are recommended to treat the disease.
Influenza (FLU)
Influenza or the flu is a respiratory system disease diseases system caused by influenza-viruses.
Human influenza virus is transmitted from one person to the other through the air droplets expelled during coughing an sneezing. The virus infects the mucous membranes of the upper respiratory tract and occasionally invades the lungs.
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Symptoms include a low grade fever lasting for 3-7 days, chills, fatigue, headache and general aching. Recovery usually takes place rapidly. The antiviral drugs amentadine, rimantadine, zanamivir and oseltamivir has been shown to reduce the duration if administered during first two days of illness.
At present, three influenza A virus subtypes are epidemic in humans (H1N1, H2N1 and H3N2). Ifluenza infections frequently occur during winter and the school going children are more susceptible to the diseases.
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Common Cold
Common Cold (coryza : Gr. Koryza = discharge from the nostrils) is the most frequently occurring viral disease in the human beings caused by rhinoviruses (ssRNA viruses) belonging to family Picornaviridae. Local inflammation of the upper respiratory tract and the release of mucus secretions accompanied by sneezing and sometimes coughing characterize it. The etiological agents in adults are rhinoviruses. There are more than 100 immunologically distinct types of rhinoviruses that are capable of causing common cold. The initial viral infection is generally followed by secondary bacterial infection of respiratory tract. There is no specific treatment for common cold as it is self-limiting clinical syndrome. The recovery takes place within on week by action of natural defense mechanism of the body.
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Measles (Rubeola)
Measles, also called rubeola (L. rubeus = red), is highly contagious skin disease occurring in young children. It is endemic throughout the world. The measles virus is a member of the genus Morbilli-virus belonging to family Paramyxoviridae. The virus multiplies in the upper respiratory tract from on where it disseminates to lymphoid tissues for further multiplication. It involves number of organs and cause death of patient. The disease is characterized by eruption of skin rash, after 14 days of exposure to measles virus. It first appears behind the ear and rapidly spreads throughout the body. Treatment is usually supportive, i.e., physical rest and intake of sufficient fluids. However, complication can occur due to secondary bacterial infection and chemotherapeutics are required to be given. Measles can be prevented by childhood immunization.
Mumps
Mumps is also childhood diseases. The mumps virus is a member of the genus Rubalavirus in the family Paramyxoviridae and is pleomorphic enveloped virus containing ribocucleic acid-protein core. The virus is transmitted via contaminated droplet of saliva. The disease is characterized by swelling of one of the saliva glands and subsequently the other gland. The swelling of glands is reported after 18 days of incubation. Symptomatic management of patient includes adequate hydration, analgesic and antipyretic theraphy. Live attenuated mumps virus vaccine is available for prophylactic use.
Poliomyelitis
Poliomyelitis (Gr. Polios = gray; myelos - marrow or spinal cord), polio or infantile paralysis is caused by the poliovirus which enters the body through ingestion of contaminated water and food. The viruses multiply within the mucosa of the throat and/or small intestine from where they get disseminated via blood stream into lymphatic tissues and further multiply. Viruses cross the blood brain barrier and multiply in the neural tissues causing varying degrees of damage. Headache, vomiting constipation and sore throat characterize the diseases. The disease is more prevalent during childhood and causes infantile paralysis. Immunizing children with Salk and Sabin polio vaccine can prevent the disease.
Hepatitis
Hepatitis (Gr. Hepaticus = liver) is a liver inflammation caused by an infectious agent. Although many viruses and a few bacteria can cause hepatitis, a restricted group of viruses is often associated with it.
Hepatitis virus
| Disease |
Virus and Genome |
Vaccine available or not |
Hepatitis A |
Hepatovirus (HAV); ss-RNA |
Yes |
Hepatitis B |
Orthohepadnavirus (HBV); ds-DNA |
Yes |
Hepatitis C |
Hepacivirus (HCV); ss-RNA |
No |
Hepatitis D |
Deltavirus (HDV); ss-RNA |
No |
Hepatitis E |
Calciviridae family (HEV); ss-RNA |
No |
Hepatitis G |
Flairviridae family (HGV); ss-RNA |
No |
All the hepatitis vaccines defined are not related to one another but all infect liver cells resulting in various types of hepatitis. Symptoms of hepatitis include fever, jaundice (production and release of excess bilirubin by the liver due to destruction of liver cells, resulting in yellowing of the skin and whites of the eye), lever-enlargement (hepatomegaly) and breakdown of the normal liver architecture with fibrosis (cirrhosis).
Availability of vaccines. However, most treatment of hepatitis is supportive, providing rest and time to allow liver damage to resolve and be repaired. Interferon - a is effective in hepatitis C (i.e. HCV) when given in combination with ribavirin.
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