Micro L8

Medical Virology & Mycology

• Instructor: Kamyar Motavaze, Ph.D.

• Institution: Oxford College

Key Terms

• Verrucous carcinoma

• Herpetic whitlow

• Gingivostomatitis

• Glandular fever

• Hairy leukoplakia

• Avian flu

• Koplik’s spots

• Poliomyelitis

• HFM disease

• German measles

• Dermatophytosis

• Thrush

Papovaviruses

• Human Papillomavirus (HPV)

  • Causative agent of skin warts (verrucae), oral squamous papillomas, and verrucous carcinoma.

  • **Infections: **

    • Skin Warts:

      • Benign epithelial tumors transmissible via direct contact.

      • Less common in adults.

      • Anogenital warts caused by specific HPV serotypes, identifiable in cervical biopsies.

    • Oral Squamous Papillomas and Warts:

      • Small, exophytic, pedunculated lesions occurring between ages 30-50 years, more common in men.

    • Verrucous Carcinoma:

      • Associated with HPV-16, 18, and 33 causing cervical cancer.

      • Certain serotypes cause vulvar cancer and lymphoma.

      • Epidermodysplasia verruciformis is a type of malignant wart.

Adenoviruses

• Causative agents of latent infections in lymphoid tissues (e.g., tonsils).

• Infections:

  • Acute Respiratory Disease: influenza-like infection causing pharyngitis and conjunctivitis.

  • Febrile Pharyngoconjunctivitis.

  • Keratoconjunctivitis.

  • Pneumonia.

  • Gastroenteritis.

• Transmission: Via respiratory and ocular secretions (e.g., swimming pools).

Herpesviruses

• Types: 8 different types (HHV-1 to HHV-8).

• Herpes Simplex Virus (HSV) [HHV-1&2]:

  • Infections:

    • Primary Infections:

      • Gingivostomatitis: affects lips/mouth.

      • Genital herpes: mostly HSV-2.

      • Encephalitis.

      • Conjunctivitis and keratitis which may lead to blindness.

      • Herpetic whitlow: finger infection from saliva.

    • Recurrent Infections:

      • Reactivation occurs (primarily in trigeminal ganglia).

      • Reactivation triggers include: stress, sunlight, febrile infection, local trauma, and menstruation.

      • HSV-1 vs HSV-2:

        • HSV-1: Above the belt via direct contact.

        • HSV-2: Below the belt via sexual contact.

      • Antivirals in prodromal phase: aciclovir, penciclovir, vidarabine.

Varicella-Zoster Virus (VZV) [HHV-3]

• Infections:

  • Chickenpox:

    • Mild, self-limiting disease (serious in adults).

    • 2-week incubation; symptoms: fever, papular rashes that become vesicular.

  • Shingles (Herpes zoster):

    • Reactivation in adults, causing lesions on chest wall and symptoms of fever/malaise.

    • Vesicular rashes are unilateral and painful; may lead to post-herpetic neuralgia.

• Complications:

  • Ophthalmic nerve involvement can cause eye lesions and blindness.

  • Ramsay Hunt syndrome leads to facial palsy and lesions in the auditory canal.

  • Triggering factors for shingles include immunosuppression and trauma.

  • The disease is transmissible through direct contact.

  • Treatment: systemic vidarabine and aciclovir.

  • Vaccines available for prevention.

Epstein-Barr Virus (EBV) [HHV-4]

• Latency: Primarily in B cells.

• Infections:

  • Glandular Fever (Infectious Mononucleosis):

    • 4-7 week incubation; affects lymphoid tissues, especially in teenagers; transmitted via saliva (known as kissing disease).

    • Symptoms: fever, lymphadenopathy, lymphocytosis, tonsillitis, splenomegaly.

• Associated Conditions:

  • Burkitt's Lymphoma: Severe malignant tumor in African children.

  • Nasopharyngeal Carcinoma: Highly malignant tumor in Southern China.

  • Hairy Leukoplakia: Infection causing white lesions on the tongue.

Cytomegalovirus (CMV) [HHV-5]

• Types of Infections:

  • Asymptomatic Infection: Occurs in infants; congenital infections can result in deafness/mental retardation.

  • Postnatal Infection: Severe multiorgan failure linked to pregnancy and immunosuppression.

  • Common in Patients: AIDS, transplant, and neoplasia patients.

Human Herpesvirus 6 [HHV-6]

• Blooms in B and T cells, particularly in immunocompromised patients.

• Infections:

  • Mononucleosis: Febrile disease in adults with cervical lymphadenopathy.

  • Exanthem subitum (Roseola infantum): Febrile disease in children causing a facial rash.

  • Strains cause erythematous papules in the oral cavity (Nagayama’s spots).

Orthomyxoviruses

• Types: Based on nucleocapsid protein (NP) and matrix protein (M).

• Infections:

  • Influenza: Symptoms include fever, myalgia, sore throat, cough; serious complications include pneumonia.

  • Avian Influenza: Symptoms are similar, with a potential for pneumonia and encephalitis.

  • Treatment: Amantadine and rimantadine for influenza; Tamiflu for bird flu.

Paramyxoviruses

• Parainfluenza Virus: Causes croup, bronchiolitis, pneumonia in children, and common cold in adults.

• Mumps Virus: Causes parotitis (mumps); preventable by MMR vaccine.

Measles Virus

• Symptoms: Fever, headache, nasal discharge, conjunctivitis, sore throat, Koplik's spots, and rash.

• Complications: Gangrenous stomatitis, SSPE, bronchopneumonia.

• Prevention: Live attenuated vaccine (MMR).

Picornaviruses

• Enteroviruses: Includes polioviruses, coxsackieviruses, rhinoviruses.

• Poliovirus: Causative agent of paralytic poliomyelitis, transmissible through contaminated water and direct contact.

• Prevention: Killed vaccine (Salk) or live attenuated vaccine (Sabin).

Coxsackieviruses

• Groups A and B:

  • Coxsackievirus A: Herpangina and Hand, Foot, and Mouth Disease (common in children).

  • Symptoms: sore throat, headache, malaise, tender parotid duct pain.

Rhinoviruses

• Common Cold: Transmitted via respiratory droplets.

Togaviruses

• Rubella Virus (German Measles): Transmitted via respiratory secretions; causes congenital rubella syndrome.

• Prevention: MMR vaccine.

Coronaviruses

• Identification: Named for crown-like spikes (“crown” in Latin) on envelope.

• Seven Human-Infecting Coronaviruses: e.g., SARS-CoV-2 (COVID-19).

Disease Impact**

• COVID-19: First reported in December 2019 in China; WHO declared a pandemic in March 2020.

  • Such symptoms may include dry cough, fever, and loss of taste/smell; severe cases may lead to respiratory distress.

  • Treatment: Remdesivir for severe cases; supportive care recommended.

  • Prevention: Vaccines (e.g., mRNA, viral vector-based).

Oral Mycology**

• Fungi Classification:

  • Molds: Filamentous fungi with hyphae structure.

  • Yeasts: Unicellular fungi; reproduce by budding (Candida albicans notable).

  • Dimorphic Fungi: Exist in two forms, molds in cultures and yeasts in tissues.

Human Mycoses**

• Superficial Mycoses: Infections of keratinized tissues and mucosae (ringworm, thrush).

• Subcutaneous Mycoses: Infections due to trauma, e.g., sporotrichosis, mycetoma.

• Systemic Mycoses: Fungal infections of internal organs from opportunistic organisms: coccidioidomycosis, blastomycosis, histoplasmosis.

  • Increasingly concerning for immunocompromised patients.

Candida Albicans**

• Major pathogenic yeast: can lead to superficial, mucosal, and systemic candidiasis.

  • Predisposing Factors: Chronic diseases, immunological disorders, malnutrition, age, smoking.

• Clinical Manifestations: Thrush, candidal vulvovaginitis, skin infections, and systemic infections resume.

Cryptococcus neoformans**

• Infection: Leading cause of cryptococcal meningitis; transmitted via respiratory droplets. Treatment: Amphotericin and fluconazole.

Filamentous and Dimorphic Fungi**

• Relevant to dentistry: Blastomyces dermatitidis, Histoplasma capsulatum, Coccidioides immitis; transmitted via the respiratory tract.

  • Lesions generally found in the lungs or occasionally skin and oral mucosa.

  • Treatment: Amphotericin and itraconazole.

References**

• Samaranayake L. (2024). Essential Microbiology for Dentistry. (6th edition). Churchill Livingstone Inc., London, United Kingdom. 424 p.

• evolve.elsevier.com