1. Chicken pox

Pathogen: Chicken pox virus (voricella)

Mode of transmission: By contact or through scabs

Incubation period: 12-20 days


  1. Fever, headache and loss of appetite
  2. Dark red-coloured rash on the back and chest which spreads on the whole body. Later, rashes change into vesicles.
  3. After few days these vesicles start drying up and scabs (crusts) are formed.
  4. These scabs start falling (infective stage) 

Prevention and cure

There is no vaccine against chicken pox as yet. But precautions must be taken as follows:

  1. The patient should be kept in isolation.
  2. Clothings and utensils, used by the patient should be sterilized.
  3. Fallen scabs should be collected and burnt.

One attack of chicken pox gives life long immunity to the person recovered from this disease.

2. Measles

Pathogen: Virus (Rubeola)

Mode of transmission: By air

Incubation period: 3-5 days


  1. Common cold
  2. Appearance of small white patches in mouth and throat.
  3. Appearance of rashes on the body.

Prevention and cure

  1. The patient should be kept in isolation.
  2. Cleanliness should be maintained.
  3. Antibiotics check only the secondary infections which can easily recur.

3. Poliomyelitis

Pathogen: Polio Virus

Mode of transmission: Virus enters inside the body through food or water.

Incubation period: 7-14 days


  1. The virus multiplies in intestinal cells and then reaches the brain through blood.
  2. It damages brain and nerves and causes infantile paralysis.
  3. Stiffness of neck, fever, loss of head support.

Prevention and cure

  1. Polio vaccine drop (oral polio vaccine, OPV) are given to children at certain intervals.
  2. Pulse polio programme is organised in India to give polio vaccine to children.

4. Rabies (hydrophobia)

Pathogen: Rabies virus

Mode of transmission: Bite by a rabid dog

Incubation period: 10 days to 1-3 months depending upon the distance of bite from Central Nervous System (CNS), that is the brain or spinal cord.


  1. Severe headache and high fever.
  2. Painful contraction of muscles of throat and chest.
  3. Choking and fear of water leading to death.

Prevention and cure

  1. Compulsory immunization of dogs.
  2. Killing of rabid animals.
  3. Anti-rabies injections or oral doses are given to the person bitten by a rabid animal.

5. Hepatitis

Pathogen: Hepatitis B virus

Mode of transmission: Mainly through contaminated water

Incubation period: 15-160 days


  1. Body ache.
  2. Loss of appetite and nausea.
  3. Eyes and skin become yellowish, urine deep yellow in colour (due to bile pigments).
  4. Enlarged liver.

Prevention and cure

  1. Hepatitis B vaccine is now available in India.
  2. Proper hygiene is to be observed.
  3. Avoid taking fat rich substances.

6. Influenza

Influenza, commonly known as flu is an illness caused by viruses that infect the respiratory tract. Compared to common cold, influenza is a more severe illness.


Influenza is caused by a virus which attacks our body’s cells, resulting in various effects depending on the strain of the virus. There are many strains of influenza virus. The virus mutates all the time and new variations (strains) arise. This constant changing enables the virus to evade the immune system of its host.

A person infected with influenza virus develops antibodies against that virus; as the virus changes, the antibodies against the virus do not recognize the changed virus, and influenza can recur, caused by the changed or mutated virus.


  1. fever (Usually 100° F to 103° F in adults and often even higher in children).
  2. respiratory tract infection symptoms such as, cough, sore throat, running nose, headache, pain in the muscles, and extreme fatigue.

Although nausea, vomiting and diarrhoea can sometimes accompany Influenza infection, especially in children, gastrointestinal symptoms are rarely prominent. Most people who get flu, recover completely in 1 to 2 weeks, but some people develop serious and potentially life-threatening complications, such as pneumonia.

Treatment and Control

  1. Much of the illness and death caused by influenza can be prevented by annual influenza vaccination. Influenza vaccine is specifically recommended for those who are at high risk for complications with chronic diseases of the heart, lungs or kidneys, diabetes, or severe forms of anaemia.
  2. The persons suffering from influenza should
    • drink plenty of fluids
    • take symptom relief with paracetamol, aspirin (not in children under the age of 16) or ibuprofen as recommended by the doctor.
    • Consult doctor immediately for treatment.

7. Dengue

Dengue is an acute fever caused by virus. It is of two types:

  1. Dengue fever is characterized by an onset of sudden high fever, severe headache, pain behind the eyes and in the muscles and joints.
  2. Dengue hemorrhagic fever is an acute infectious viral disease. It is an advanced stage of dengue fever. It is characterized by fever during the initial phase and other symptoms like headache, pain in the eye, joint pain and muscle pain, followed by signs of bleeding, red tiny spots on the skin, and bleeding from nose and gums.

How does Dengue spread?

Dengue spreads through the bite of an infected Aedes aegypti mosquito. The transmission of the disease occurs when a mosquito bites an infected person and subsequently bites a healthy person. In doing so, it transmits blood containing the virus to the healthy person and the person becomes infected with dengue.

The first symptoms of the disease occur about 5 to 7 days after the infected bite. Aedes mosquito rests indoors, in closets and other dark places, and is active during day time. Outside, it rests where it is cool and shaded. The female mosquito lays her eggs in stagnant water containers such as coolers, tyres, empty buckets, in and around homes, and other areas in towns or villages. These eggs become adults in
about 10 days.

Incubation period

The time between the bite of a mosquito carrying dengue virus and the start of symptoms averages 4 to 6 days, with a range of 3 to 14 days.


Diagnosis is made through blood tests by scanning for antibodies against dengue viruses. In addition the blood platelet counts also get drastically reduced in the infected person.

Symptoms of Dengue fever

  1. Sudden onset of high fever, generally 104-105 °F (40 °C), which may last 4-5 days.
  2. Severe headache mostly in the forehead.
  3. Pain in the joints and muscles, body aches.
  4. Pain behind the eyes which worsens with eye movement.
  5. Nausea or vomiting.

Symptoms of Dengue hemorrhagic fever

These include symptoms similar to dengue fever, and other symptoms such as:

  1. Severe and continuous pain in the abdomen.
  2. Rashes on the skin.
  3. Bleeding from the nose, mouth, or in the internal organs.
  4. Frequent vomiting with or without blood.
  5. Black stools due to internal bleeding.
  6. Excessive thirst (dry mouth).
  7. Pale, cold skin, weakness.


  1. Avoid water stagnation for more than 72 hours so that the mosquitoes do not breed there.
  2. Prevent mosquito breeding in stored water bodies, like ponds, and wells.
  3. Destroy discarded objects like old tyres and bottles, as they collect and store rain water.
  4. Use mosquito repellents and wear long sleeved clothes to curtail exposure.
  5. Use mosquito nets, also during daytime.
  6. Avoid outdoor activities during dawn or dusk when these mosquitoes are most active.
  7. Patients suffering from dengue fever must be isolated for at least 5 days.
  8. Report to the nearest health centre for any suspected case of Dengue fever.

Treatment for dengue and dengue hemorrhagic fever

There is no specific treatment for dengue fever. Persons with dengue fever should rest and drink plenty of fluids. Dengue hemorrhagic fever is treated by replacing lost fluids. Some patients need blood transfusions to control bleeding.