Human Herpesvirus Flashcards
What is the difference between HSV-1 and HSV-2?
Infections are indistinguishable, but at the DNA level they have a difference of 50% sequence homology.
HSV biology
HSV-1 and HSV-2 primarily infect epithelial (mucoepithelial) cells wherein they can initiate DNA replication.
HSV epidemiology
Worldwide distribution. Humans are the natural reservoir HSV-1 infection usually acquired during first 5 years of life, 80-90% of adults have antibodies Antibodies to HSV-2 usually appear during puberty. Rates of infection dependent on sexual habits, and gender (higher in women than men).
HSV transmission
Close contact with person shedding virus from skin, mucosal surface, or in genital and oral secretions (saliva). HSV-1 usually spread by oral contact. HSV-2 usually spread via sexual contact.
HSV clinical manifestations (primary infection)
Orofacial infections (gingivostomatitis and pharyngitis).
- Common in first episode of HSV-1 infections, infection in toddlers/children between 1 and 5 years and young adults.
- Symptoms and signs (generally after 2-5 days incubation) include:
- fever, malaise, myalgias, cervical lymphadenopathy,
- white lesions (ulcers) on lips, hard and soft palate, gingivia, tongue, posterior pharynx, and tonsillar pillars
- Fever subsides in 3-5 days; oral pain and lesions usually cleared in 2-3 weeks
- Autoinoculation can also result in transfer or (secondary) infection elsewhere in the body (i.e. herpetic whitlow)
How do HSV recurrent infections occur?
HSV’s can infect neuronal cells and remain dormant in the nucleus; virus expresses only latency-associated genes but does not replicate. In response to various stimuli (ie. stress, trauma, fever etc.) the virus will initiate replication, and can travel to the initial site of infection.
Recurrences average 2-3 episodes a year. Oral HSV-1 infections recur more often than oral HSV-2 infections. Lesions can appear anywhere in the oral cavity/oropharync or on the face but usually recur on the lips (cold sores). Usually a prodromal tingling/itchin and/or pain precedes the appearance of lesions.
HSV genital infections
After 2-5 days of incubaion, primary infection moderately severe of around 3 weeks duration.
Symptoms and signs often include:
- Fever, general malaise and pain
- Dysuria (i.e. pain on urination)
- Widespread ulceration
- Inguinal lymphadenopathy
Appearance of lesions in men:
- Lesions (clear vesicles) develop on the glans or shaft of the penis (rarely in the urethra)
- Anal/perianal lesions most common is MSM (but increasingly being seen in heterosexual men)
Appearance of lesions in females:
- Lesions appearance associated with itching and vaginal discharge
- Lesions appear on the vulva, vagina, cervix, perianal area/or inner thigh
HSV recurrent genital herpes
- Reactivation of latent HSV in the sacral ganglion.
- More likely to recur if caused by HSV-2 than HSV-1
- Usually also preceded by tenderness, itching, burning, pain
- Generally less lesions and less severe than primary infection
- Recurrence can be every 2-3 weeks (or infrequent)
Complications of HSV
HSV Encephalitis
- Caused by HSV-1 (adults) and HSV-2 (neonatal), with viral invasion o fthe brain; generally localised to one of the temporal lobes.
HSV meningitis
- Complication of genital HSV-2 infections
HSV keratitis
- Usually associated with HSV-1, affecting the cornea, causing pain, redness, blurred vision, tearing, discharge, sensitivity to light and even blindness if cornea severely scarred.
Neonatal infections
- 70% of infections are HSV-2
- Occurs after birth (infected mother with asymptomatic shedding of virus)
- Disease localised to skin, eyes and mouth, or disseminated (liver, lungs, and CNS involvemnt)
- Prevention via caesarian birth or antiviral therapy at time of delivery
Eczema herpeticum
Herpes gladiatorum
Oesophagitis
Hepatitis
Myelitis
Varicella-Zoster virus epidemiology
Varicella (chickenpox) infection
- Comon worldwide
- Usually acquired in childhood by 4-10 years of age
- By adulthood, 90% of tthe population usually have antibodies to VZV
Herpes zoster (shingles)
- 10-20% of people previously infected by varicella are likely to develop shingles
- Shingles lesions contain viable virus, which can be a source of varicella infection for non-immune children.
- Reactivation is dependet on age and immune status of host.
- Higher rates of reactivation for people >50-60 years of age
- People with declining T-cell immunity and/or suppression (ie people with lymphoma; leukaemia; multiple myeloma; HIV/AIDS)
VZV transmission
High contagious because spread via:
- Respiratory droplets from the nose, mouse, and throat of infected people
- Skin lesions
- Infected people are a source of virus just before and during symtpoms
VZV manifestations
Viricells (chickenpox)
- For immuncompletent children, primary infection is usually mild and symptomatic
- After 13-15 (range 7-23 days) incubation period, symptoms and signs include:
- Fever, malaise, headache, and abdoominal pain
- Characteristic maculopapular rash (over entire body, mucous membranes and scalp) formed in hours and can crust over in 3-7 days
- Rash often displays variable lesion presentation
- Macules
- Papules
- Vesicles
VZV potential complications
Secondary bacterial infection (Step and staph)
Viral pneumonia
- Serious for immunocompromised; adults; pregnant women
- Shortness of breath, and cough, 2-3 days after onset of rash
- Complete recovery, fibrosis of the lung(s); or death
Haemorrhagic chickenpox
- Bleeding into skin lesions, mucous membranes and unaffected skin
- Associated with thrombocytopenia (reduction in platelets)
Encephalitis
- In children
- Headaches
- Nausea
- Vomiting
- Nystagmus
- Ataxia
- Self-limited
- In adults
- Altered senses (touch, perception, cognition, for example)
- Seizures and focal neurological abnormalities
- Mortality rate approx. 35%
Reyes syndrome
- Encephalitis associated with hepatitis (liver injury)
- Aspirin and other salicylate-containing compounds SHOULD be AVOIDED when treating pain and fever associated with VZV infection
- Fatality rate approx. 20%
What are the clinical complications of HSV for pregnant women?
- Virus can cross the placenta causing congenital varicella associated with skin scarring; limb hypoplasia; ocular and brain abnormalities
- Seen in 1% of pregnancies if varicella infection occurs during 13-20 weeks of gestation
- Neonatal chickenpox: if mother infected late in pregnancy; not enough time to transfer sufficient IgG-anti-VZV antibody; associated with 30% mortality
Clinical manifestations of herpes zoster
- Presentation is generally dependent upon which dermatome is carrying the reactivated virus
- Appearance of rash preceded by burning pain and tenderness at site of eruption
- Rash similar to chickenpox evolving through papular, vesicular and crusting stages
- Pain is self-limited BUT up to 30% of patient (>50 yoa) experience a postherpetic neuralgia (pain that lasts >3 months to years after lesions have already cleared from the infected area)
