dispersion of droplets of respiratory secretions in the surrounding air. It can also spread by direct contact with the chickenpox or herpes lesions as these contain infectious fluid.

Chickenpox is contagious from two days prior to appearance of the rash till all the lesions are covered by a scab, which occurs usually by 4-5 days of the rash. However, the transmission is most likely within first two days before the appearance of the rash.

Chickenpox is a highly contagious disease. Following a case of chickenpox, upto 90% of susceptible children and adults who come in close contact with the case can develop infection. Therefore, when one child develops chickenpox, many susceptible children in the school and persons in the child's house develop the disease.

Isolating the infected child and avoiding contact with him can prevent spread of infection. However, chickenpox is most infectious before the rash develops when there is no reason to suspect that he has chickenpox. Such a child, during this period, may continue to attend school, play with his playmates and therefore spread the disease.

Once a child has come in contact with a case of chickenpox, he can be immunized with antibodies (varicella zoster immunoglobulin) against the virus. However, for the immunization to be effective, it has to be given within 3-4 days of exposure. It is costly and offers protection only for a few weeks.Vaccination against chickenpox is now available and offers long-term protection against the disease.

Many people contract chickenpox during childhood or adolescence, but adults who have not been infected before are susceptible to infection and can develop chickenpox in adulthood if and when they come in contact with a case.

Chickenpox presents with a characteristic rash. The rash first appears over the face, scalp or trunk. The rash initially consists of red / purple colored raised lesions (maculo-papular rash) which evolve into lesions filled with clear fluid. These lesions are called vesicular lesions. The fluid in these lesions then becomes hazy given the rash a characteristic blistered or pustular appearance. Most children have 200-300 lesions, which appear in successive crops and hence at a given time different types of lesions are present. The lesions then form a crust after 4-5 days of appearance. The crusts fall off after a week or two.

The rash is itchy and a young infant may get irritated due to the constant itch. Other common symptoms include fever, nausea and anorexia, bodyache, vomiting, listlessness, etc.