Bios Wk 4 - Herpes

Herpes Simplex Virus (HSV) Overview

Definition

  • Herpes Simplex Virus (HSV): An STI causing genital herpes and cold sores.

Types of HSV

  • HSV-2: Primarily causes genital herpes (90%).

  • HSV-1: Usually causes cold sores (10%) but can cause genital herpes.

Genital Herpes Transmission

Methods of Transmission

  • HSV-2: Transmitted sexually.

  • HSV-1: Can also be sexually transmitted.

  • Direct skin contact with lesions or fluids.

  • Transmission from pregnant people to neonates during delivery (neonatal herpes).

Pathogenesis of HSV

Infection Process

  • HSV-2 enters through mucous membranes or breaks in the skin.

  • After replication, it travels to sacral ganglia and remains latent for life.

Latency

  • During latency, viral genes are not expressed.

  • Possible reactivation triggered by stimuli (e.g., stress, pregnancy).

Neonatal Herpes

Incidence and Risks

  • Rare condition (5 in 100,000 in Canada).

  • Occurs mainly during vaginal delivery if pregnant individual is shedding the virus.

  • Usually not systemic unless the mother is infected for the first time late in pregnancy.

Timing of Transmission

  • Antepartum: 5%

  • Peripartum: 85%

  • Postpartum: 10%

Infection Impact

  • If maternal infection occurs before pregnancy, antibodies are transferred, reducing risk to the baby.

  • Infection during the first trimester is rare but can cause complications (miscarriage, congenital HSV).

  • High risk during late pregnancy (50% transmission risk).

Antibody Responses in Pregnancy

Immune Response

  • Primary immune response: B lymphocytes produce IgM.

  • Following IgM, they produce IgG, which is higher in avidity during reinfection.

  • Test IgG and IgM to differentiate between primary and recurrent HSV infection.

Clinical Manifestations of Neonatal HSV

Symptoms post-Birth

  • Irritability, lethargy, fever, poor feeding, vesicular skin lesions.

Disease Classification in Infants

Types of Infection

  1. Localized: Skin, eyes, mouth (45% cases) - good prognosis.

  2. CNS involvement (30%): May or may not have local symptoms.

  3. Disseminated infection (25%): Involves multiple organs leading to serious complications.

Varicella-Zoster Virus (VZV)

Overview

  • VZV, a member of the herpes virus family causes chickenpox and shingles.

  • Transmitted via droplets, it can lower T lymphocyte activity.

  • Latency occurs in sensory ganglia.

Congenital Varicella Syndrome (CVS)

  • Risk during pregnancy; infection rate of fetuses is 12-30%.

  • Serious effects include microcephaly, cataracts, and limb abnormalities.

  • Risks decrease later in pregnancy.

Measles, Mumps, Rubella (MMR)

Importance of Vaccination

  • Measles virus (Paramyxoviridae), Mumps virus (Paramyxoviridae), Rubella virus (Togaviridae).

  • Rubella can cause congenital rubella syndrome (CRS) leading to serious defects if contracted in early pregnancy.

Hepatitis Overview

Types of Hepatitis

  • Caused by toxins, drugs, or viruses (HAV, HBV, HCV).

Hepatitis B and C Transmission

  • Vertical transmission during delivery (HBV high risk).

  • Screening for hepatitis recommended in pregnancy.

Immunization During Pregnancy

Influence of Vaccination

  • Safe to immunize against influenza and other viruses.

  • Vaccines must be monitored for efficacy and safety.

Risks of Not Vaccinating

  • Increased morbidity for both the mother and infant.

  • Vaccination provides crucial antibody protection for the infant.