3. • Varicella-zoster virus (VZV) is a DNA virus
of the herpes virus family.
•It causes two diseases:
•varicella (chickenpox), the primary infection,
•and herpes zoster (shingles), a secondary
infection due to a reactivation of latent varicella
infection in the dorsal root ganglia
Infectious agent
4. Signs and Symptoms
• Symptoms include a skin rash of blister-like lesions,
covering the body but mostly concentrated in the face,
scalp and trunk. Most infected individuals experience
fever developing either just before or when the rash
appears. If a vaccinated individual is exposed they may
experience a milder illness with less severe rash and mild
or no fever.
dewdrops on a rose petal
5.
6. Occurrence
• Worldwide.
• At lease 90% of the population has had chickenpox by age 15
• At lease 95% by young adulthood
• In temperate zones, chickenpox occurs most frequently in winter
and early spring.
• The epidemiology of varicella in tropical countries differs from
temperate climates, with a higher proportion of cases occurring
among adults.
• Herpes zoster occurrence has been described most commonly in
developed countries where Zoster occurs more commonly in
older people 50 years of age.
7. Occurrence
• Chickenpox typically infects children under the age of 10;
5-10 % of the population remains susceptible to the
disease in adulthood.
• Lifetime risk of reactivation as zoster/shingles is about 15-
20 % and can occur at any time, most often in the elderly
population.
9. Mode of transmission
•Person-to-person by direct contact,
•Droplet or airborne spread of vesicle fluid,
•Secretion of the respiratory tract of chickenpox cases
•Vesicle fluid of patients with herpes zoster
•Indirectly through articles freshly soiled by discharges
from vesicle and mucous membranes of infected
people
10. Mode of transmission (cont.)
•Varicella in unvaccinated persons is one of the
most readily communicable of diseases,
especially in the early stages of the eruption,
•Secondary attack rates in susceptible household
contacts range from 61% to 100%
•Scabs from varicella lesion are not infective.
11. Mode of transmission (cont.)
•Herpes zoster has a lower rate of transmission:
•Data from a household study showed that 20%
of those who are varicella seronegative develop
varicella when they are in contact with persons
who have herpes zoster
12. Incubation period
•10-21 days
•Commonly 14-16 days
•May be prolonged as long as 28 days after passive
immunization against varicella
•And may be shortened in the immunodeficient.
(8-21 days)
13. Period of communicability
•As long as 5 days,
•But usually 1-2 days before onset of rash,
•And continuing until all lesions are crusted
(usually about 5 days).
14. Period of communicability (cont.)
•Contagiousness may be prolonged in patients
with altered immunity.
•The secondary attack rate among susceptible
siblings is 60-100%.
•Patients with herpes zoster may be infectious for
a week after the appearance of vesiculopustula
lesion.
•Susceptible individuals should be considered
infectious for 10-21 days following exposure.
16. Susceptibility
•Susceptibility to varicella is universal among
those not previously infected or vaccinated;
• Ordinarily a more severe disease of adults than of
children.
•Infection usually confers long immunity;
• Second attack are rate in immunocompetient persons
but have been documented ;
• Subclinical reinfection is common.
17. Susceptibility
•Viral infection remains latent;
• Disease may recur years later as herpes zoster.
•Herpes zoster occurs in about 15% of older adults,
and rearly in children.
18. Susceptibility
•Neanates whose mothers are not immune and
patients with leukemia may suffer severe,
• Prolonged or fetal chickenpox.
•Adults with cancer-especially of lymphoid tissue,
with or without steroid therapy-immunodeficint
patients and those on immunosuppressive
therapy may have an increased frequency of
severe herpes zoster, both localized and
dissaminated.
19. Methods of control
•Preventive measures.
•Control of patient, contacts and the immediate
environment.
•Epidemic measures.
20. Methods of control ; Preventive measures
•Protect high-risk individuals who cannot be
immunized
• e.g. non-immune neonates and the immunodeficient-
from exposure, by immunizing household or other
close contacts.
21. Methods of control ; Preventive measures
•A herpes zoster vaccine
• for older adults has been approved and recommended for
use in the USA for healthy persons aged 60 years or older.
•Varicella-zoster immune globulin (VZIG orVariZIG),
• prepared from the plasma of noemal blood donors with
highVZV antibody titer,
• effectively modifies or prevents disease if given within
96 hours after exposure.
22. Methods of control ;Control of patient, contacts
and the immediate environment.
• Isolation
• Exclude children from school, medical offices, emergency
rooms or public places until vesicles become dry and
crusted, usually after 5 days in non-immunized children
and 1-4 days with breakthrough varicella in immunized
children;
• Exclude infected adults from workplace and avoid contact
with susceptibles.
•In hospital, observe strict isolation, because
of the risk of varicella in susceptible
immunocompromised patients.
23. Methods of control ;Control of patient, contacts
and the immediate environment. (cont.)
•Quarantine.
• in places where susceptible children with known
recent exposure must remain for medicle reasons, the
risk of spread to steroid-treated or immunodeficient
patients may justify quarantine of known contacts for
at lease 10-21 days after exposure (up to 28 days if
VZIG was given).
24. •Protection of contacts:
• Varicella vaccine is effective in preventing illness or
modifying severity if used within 3 days, and possibly
up to 5 days, of exposure; it is recommended for
susceptible persons following exposure to
varicella.
Methods of control ;Control of patient, contacts
and the immediate environment. (cont.)
25. •Protection of contacts: (cont.)
• VZIG
• Within 96 hours of exposure may prevent or modify
disease in susceptible close contacts of cases.
• It is available in several countries for high-risk persons
exposed to chickenpox, and indicated for newborns of
mothers who develop chickenpox within 5 days prior to
or 2 days after delivery.
• There is no assurance that administeringVZIG to a
pregnant woman will prevent congenital malformations
in the fetus, but it may modifify varicella severity in the
pregnant woman.
Methods of control ; Control of patient, contacts
and the immediate environment. (cont.)
26. •Protection of contacts: (cont.)
• Antiviral drugs such as acyclovir
• appear useful in preventing or modifying varicella in
exposed in individuals if given within a week of
exposure. Most studied have been carried out in
immunocompromised children, with few data available
for healthy children.
• A dose of 8o mg/kg/day in 4 divided doses has been
used,
• But no regimen is as yet generally recommended for this
purpose.
Methods of control ; Control of patient, contacts
and the immediate environment. (cont.)
27. Methods of control ; Control of patient, contacts
and the immediate environment. (cont.)
•Specific treatment:
• Antiviral therapy is moderately effective in treating
varicella and herpes zoster infections: acyclovir,
valacyclovir or famcyclovir are considered the agents
of choice for treatment or varicella…
