Infectious diseases

1. Infectious diseases

2. Chickenpox is a highly contagious disease, presenting with sudden onset of low grade fever , a centripetal , pleomorphic rash appearing on the first day of illness and relatively short course of illness .

3. Epidemiology • Occurrence : Occurs worldwide in both epidemic and endemic forms • Ecological triad: • Agent: Varicella-Zoster (DNA virus, member of herpes viruses ) • Host: Children under 10 yrs of age (peak incidence between 5 – 9 years ) both sexes are susceptible C. Environment: In temperate climate it is common in winter but in subtropics common in summer, over crowding favors spread

4. Natural history Reservoir: is a case of chickenpox Infective materials: oropharyngealsecretions, lesions of skin and mucosa Infectious period: for about 7days before the appearance of rash and 6 days after first crop of vesicles Mode of transmission: respiratory droplets, direct contact Incubation period: 14 to 16 days .

5. Pathology : - • Macules ----- papules ------vesicles ------ crust • May cause interstitial pneumonia

6. Nature of rashes : - • Chickenpox causes a red, itchy rash on the skin that usually appears first on the abdomen or back and face, and then spreads to almost everywhere else on the body, including the scalp, mouth, nose, ears, and genitals. • The rash begins as multiple small, red bumps that look like pimples or insect bites. They develop into thin-walled blisters filled with clear fluid, which becomes cloudy. The blister wall breaks, leaving open sores, which finally crust over to become dry, brown scabs. • Chickenpox blisters are usually less than a quarter of an inch wide, have a reddish base, and appear in bouts over 2 to 4 days. The rash may be more extensive or severe in kids who have skin disorders such as eczema

7. Clinical features • Prodromal symptoms: Mild Fever (38 to 39 c) Malaise Anorexia • First sign: Appearance of a characteristic rash on trunk 1st day of illness The rashes spread to head and extremities Macule-Papules-Vesicles-Pustules-Crusts • Itching is marked

11. Diagnosis • Clinical: The disease is usually recognized by characteristic clinical signs • Laboratory examinations: Cytology of vesicular fluid or scrapings ( during first 3 days of onset ) ELISA for serological diagnosis Detection of varicella specific antigen in vesicular fluid with immunoflurescence Serology : - Culture of vesicular fluid

12. Prevention and control Preventive measures: • Notification • Isolation in early first week • Disinfection of discharges from nose,throat,skin lesions • Immunization Treatment: • Symptomatic and supportive • Personel hygiene should be optimized • Symptomatic therapy: analgesics,antipyretics,antipruritics • Antiviral therapy for immunocompromised

13. Cont.. Acyclovir ( within 24 hours of onset of rash ) Dose : - 20 mg /kg four times a day for 5 days Foscarnet ( acyclovir resistant cases ) • Local antiseptic: Dettol,Betadine,Savlon etc... • if secondary infections- • Antibiotic therapy:Flucloxacillin • Aspirin is contraindication for the risk of precipitating Reye`s syndrome.

14. complications Viral effects: • Pneumonia • Facial nerve palsy • Cerebellar ataxia • optic neuritis • Hepatitis • ITP ( idiopathic thrombocytopenic purpura ) Secondary bacterial infections: • Septicaemia • Osteomyelitis/septic arthritis • Glumerulonephritis Intrauterine infections: • Congenital limb defects( varicella embryopathy)

15. Vaccination Varicella zoster immune gammaglobulin ( VZIG) : - 215 U / kg ( max. 625 U) The antibodies against varicella have been detected in over 90% of vaccines one year after immunization and immunity persists for beyond 20 years Vaccine should be stored between +2 / +8 degree thus can be stored for 24 months Indications: Immunocompromised children Sero-negative women of child bearing age All susceptible children (12mths- 12 yrs) Health care workers The vaccine is given subcutaneously,usually in the upper arm Doses and schedule: 0.5ml of reconstituted vaccine contains one immunizing dose,13 yrs and above with no h/o disease 2 doses with an interval of 6-10 weeks

16. Adverse effects: Redness at the site of injection (5%) Varicella like rash (3-4%) Contraindications: Pregnant women Acute fever Known hypersensitivity to neomycin Total lymphocyte count < 1200/mm3

17. Reye's syndrome • Reye's syndrome is a potentially fatal disease that causes numerous detrimental effects to many organs, especially the brain and liver. It is associated with aspirin consumption by children with viral diseases such as chickenpox. • The disease causes fatty liver with minimal inflammation, and severe encephalopathy (with swelling of the brain). The liver may become slightly enlarged and firm, and there is a change in the appearance of the kidneys. Early diagnosis is vital, otherwise death or severe brain damage may follow.

18. . • Stage I • Persistent, heavy vomiting • Generalized lethargy • General mental symptoms, e.g. confusion Stage II • Stupor caused by minor brain inflammation • Hyperventilation • Fatty liver (found by biopsy) • Hyperactive reflexes • Stage III • Continuation of Stage I and II symptoms • Possible coma • Possible cerebral edema • Stage IV • Deepening coma • Large pupils with minimal response to light • Minimal but still present hepatic dysfunction • Stage V • Very rapid onset following stage IV • Deep coma • Seizures • Multiple Organ failure [1] • Flaccidity • Extremely high blood ammonia (above 300mg/dL of blood) • Death