I.Varicella
1.symptoms and signs
The incubation period is 7-23 days (mean =2 weeks ). A shortened incubation period can be especially encountered in immunocompromised patients .
In children , the illness begins with the characteristic rash but in adults , a prodrome resembling an influenza-like illness commonly presents a few days earlier .
Neck lymphadenopathy is commonly present. The rash is characteristically centripedal in distribution and is seen mainly in areas not exposed to pressure , such as the flank , shoulder blades , and in the axillae .
The skin lesions progress rapidly through the stages of macules to papules to vasicles which rapidly break down with crust formation .
The lesions appear in a series of crops so that all stages in thier genesis can be seen at any one time. patients with varicella are generally considered to be infectious 2 days before the appearance of the rash and 7 days after onset , when the vesicles have crusted .
2. Complications
a. secondary bacterial infection is by far the most common complication of varicella . Bacterial infection of the skin does not increasew the risk of scarring . Secondary bacterial pneuumonia can occur but is very uncommon .
b. Haemorrhagic chickenpox - Haemorrhagic symptoms sometimes occur during the course of varicella and usually present 2-3 days after the onset of the rash .
Haemorrhage into the skin , epitaxis , malaena or haematuria may be present .
The haemorrhage may be so severe as to be life threatening.
although thrombocytopenia and DIC occur during varicella , nothing is known about the pathogenesis of this serious complication .
c. Viral pneumonia - viral pneumonia is the most serious complication os varicella .
It is mainly seen in immunocompromised individuals but can occur in normal people , particularly adults .
The chest X-ray usually reveals scattered areas of consolidation typical of a viral pneumonia . It may be difficult to distinguish this condition from bacterial pneumonia unless a biopsy is taken .
The disease frequently runs a fulminating course and results in death , especially in immunocompromised individuals .Surviving patiens may recover completely or be left with permanent fibrosis of the lungs .
d. Encephalitis- it is not known how often the CNS is involved in varicella , minor degrees of CNS involvement is probably common as isolated paralysis of occulomotor muscles has often been noted following varicella .
Typical cases of encephalitis that proceed to coma are rarely seen and are certainly less common than the encephalitis associated with measles .
CNS involvement occurs much more frequently in immunocompromised patients.
e. Other complications - other neurological disorders such as meningitis, cerebella ataxia and Guillain-Barre syndrome have been reported .
Reyes syndrome , which consist of an often fatal encephalopathy secondary to liver damage , is linked with several viral infections of which varicella is second on the list after influenza .
Other manifestations that have been reported include arthritis myocarditis, renal and ureteric damage has been reported .