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Viral Infections

Viral replication is detected by Pattern-recognition receptors (PRRs), which trigger an immune response, leading to the production of restriction factors, like Type 1 Interferons.


Directly-acting antivirals (DAAs) are very specific in targeting viral infections.


HSV and VSV

Herpes Simplex Virus (HSV) presents with painful blisters and ulcers on genitals/mouth

  • Most commonly due to HSV 1

  • It can reoccur and present with prodromal tingling

Herpes labialis. Cold sore on the lower lip (cluster of fluid-filled blisters = very infectious). These infections may appear on the lips, nose or in surrounding areas. The sores may appear to be either weeping or dry, and may resemble a pimple, insect bite, or large chicken-pox lesion. Lesions typically heal after a few days to a week (or more); this varies among individuals. - Metju12 (https://commons.wikimedia.org/wiki/File:Herpes_labialis.jpg)

Varicella Zoster Virus (VZV) aka. Chickenpox, presents with a vesicular rash, accompanied by fever and fatigue, which dries up and crusts over within a week

  • It can re-activate later in life as Shingles - It remains latent in the spinal cord after the first infection, before reactivating along a dermatome - This presents with allodynia and hyperalgesia


N.B. Patients tend to develop Post-herpetic neuralgia (10% to 18%) once the rash resolves, in which they have persistent pain/burning in the affected area. Treatment is supportive, and most cases resolve within a few months. Early treatment with Aciclovir reduces the risk of this complication.

Photo of chicken pox - Camiloaranzales (https://commons.wikimedia.org/wiki/File:Varicela_Aranzales.jpg)

Both HSV and VZV are managed with Aciclovir or Valaciclovir. These drugs are insoluble in urine, so it can crystallise in the renal tubules when at a high dose, leading to renal failure.


CMV and EBV

Cytomegalovirus (CMV) is a major pathogen in solid organ and bone marrow transplant patients.

  • It can cause retinitis in immunocompromised patients


Epstein-Barr Virus (EBV) causes Infective Mononucleosis, aka. Glandular fever, which presents with a sore throat, macular rash, neck lymphadenopathy, fever, and malaise. It's diagnosed with the Monospot test.

“Exudative pharyngitis in the throat of a person with mononucleosis” © James Heilman, MD CC BY-SA 3.0 (https://creativecommons.org/licenses/by-sa/3.0/)

Both CMV and EBV are managed with Ganciclovir or Valganciclovir.



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