HERPES VIRUSES

HERPES VIRUSES

1. Double stranded enveloped DNA viruses

2. 9 types known to infect humans

3. characterised by their ability to establish latency and reactivate

4. HERPES SIMPLEX 1 + 2

   • Disease names
     • HSV1 = cold sores
     • HSV2 = genital herpes
   • Epidemiology
     • exists worldwide, humans are only known reservoir
     • 80% of UK population experience HSV1 at least once in lifetime
     • 10-20% of the UK population have experienced HSV2
   • Mode of transmission
     • direct skin, genital or eye contact w/ vesicle fluid from HSV lesions
   • Important clinical syndromes
     • Ulcers to skin or mucous membranes, typically mouth (1) and genitals (2)
     • Encephalitis; often sever or fatal, 95% of cases are HSV1
     • Meningitis; usually associated with HSV2 often follow general lesions
     • Neonatal herpes; severe disseminated herpes

5. VARICELLA ZOSTER VIRUS

   • Disease names
     • primary infection is chicken pox
     • reactivation is herpes zoster or shingles
   • Epidemiology
     • in the UK 95% of people have had chicken pox by age 20
     • in the tropics, only 50% of people have had it before 20
   • Mode of transmission
     • resp. droplets from person with the primary infection
     • vesicle fluid from person with primary infection or reactivation
     • after primary infection, latency established in dorsal root ganglia
   • Important clinical syndromes
     • Chicken pox
       • febrile illness with widespread vesicular rash
       • usually uncomplicated
       • complications include:
         • pneumonitis (esp. adults)
         • acute cerebellar ataxia
     • Shingles/Herpes zoster
       • reactivation causing unilateral vesicles in a dermatomal distribution

6. EPSTEIN BARR VIRUS

   • Disease names
     • Glandular fever/Infective mononucleosis
   • Epidemiology
     • 90-95% of the UK are affected by age 25
     • 50% are affected by age 5
   • Mode of transmission
     • virus is shed in saliva and genital secretions ("kissing disease")
   • Important clinical syndromes
     • Infectious mononucleosis
       • sore throat, fever, lymphadenopathy, hepatosplenomegaly
       • atypical lymphocytes on blood film
       • 80-90% of clinical infection mononucleosis is EBV, the rest is cytomegalovirus
     • Reactivation
       • especially if unwell or immunosuppressed - prolonged shed of virus, often asymptomatic

7. CYTOMEGALOVIRUS

   • Important clinical syndromes
     • infectious mononucleosis (primary infection)
     • congenital infection
       • in infants born to mothers having and primary infection during pregnancy
       • retinitis, deafness, microcephaly, hepatospelomegaly in the neonate
     • immunosuppressed transplant recipients
       • primary infection acquired from the transplanted organ/blood product
       • reactivation as a result of immunosuppression
     • patients with advanced HIV/AIDS
       • reactivation of CMV, causing retinitis or colitis