viral diseases

VIRAL DISEASES

Viral diseases

Chikungunya

It is a temporarily debilitating disease caused by Alphavirus and spread through mosquitoes, Aedes aegypti

and Aedes albopictus (Tiger Mosquito). Monkey and some humans function as reservoirs. The name chikungunya is derived from Bantu or Makondo language of Africa which means "bent up" because of stooped posture of patients caused by development of arthritic symptoms. It has appeared in good number in India during 2006 with 13,27,636 reported cases and 70 confirmed deaths. The patient has maculopapular (stains and eruptions) rash on limbs and trunk, and arthritis of multiple joints. There is fever (120°F or 39°C) which lasts for about two days. It is accompanied by conjunctivitis and photophobia. Even after disappearance of fever, headache insomnia prostration and arthritis continue for 5-7 days. Chloroquine phosphate has been found to reduce the impact of the disease. Protection against Aedes mosquitoes by use of long sleeves, full pants, socks, windows and doors with wire gauze screens and mosquito repellents are preventive measures. There should be no stagnant water (e.g., coolers) nearby.

Poliomyelitis/Infantile Parmlysis/Polio

It is highly infectious viral disease of infants and

children (hence infantile paralysis) that may attack adults also. Causal agent is a very small RNA containing Polio Virus. Disease is transmitted through faeces, urine and nasal secretions contaminating food, water, drinks, either directly or through flies with an incubation period of 5-17 days. During incubation period, the virus multiplies in alimentary canal. Then it passes to lymph, blood and finally central nervous system in dorsal horn cells of spinal cord and brain stem. Preparalytic stage (1-4 days) is characterised by fever, sore throat, nausea, vomiting, diarrhoea, headache, stiff back, stiff neck, twitching and convulsions. During paralytic stage, motor nerves are affected resulting in atrophy of muscles, generally of arms and legs but may affect those of diaphragm (only iron lung can save), larynx and pharynx (fatal). Vaccine (Salk's vaccine),

Influenza/Flu






Influenza is endemic, epidemic and pandemie. Endemic influenza is localised. It is caused by a Gram negative bacterium Haemophilus influenza. Epidemic influenza spreads throughout the area while pandemic influenza spreads over wide geographical regions. It is viral in origin, occurs in certain regions after every 1-3 years, while globally it recurs every 10-15 years. Asian flu is viral influenza which originated in China in 1957. Influenza virus or Myxovirus influenza is a ribovirus with fragmented genome. It has three forms A, B and C. Mutation rate is high. Certain strains are potent killers. For example, Spanish Flu (1918) claimed 20 million lives. Influenza causes inflammation of upper respiratory tract, nose, throat and eyes. It results in coryza (profound discharge or running nose), sneezing, sore throat, coughing, muscle pains, headache, chill and fever for 4-5 days. Influenza is highly infectious. Incubation period is 2-3 days. Complications include development of bronchitis, ear infection and pneumonia. The disease spreads through direct contact, unclean hands and droplet method. However, it can also attack humans directly from birds e.g., chicken to human beings in Hong Kong (1997). Reservoir is pig which gets it from Water Fowl. Vaccine is available against influenza virus A.

Common Cold/Rhinitis

It is one of the most common infectious diseases of humans which is caused by some 100 types of Rhino viruses, Corona viruses and small bacterium Dialister pneumosintes. The pathogens do not reach the lungs. They infect nose and upper respiratory passage causing inflammation of mucous membranes. There is initation of nasal tract, nasal congestion, flow of mucus, sneezing, sore throat, hoarseness, cough, tiredness, headache and slight fever. Some persons also suffer from allergic rhinitis. Common cold spreads through droplets from talking and sneezing, direct contact, hand shake and common articles of use like pens, pencils, books, cups, door handles, computer key board, computer mouse, etc. It cures automatically after 3-7 days. Medicines are taken to reduce severity of nasal irritation and clearing nasal tract.

Yellow Fever

It is viral fever transmitted from infected

humans (urban type) and infected animals (jungle type) by mosquitoes in tropical Africa and America. The virus is called Flavivirus. It has both mild and sever forms. In sever form it causes fever, hemorrhage, jaundice and renal demage. In mild form it produces fever with inapparent infections. Aedes and Haemagogus mosquitoes act as vectors.

Dengue Fever

It is a viral disease which is caused by viruses DEN-1, DEN-2, DEN-3 and DEN-4, and spread by female Tiger Mosquito or Aedes aegypti and related species. Once infective, the mosquito remains
infective for life. Dengue is of two types:-  
(I) Classical Dengue Fever (Break Bone Fever). It is more severe in adults, starting with mild conjunctivitis or coryza but within hours the patient has high fever, retro-orbital pain, severe splitting headache which increases with movements, backache, breakbone or
joint pains, muscle pain and chill with or without pin-sized vesicles on hinder part of soft palate and rashes on inner side of arms, chest and back. The disorder persists for 5-7 days. It can recur in mildform. 

(ii) Dengue Haemorrhagic Fever (DHF). It is fatal form that starts with fever (101°-105°F), nausea, headache, vomiting, abdominal pain, palpable liver, cold extremities with haemorrhage spots (also on fore-head), internal bleeding leading to blood in stool, urine and vomiting. Blood platelet number falls below 70,000/mm3. It leads to dengue shock syndrome with rapid weak pulse. Paracetamol with replenishment of blood platelets may be helpful. Aspirin and dispirin are harmful. Dengue occurred in India in 1988, 1996 and 2015. In 1996 over 400 persons died of the disease. Vaccine has been developed in Thailand against the disease.

Chicken Pox

It is a contagious and fomite transmitted eruptive viral disease which is more common but less severe in children of upto 10 years and severe but rare in adults. winter and spring are chicken pox time.

The disease is caused by virus varicella zoster with incubation period of 14-16 days. Illness begins with slight fever, shivering and backache. There are then prodormal or transitory rashes with crops of pinkish centripetal spots appearing first on trunk, fore-head and face. Uneasiness, aches and high fever accompany each new crop. Spots turns into fluid filled vesicles and then scabs in five days. Scabs fall off without leaving any mark. Use of boric acid, calamine and benzyl benzoate reduces itching and tendency to scratch. No drug, no vaccine. Antibiotics are given for covering any complication. Passive immunity is possible through zoster immunoglobulins. Single attack gives life long immunity.

Small Pox

It is an eruptive viral disease which has been completely eradicated through widespread compulsory vaccination (10 year Global

Eradication Programme by WHO starting 1966). The last case was reported in Somalia in 1977. WHO declared the planet free from small pox in 1980. The disease is caused by brick-shaped DNA virus called Variola Virus. Infection spreads from oral, nasal, vesicular discharges, pustules and scabs. Incubation period is 12 days. The disease begins with headache, backache, chill, high fever, rashes appearing on third day of illness as reddish spots which change into papules, vesicles, pustules and finally scabs in third week. The spots appear first on the hair line, then face followed over rest of the body but fewer on the trunk. The scabs fall down leaving permanent pox marks, especially over face. Complications include blindness. Death could occur. First vaccination developed by Edward-Jenner (1796) wae against small pox. Disease used to spread through coughing, sneezing and fomite transmission.

Hepatitis (Gk. Hepaticus-liver, itis-inflammation) It is an infectitious disease characterised by inflammation of liver. Hepatitis usually results in blockage of biliary excretion and production of jaundice. Jaundice is a syndrome of hyperbilirubinemia (excessive concentration of bilirubin in blood) and deposition of bilirubin in skin, mucous membranes and sclera resulting in yellow appearance of patient or icterus. Hepatitis is of two types, viral and toxic. Viral hepatitis is caused by viral infection. It is of five types-A, B, C, D (delta) and E.
Hepatitis A

It is also called inflectious epidemic hepatitis or epidemic jaundice. The disease is caused by Hepatovirus or hepatitis A virus (HAV). It is a small sized (27 nm), naked, icosahedral virus which contains a linear single stranded RNA. The virus can withstand heating at 56 degree Celsius for 30 minutes as well as many disinfectants. It is transmitted by faecal-oral route by food, drink or contact. Incubation period is 30 days (15-50 days). In India, the infection commonly occurs in children upto age of 15 years due to poorer hygienic conditions but the disease can occur at any age. Immunity occurs thereafter. A carrier stage is absent. Recovery takes 8-12 weeks. The disease is self limiting. The patient begins to pass HAV in stool even before the onset of symptoms. The virus multiplies in intestinal epithelium. It ultimately reaches liver through blood. There is brief influenza-like illness with fever, malaise, nausea, vomiting, anorexia and liver tenderness. pain may occur in right upper abdominal quadrant. It leads to jaundice. Hepatitis A is, therefore, also called catarrhal jaundice. Diet control and bed rest are required. Antibiotics are given to prevent secondary infection. Since infection can spread from one Person to another, complete hygienic conditions must be observed. Fatality is less than 0·5%. Short term protection can be obtained through injection of immunoglobulin. Vaccine is also available but is Costly.

Hepatitis B


It is popularly called serum hepatitis or transfusion hepatitis. The disease is caused by hepatitis B virus or HBV. It is also called Dane particle. The virus is spherical and double shelled. Genetic material is circular dsDNA. Mature virus has a size of 42 nm. Two subvirion morphological forms are also formed. They are 22 nm diameter spherical and tubular. Virus occurs in blood and body fluids (saliva, mother's milk, semen, vaginal secretion). Therefore, infection can spread through kissing, sharing of safety razor, needlestick injury, use of contaminated needles and syringes, ear and nose
piercing, tatooing, sexual contact, etc. Average incubation period is 90 days (40-180 days). Patient develops malaise (feeling of fatigue), weakness, myalgia (pain in muscles), anorexia, vomiting, pain in right upper abdominal quadrant, pale stool, brownish urine and jaundice. Fatality is less than 1%. Complete recovery occurs in 90-95% cases. Others develop liver complications like active hepatitis,cirrhosis and hepatocellular carcinoma. Even after recovery, many individuals become carrier. Infection can be tested by presence of antigens HBsAg (surface or Australian antigen), HBcAg (core antigen) and HBeAg ('e'antigen). Bed rest, fat free diet and antibiotics are required for protection against aggravation Contact with body fluids should be checked. Vaccine is available. A drug from Phyllanthus amlarus provides relief.

Hepatitis C








It is similar to hepatitis B in being serum or transfusion hepatitis which spreads through needlestick injury, cuts, contaminated needles and syringes, sexual contact, contaminated blood, etc. The virus HCV has single stranded positive RNA. Incubation period is 6-8 weeks but may require several months. Majority of infections are subclinical with milder symptoms, little or no jaundice. As a result the disease remains unattended. It often becomes chronic leading to liver damage, cirrhosis and hepatocellular carcinoma.

Hepatitis D (Delta Hepatitis)

It is caused by simultaneous infection of HBV and delta virus HDV. Delta virus is spherical, 36-38 nm in diameter. It has single strtnded small circular minus sense RNA. The genome can encode only for its nucleoprotein but not the capsid. The latter requires genome of HBV. The support provided by HBV in forming HD virion is called piggy backing. HBV carriers are the worst sufferers
as delta virus can replicate without any long interval. Symptoms are similar to those of hepatitis B but
are more severe and cause large scale damage. Mortality is 20%.

Hepatitis E


It is enterically transmitted non A, non B hepatitis (HNANB). The virus is naked and spherical with a diameter of 27-38 nm. It possesses a single positive stranded RNA. Capsid has characteristic surface depressions. Quite a sizeable number of epidemie, endemic and even sporadic hepatitis cases are due to it. Hepatitis E was first recorded in 1955 in Delhi when some 29000 cases were identified. Like hepatitis A, hepatitis E spreads through faecal contaminated water and food.
Incubation period is 5-6 weeks (2-8 weeks). Symptoms are similar to those of hepatitis A but bilirubin levels are usually higher. Jaundice is deeper and prolonged. Fatality rate is 0·5-3·0% but 10-20% in pregnant women. Carrier stage is absent. Personal cleanliness, boiled water, properly heated, cooked and clean food articles and control of flies are required in period of epidemic. Vaccine is available.

German Measles

It is milder form of measles which occurs in all age groups and is caused by Rubella Virus. Rash appears on fore-head, face and then other body parts. It is accompanied by mild conjunctivitis, headache, swelling of lymph glands (especially posterior cervical) and fever. The disease is harmful if it occurs to pregnant women as it is transferred to foetus through placenta (congenital rubella) resulting in eye defects, deafness and cardiac problems. Immunoglobulins are useful. Vaccination is provided as MMR.

Rabies/Hydrophobia





It is a fatal viral disease (Rabies or Rhabdo Virus) that is transmitted to human beings by biting/saliva of rabid dog or cat. A number of wild animals also carry the virus, e. g., jackals, wolves,
foxes, mongoose, bat, skunk, coyote (prairie wolf) etc. Incubation period is 1-3 months. Multiplication occurs in neurons (nourotrophic). It leads to encephalitis, fear of water, severe headache, high fever, alternate excitement and depression, spasm of throat and chest leading to death. Bitten person should be immediately administered vaccine that develops antibodies before the virus becomes active. The vaccine was developed by Louis Pasteur. Earlier it consisted of 14 inoculations but now 6 doses of vaccine are administered. Dog should be watched for 10 days for the development of rabies symptoms(Running amuck, change of voice, excessive salivation). Stray dogs and cats must be eradicated while pets should compulsorily be immunised. Pre-exposure vaccine is given to forest rangers and naturalists.

Toxic Hepatitis
It is hepatitis or jaundice caused by toxic chemicals called hapatotoxins. The toxins damage or destroy liver cells, e.g., Amanita toxin, carbon tetrachloride, yellow phosphorus, alcohol and some drugs. They many enter the body from any route.

Measles
It is a highly infectious eruptive viral disease of children below the age of five and caused by RNA-containing Rubeola Virus/polynosa morbillorum. Disease is transmitted by 


contact, fomite and droplet methods. Portal of entry is respiratory tract and conjunctiva. Incubation period is 10-14 days. In preeruptive stage (3-4 days), there is hoarseness, cough, sneezing and running nose or coryza due to inflammation of respiratory tract, redness or watering of eyes (conjunctivitis), loss of appetite and fever. Blue-white Koplick's spots (with reddish base) appear opposite molar teeth in buccal cavity on third day. Fourth day begins with itching, skin rash, small raised red spots (rubeola) in crescent shaped groups starting from back of ears, reaching fore-head, face (bloated and blotchy) and then body. By 5-6th day the rashes begin to subside. Antibiotics and vitamin A are given to prevent complications, Vaccination (MMR or Mumps Measles and Rubella) is available which is given at the age of one. Prior to that the infant carries passive immunity from mother.

Mumps
It is an acute infectious one time viral disease of school going children which is characterised by
swollen parotid salivary gland, hence infectious parotitis. Adults without previous infection may
catch the disease. The pathogen ie RNA-containing Paramyxo/Mumps Virus. It is transmitted by direct
contact, droplet method and fomite method. Incubation period is 12-26 days. Due to mumps the
patient has difficulty in swallowing and opening of mouth. There is high fever, chills, headache,
malaise (general body aches), anorexia (loss of appetite). Secondary infections are common especially in
adulte-pancreatis (pancreas), meningo-encephalitis, mastitis (mammary glands), myocarditie (heart),
orchitis (male gonads), saphingo-oophoritis (fallopian tube and ovary). The last two result in infertility.
Antibiotics are given to prevent secondary infection. Vaccination is available (MMR-mumps, measles
and rubella/German measles