Diseases Caused By Virus

Acquired immuno-deficiency syndrome (aids)

Acquired immunodeficiency syndrome (AIDS or aids) is caused by the human immunodeficiency virus, or HIV. This virus belongs to a group of viruses called retroviruses.HIV gradually reduces the efficiency of the human immune system, it destryos the body’s ability to fight diseases. This makes the body vulnerable to other life-threatening diseases that finally cause the patients’s death.

HIV attacks the helper T-lymphocytes (or T4 cells–a type of leucocyte). In the first stage of infection, the virus grows and multiples in these cells.

After some time, the virus starts destroying the T4 cells. T4 cells produce antiobodies to fight microorganisms that invavde the body. So, when they are destroyed, the body is uable to fight infections. This is the final stage of the infection, and the infected person is now siad to have AIDS.

The patient easily catches infections such as pneumonia and often develops various forms of cancer.

Incubation period is uncertain, varying from a few months to 10-12 years.

Symptoms

• Short flu-like illness.
• Chronic diarrhoea and severe weight loss.
• Swollen lymph nodes.
• Decreased count of blood platelets causing blood loss.
• Development of a disfiguring form of skin cancer (Kaposi’s sarcoma).
• Sweating at night.
• Severe damage to brain, leading to loss of memory and ability to think and speak.
• Due to breakdown of immune system, the victim becomes susceptible to other infections.
• HIV thus causes immunogenic imbalance.
• Immune system collapse and patient die due to uncontrolled secondary infections.
• Swollen lymph nodes, prolonged mild fever, diarrhoea.
• Advance stage is characterised by one of 24 specific opportunistic infections; common are - Pneumocystis carinii pneumonia(PCP) and Kaposi’s sarcoma(KS), type of skin cancer.

Transmission

The disease is transmitted from an infected person to a healthy person through :

• Sexual contact and infected blood contact, (blood transfusion) are common means of transmission.
• Use of contaminated needles, syringes, blades or razors.
• Through cuts and wounds during close contact between infected and non-infected people.
• From infected mother to foetus through placenta and through breast feeding.
• Homosexual relationship and sharing of needles for drug abuse are high risk groups.

High risk groups include

• People having sex outside marriage.
• Homosexuals and bisexual males having both homosexual and heterosexual relations.
• Drug users.
• People often seeking blood transfusion.

Prevention and Control

• Education of the masses.
• Use of clean sterile needles and syringes and preferably disposable ones.
• Use of HIV-negative blood for blood transfusion.
• Avoiding sex outside marriage and use of condoms.
• Use of common razors at the barber’s shops should be avoided.
• HIV is a fragile virus, does not survive for long outside body, dies during dishwashing, cloth washing. If exposed to 135°F (56°C) temperature for 90 minutes the virus dies.
• Till date, there is no effective treatment for AIDS.

INFLUENZA (FLU)

Highly infectious respiratory disease.

Commonest site of infection is epithelial (or mucous) lining of nose, throat and upper respiratory tract.

Pathogen :Orthomyxovirus,a group of myxo viruses, mainly Myxovirusinfluenzae.

Incubation period :24-72 hrs.

Symptoms :

• Fever,chill, cold and sneezing,coughing
• Mucus and watery discharge from nose; headache and fever.
• Muscle aches, inflammation of respiratory mucosa.
• Extreme conditions are pneumonia, bronchitis and ear infection.

Transmission is mainly from person to person by droplet infection (through coughing, sneezing, spitting). Overcrowding helps in the rapid spread.

Prevention and Control

• Keep away from influenza patients.
• Though prevention is possible only by the use of a vaccine, this is not easy, as several different viruses cause the disease, and a vaccine prepared from one virus does not provide protection against the ulcers.

Treatment : No medicines available but vaccination reduces the incidence.

POLIO (POLIOMYELITIS)

It is very frequent in children.

Pathogen :Polio virus (smallest known virus)

Mode of transmission :Disease spreads through the intestinal discharges of the patient. It may also spread through food or drinks contaminated by flies.

Incubation period :7 to 14 days.

Symptoms :

• When the virus enters the digestive tract, it multiplies, and then passes to the bloodstream, and finally reaches the spinal cord. The virus causes inflammation of grey matter of the spinal cord, inability of the head to bend forward and stiffness of the neck.
• It also destroys motor nerve cells on the spinal cord. Muscles fail to work due to lack of nerve impulses. This may cause paralysis of limbs.

Prevention

• Screening of food from flies and safe disposal of pharyngeal and bowel discharges of the patient, as they have polio viruses. OPV (Oral Polio Vaccine) is an effective preventive vaccine.
• These day Polio vaccines are given to children below 5 year age group at National Level Campaign.

RABIES

A type of rhobdovirus causes rabies, which is highly fatal disease of the central nervous system. Rabies is also known as hydrophobia.

Pathogen :Rabies is caused by a virus (Lyssavirus type 1). Rabies virus is commonly called is street virus.

Incubation period :10 days to 1 year.

Transmission

• An animal affected by the disease is called rabid.
• Rabies in human beings is generally caused by a rabid dog. It may also be caused by the bite of rabid wolves, jackals, cats, etc.
• The virus is present in the saliva of infected animals.

Symptoms

The virus after reaching the nervous system, first stimulates the nervous system and then damages the cells of the spinal cord and the brain, and finally results into extreme excitation and

• High fever
• Severe headache
• Pain or itching at the site of the bite.
• Painful contraction of muscles of throat and chest.
• Patient suffers from anger, irritation, depression and fear of death.
• There is restlesness, choking feeling and difficulty in taking even liquid food.
• The patient develops a fear of water, for this reason, the disease is also called hydrophobia.
• Severe damage to central nervous system causes paralysis and painful death.

JAUNDICE AND HAEPATITIS

Jaundice is a serious communicable disease in which liver is affected. It is caused by a virus. The most obvious symptom of this disease is the yellowing of eyes, skin and nails. The yellowing is because of the presence of excessive bilirubin (a bile pigment) in the blood.

Haepatitis is also a serious communicable disease. Hepatitis (Gk. hepato= liver; itis= inflammation) involves the inflammation of liver cells leading to cirrhosis of liver and yellowness of skin and eyes. It is a viral disease and is very serious disease as it causes so many deaths in only one day as by AIDS virus in one year.

There are different types of haepatitis :

• Haepatitis A, B, C, D, E and G.
• Haepatitis A is caused by haepatitisA virus (HAV); similarly, haepatitis B is caused by haepatitis B virus (HBV).
• Haepatitis B is a serious disease causing liver damage; however, haepatitis A is not a serious health problem in India.
• Haepatitis is common in children and young adults.

Symptoms

• Fever, chill, headache and joint pain.
• Above symptoms are followed by nausea, vomitting, dark urine and jaundice.
• General weakness and loss of appetite.
• Irritating rashes.

Transmission

• Haepatitis A is spread either by direct person to person contact or indirectly by way of contaminated food, water or milk. It is also transmitted sexually, mainly among homosexuals.
• Haepatitis B, on the contrary, is essentially a blood-borne infection. It is transmitted through blood transfusion, dialysis, contaminated syringes, pricks of skin, etc.