"INTERNAL MEDICINE": VIRAL INFECTIONS

VIRAL INFECTIONS

HERPES VIRUS GROUP

• Large DNA virus (180-250 nm)

• Intra-nuclear replication producing intra nuclear inclusions

• Absence of virus elimination following clinical recovery

HERPES VIRUSES

8 MEMBERS

• Herpes simplex virus type 1

• Herpes simplex virus type 2

• Varicella zoster virus

• Human cytomegalovirus (CMV)

• Epstein-Barr virus (EBV)

• Human herpes virus 6

• Human herpes virus 7

• Human herpes virus 8

HERPES SIMPLEX

• One of the commonest infections of humans worldwide

• HSV 1 is classically associated with facial infections

• HSV 2 is typically genital

• TRANSMISSION: Direct contact or droplets from infected secretions

• Transmission Rate: 4-30% annually for genital herpes

• Persistence of virus in sensory nerve ganglia after primary infection

• Peripheral travel of virus along the nerve fibre - > Replication in skin & mucous membrane - > Recurrent disease

PRIMARY INFECTION

PRIMARY HSV 1 INFECTION

• Sub clinical often

• Rarely produces a painful vesicular stomatitis

PRIMARY HSV 2 INFECTION

• More commonly symptomatic

HERPETIC GINGIVOSTOMATITIS

• Most common clinical manifestation of primary infection by HSV 1

• Most commonly seen in children between 1-5 years of age

• Incubation period: 5 days

• Symptoms: Constitutional symptoms - fever, malaise, restlessness, excessive dribbling of saliva

• Vesicles & erosions present on the tongue, pharynx, palate & buccal mucosa

• Regional lymph nodes can be enlarged

• Recovery in 2 weeks

• Primary herpetic gingivo-stomatitis in a child

HERPES GENITALIS

• It is a sexually transmitted disease

• Most commonly due to HSV 2

• There are painful papulo-vesicular confluent lesions on the glans, prepuce & shaft of penis

• Lasts for 2-3 weeks, if untreated

• HIV infected individuals – Chronic ulceration

• Females: similar lesions on external genitalia & mucosae of vulva, vagina & cervix

• RECURRENCE: 2/3 of cases have recurrences 2-6/year

HERPETIC KERATOCONJUNCTIVITIS

• Severe purulent conjuctivitis

• Superficial ulceration of the cornea

• May be vesicles on the surrounding skin

RECURRENT INFECTON

• Seen in:

• 30-50% cases of oral herpes

• 50-90% cases of genital herpes

Triggering factors:

• minor trauma

• febrile illnesses

• surgical procedures

• dermabrasion

Asymptomatic shedding of HSV 2 is more frequent than HSV 1

COMPLICATIONS

• Headache & meningism

• Disseminated or systemic infection

• Encephalitis

• Hepatitis

• Pneumonia

• Radiculopathy

• Eczema herpeticum

• Erythema multiforme

• Bell’s Palsy

• Eczema herpeticum

ERYTHEMA MULTIFORME

DIAGNOSIS

• Tzanck smear

• Serology

• Culture

• PCR

• Electron microscopy

TREATMENT

• Mild uncomplicated herpes simplex: no treatment

• Acyclovir: 200 mg 5 times daily for 5 or more days 5 mg/kg i.v. 8 hrly

VARICELLA (CHICKEN POX)

• Transmitted by droplet infection from naso-pharynx

• Vesicle fluid contains large amount of virus

• Dry scabs are not infectious

• Maternal varicella occurring first 20 weeks of pregnancy 2% risk of fetal damage central nervous system and ocular defects, and limb hypoplasia; neonatal death

• Maternal zoster in pregnancy is not associated with intrauterine infection

• Mothers having varicella within 4 days before to 2 days after term neonate at risk of severe varicella with a mortality rate up to 30% in the absence of treatment

CLINICAL FEATURES

• Incubation period: 14-17 days

• Symptoms: Fever and malaise 1-2 days

• Development of papules rapidly becoming tense, clear, turbid then pustular

• Vesicles appear in crops hence polymorphic lesions

• Distribution is centripetal most numerous on the trunk, then on the face and scalp and on the limbs.

• Mucous membranes: Vesicles in the mouth, palate, including the conjunctiva & on anal mucosa they may be followed by painful ulcers.

COMPLICATIONS

• Encephalitis

• Secondary infection (Varicella gangrenosa)

• Pneumonia: most common cause of mortality

• Thrombocytopenic purpura

• Hepatitis

• Rhabdomyolysis

• Varicella arthritis

• Steven Johnsons syndrome

HERPES ZOSTER

Reactivation of virus within the posterior root ganglia of the spinal cord or within the cranial nerve root ganglia

SYMPTOMS:

• Pain may be accompanied by fever, headache, malaise and tenderness localized to areas of one or more dorsal roots.

• Closely grouped red papules, rapidly becoming vesicular and then pustular, develop in a continuous or interrupted band in the area of one, or occasionally two contiguous dermatomes.

RECOVERY:

• Uncomplicated cases in 2-3 weeks in children and young adults, and 3-4 weeks in older patients.

• Post-herpetic neuralgia: defined as persistence or recurrence of pain more than a month after the onset of zoster

TREATMENT

• Only symptomatic treatment in otherwise healthy children for chicken pox

• Secondary bacterial infection will require antibiotics

• Antiviral for severe varicella or zoster infections at any age in the immunocompromised

• Aciclovir : 800 mg 5 times a day – 1 week

• Post-herpetic neuralgia: Pain killers, but opiates should be avoided

• Amitriptyline or clomipramine or doxepin

PREVENTION

• Pre-exposure: A live attenuated vaccine two doses of vaccine, 3 months apart

• Post-exposure: Specific zoster immune globulin (ZIG) administered within 10 days of contact given to neonates whose mothers develop varicella within the period from 7 days before to 7 days after delivery

Posted by Unknown Saturday, September 26, 2009