25. Viral Infections

Question 1

What is the most common cause of oral viral infection in humans?

Answer 1

human herpesviruses

Question 2

Properties of human herpesviruses

Answer 2

• all structurally similar
• enveloped
• icosahedral
• 180-200nm in diameter
• double-stranded DNA - linear DNA
• inactivated by solvents like alcohol and common disinfectants
• neurotropic
• latent - can re-infect host and cause recurrent infection

Question 3

How do human herpesvirus get into human cells?

Answer 3

• nucleocapsid transported to host cell nucleus
• viral DNA uncoated
• 3 classes of mRNA are produced - immediate early, delayed early and late
• translation of early and then late proteins
• viral nucleocapsids assembled in nucleus
• viral envelope added during budding through nuclear membrane as exit nucleus

Question 4

Pathogenesis of herpesvirus infections

Answer 4

• herpesviruses can remain latent in the body after initial infection
• reactivate under conditions of stress or when immune system is compromised
• herpesviruses can infect neuronal cells and travel to nerve ganglia
• replicate in ganglia or establish a latent infection
• reactivation via certain triggers
• virus travels along neurones and develops secondary infection in relevant dermatomes

Question 5

Types of human herpesviruses

Answer 5

• human herpesvirus 1 (HHV-1)
• herpes simplex virus (HSV-1)
• HHV-2
• herpes simplex virus 2 (HSV-2)
• HHV-3
• varicella-zoster virus (VZV)
• HHV-4
• Epstein-Barr Virus (EBV)
• HHV-5
• Human Cytomegalovirus

Question 6

Herpes simplex is caused by …
Primary infections is acquired through …

Answer 6

• HSV 1 and 2/human herpes viruses 1 and 2
• direct contact or contaminated secretions

Question 7

Primary Herpes simplex infections

Answer 7

• primary gingivostomatitis
• herpetic whitlow
• genital herpes
• conjunctivitis
• encephalitis

Question 8

Explain herpes simplex 1

Answer 8

• common
• given through direct contact with infected lesions or saliva
• 3-5 day incubation
• 2-3 week long lesions
• typically infects epithelial cells around mouth
• oral and pharyngeal ulceration

Question 9

Explain herpes simplex 2

Answer 9

• one of the most common sexually transmitted diseases
• HSV-2 infections associated with anogenital area
• most likely to be spread if current, active lesions but also transmitted in asymptomatic periods

Question 10

Symptoms in a herpes simplex primary infection

Answer 10

• prodomal symptoms like burning, itching, tingling in skin or mucosa for a day or so
• systemic symptoms like fever, malaise, nausea, vomiting, accompanying lymphadenopathy

Question 11

Explain transmission and symptoms of primary herpetic gingivostomatitis

Answer 11

• common in young children
• via direct contact with infected lesions or saliva of person with infected lesion
• oral lesions around lip, mouth, less so on tongue, face, palatal/buccal mucosa
• blisters/vesicle erupt as clusters and ooze clear-yellowish fluid that can develop into yellow crust
• ulcers cause intense erythema in gingiva and bleeding
• painful oral ulceration
• pyrexia and increased salivation

Question 12

Treatment of primary herpetic gingivostomatitis

Answer 12

• treat symptoms with anti-pyretic medication, rest and maintain fluid intake
• wait for infection to run it’s course (1-2 weeks)

Question 13

Explain herpetic whitlow

Answer 13

• herpes simplex infection in fingers
• caused by inoculation from another infected site
• infection of fingers acquired by dentists and nurses due to contamination of hands in viral laced saliva or secretions

Question 14

How can facial herpes infection become recurrent?

Answer 14

• reactivation of latent virus at trigeminal ganglion

Question 15

Explain herpes labialis

Answer 15

• cold sores
• most common manifestation of recurrent herpes simplex virus infection
• lesions appear at mucocutaneous junction of lip
• fluid-filled semi-translucent blisters which enlarge and coalesce to form large blister that weeps exudate
• typically after 2-3 days lesions rupture and crust over
• can last up to 12 days
• infectious virus shed from lesion until healed

Question 16

Triggering factors that cause reactivation of herpes labialis include …

Answer 16

• other illness like common cold
• emotional stress
• exposure to cold/sunlight/UV
• menstruation
• dental treatment
• immunosuppresion

Question 17

Symptoms of herpes labialis

Answer 17

• lesions in mucocutaneous junction of lip
• prodomal paraesthesia/burning/tingling at site of future blisters

Question 18

Management of herpes labialis

Answer 18

• adequate hydration, pain, fever management
• with analgesics and antipyretics and topical anesthetics such as lidocaine gel
• antiviral medication (acyclovir)
• reduce symptoms if started within 24-48 hrs of vesicle eruption, recurrent infections treated symptomatically, severe cases need systemic antiviral medication

Question 19

What is human herpes virus 3 - VZV?

Answer 19

• causes chicken pox and shingles
• pox is the primary and shinges the reactivation

Question 20

Explain chicken pox

Answer 20

• highly contagious
• benign infection in childhood and self limiting
• transmission by direct contact with infected or by droplets/nasopharyngeal secretions
• incubation of 10-21 days

Question 21

How does chickenpox infect the body?

Answer 21

• enters epidermal cells
• and via retrogade axonal transport to neuronal cell bodies in sensory doral root ganglia
• becomes latent there

Question 22

Symptoms of chickenpox

Answer 22

• fever, malasie, sore throat
• intense, uncomfortable, itchy rash on trunk and face
• rash becomes vesicles before scabbing over
• worse in adulthood/pregnancy
• can be oral lesions on palate, buccal mucosa and uvulu

Question 23

How to manage chickenpox?

Answer 23

• symptomatic relief
• adequate hydration, rest, fever control by paracetamol, lotion for rash
• severe infections may require antiviral therapy

Question 24

Herpes zoster is what?
How does it cocur?

Answer 24

• reactivation of Varicella-zoster virus infection/chicken pox
• more common in elderly
• predisposed with age, immunosuppression, stress/trauma

Question 25

Initial clinical signs of Herpes Zoster

Answer 25

• unilateral pain in dermatome supplied by nerve in which virus has become latent
• headache, photophobia and malaise

Question 26

Clinical symptoms of Herpes Zoster

Answer 26

• severe neuralgic burning pain
• development of rash in dermatome
• clusters of clear vesicles
• these rupture, ulcerate and crust over in 7-10 days
• fever and malaise
• pain continues until legions heal
• can have long term neuralgic pain/numbness

Question 27

Herpes zoster of the trigeminal area

Answer 27

• pain precedes rash
• lesions localised to one side - within distribution of any divisions of trigeminal nerve
• malaise and pain are severe, life-threatening in immunosuppression
• patients may require treatment with systemic antiviral drugs like acyclovir
• antibiotics may be required if rash/vesicles become infected

Question 28

Dental considerations of herpes zoster

Answer 28

• oral manifestations like intra-oral vesiclesm ulceration, localised/unilateral
• unilateral pain and ulcers in trigeminal herpes zoster

Question 29

Management of herpes zoster

Answer 29

• analgesia
• antiviral medication (acyclovir)

Question 30

Human herpes virus 4/EBV causes what?

Answer 30

• infectious mononucleosis (glandular fever)
• Burkitt’s lymphoma
• oral hairy leukoplakia

Question 31

What percentage of the world report to be infected with EBV?
Where’s the highest prevalence?

Answer 31

• 90-95%
• in adolescents and young adults

Question 32

Explain infectious mononucleosis

Answer 32

• caused by EBV in 90% of cases or cytomegalovirus
• from kissing infected individuals, infected parents or siblings
• sudden onset sore throat, sloe development of malaise, myalgia, posterior cervical lymphadenopathy, palatal petechiae

Question 33

Explain human herpes virus 5 - human cytomegalovirus

Answer 33

• almost ubiquitous virus causes acute primary disease and remain latent for recurrent infection
• almost all infections are asymptomatic
• can cause infectious mononucleosis-like symptoms