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Pathogenesis and Epidemiology
Transmitted by direct contact.
Invades skin locally producing skin vesicles by its cytolytic
Remains latent in the sensory ganglia.
Reactivation is triggered by physical factors (e.g. infection, sunlight),
or psychological stress.
Cell-mediated immunity controls infection, therefore immunocompromised
patients are at risk of reactivation and severe
- Herpes simplex virus 1 (HSV-1) is often asymptomatic, but
young children commonly develop fever, vesicular gingivostomatitis
- Adults with infection may exhibit pharyngitis and tonsillitis.
- Primary eye infection produces severe keratoconjunctivitis;
recurrent infection may result in corneal scarring.
- Primary skin infection (herpetic whitlow) usually occurs in traumatized
skin (e.g. on fingers).
- Severe encephalitis may occur (see Infections of the central nervous system
- Mother-to-child transmission perinatally may result in a generalized
neonatal infection including encephalitis.
- HSV-2 infection causes painful genital ulceration that lasts up
to 3 weeks and is associated with recurrence.
- Genital herpes is an important cofactor in the transmission of
- Meningitis is an uncommon complication of primary type 2
A nucleic acid amplification test (NAAT) of vesicle fluid, genital
or mouth swabs is the standard diagnostic method, although the
virus grows readily and can be visualized by electron microscopy
(EM). The ratio between serum and CSF antibody may indicate
local production and can help in the diagnosis of HSV encephalitis.
MRI or CT scans of the brain may detect temporal lobe lesions
that are typical of herpes encephalitis.
Topical, oral and intravenous preparations of aciclovir and other
agents with better oral absorption, including valaciclovir and famciclovir,
are available. Encephalitis is treated with intravenous aciclovir.
Varicella zoster virus
virus (VZV), which has only one serological type,
causes the acute primary infection known as chickenpox and its
recurrence, which is called shingles.
Pathogenesis and Epidemiology
- VZV is found in the vesicle and transmission is by contact and
airborne spread from patients with vesicles.
- The attack rate in non-immune individuals is very high (>90%).
- The incubation period is 14-21 days.
- Infection is commonest in children aged 4-10 years.
- Recovery provides lifelong immunity.
- The virus remains latent in the posterior root ganglion and in
20% of patients will reactivate with lesions in the related dermatome,
- Shingles lesions contain VZV and are infectious to non-immune
individuals who are at risk of developing chickenpox.
- It is impossible to contract shingles directly from chickenpox or
other cases of shingles.
- The discomfort of chickenpox comes from the rash.
- Systemic symptoms are mild.
- Lesions, which appear in crops usually 2 or 3 days apart, affect
all parts of the body, including the oropharynx and genitourinary
tract, and progress through macules and papules to vesicular eruptions
which, following rupture, develop a crust and spontaneously
- The rash lasts for 7-10 days, but complete resolution may take
as long again.
- Haemorrhagic skin lesions that can be life-threatening may
- Secondary infection with Staphylococcus aureus or Streptococcus pyogenes may also require treatment.
- VZV pneumonia is more common in adults, especially in immunocompromised
individuals, and has a high mortality; survivors
may recover completely or may have respiratory impairment.
- Postinfectious encephalitis, which is usually minor, can occur,
but there is also a rare fatal form.
- Maternal transmission through contact with vaginal lesions
during birth can result in severe neonatal infection.
- Shingles is a painful condition that usually affects older people
or immunocompromised individuals.
- Ocular damage may follow the involvement of the ophthalmic
division of the trigeminal nerve.
- Up to 10% of shingles episodes will be followed by Postherpetic
neuralgia, a very painful condition that may last for many years
and can be associated with suicide.
Treatment and Prevention
- Both chickenpox and shingles are usually diagnosed clinically.
- Laboratory diagnosis is by NAAT.
- Staining of fluid from a vesicle may show characteristic giant
- VZV may be visualized by EM or cultured.
- Serology is important to determine the immune status of patients
and staff in outbreaks.
- Aciclovir or valaciclovir may be used for both adult chickenpox
- Postherpetic neuralgia may be reduced by early treatment.
- Pain may be severe and require referral to a pain clinic.
- A live attenuated-virus vaccine is available and recommended
for non-immune healthcare workers.
- Zoster immune globulin (ZIG) is given to those in close contact
with infection who are at risk of serious disease (e.g. neonates,
pregnant women and immunocompromised individuals).