Viral Biology and Herpes Simplex Virus

Study Notes

Viruses enter animal cells through two mechanisms: receptor-mediated endocytosis and membrane fusion.

Viral genomes replicate independently of the host genome or integrate with the host genome.

Naked viruses are released through cell lysis, causing cell death and tissue damage.
Enveloped viruses acquire their envelope from the host cell membrane during assembly and exit, avoiding cell lysis and evading the host immune system.

The viral growth curve represents the change in the amount of infectious virus over time within a single infected cell.
The curve begins with the eclipse period, followed by exponential growth.

HSV causes a variety of infections including primary genital herpes, herpes labialis (cold sores), keratoconjunctivitis, and herpetic encephalitis.
Treatment for HSV includes acyclovir, oral acyclovir or valacyclovir, topical anesthetic sprays or gels, and analgesics and anti-inflammatory medication.
Corticosteroids are contraindicated for HSV infections.

EBV was discovered in 1964 by Michael Epstein and Yvonne Barr.
EBV is primarily spread through saliva.
Most EBV infections in childhood are asymptomatic.
Later in life, approximately 50% of infected individuals develop infectious mononucleosis (glandular fever).
EBV is linked to malignancies, including Burkitt lymphoma.
Classic symptoms of infectious mononucleosis include fever, pharyngitis, and lymphadenopathy.

CMV infects cells, causing them to enlarge and become multinucleated.
Initial CMV infection typically occurs during childhood.
Transmission of CMV occurs through direct contact with infected body fluids, sexual intercourse, blood transfusions, organ transplants, and congenital transmission.
Congenital CMV infection can lead to microcephaly, hepatosplenomegaly, and CNS infection.
CMV can also cause infectious mononucleosis, manifested as fever, pharyngitis, and lymphocytosis.

Clinical diagnosis is based on signs and symptoms.
Laboratory diagnosis involves testing for EBV (Monospot test, Paul-Bunnell test) and CMV (CMV-IgG and CMV-IgM).
CBC reveals marked lymphocytosis.
Abdominal ultrasonography is used to detect spleenomegaly.
Treatment includes analgesics, anti-inflammatory medication, antiviral drugs, and antibiotics for secondary bacterial infections.
Corticosteroids and enzymatic anti-inflammatory agents are typically avoided.

HHV-6 establishes a latent infection early in life.
HHV-6 primarily affects children between six months and two years of age.
Roseola infantum (Sixth disease) is characterized by a sudden high fever followed by a rash.

Molluscum contagiosum virus causes water warts, small raised lesions with a dimple in the center.
Variola virus causes smallpox, a disease eradicated in 1977.
Vaccinia virus is used in the smallpox vaccine.
Monkeypox virus causes mpox, a disease that can be transmitted through direct contact with infected lesions, sexual intercourse, or bites and scratches from infected animals.
Symptoms of mpox include rash, fever, sore throat, headache, muscle aches, and swollen lymph nodes.
Prevention of mpox includes the vaccinia virus vaccine.
Diagnosis of mpox is difficult, as it can resemble other infections.
Polymerase chain reaction (PCR) is the preferred laboratory test for mpox.