Overview
Herpes simplex virus (HSV) has two strains, type 1 and type 2, which are associated with the development of small vesicles with an erythematous base on the skin or mucous membranes (cold sores).
Pathophysiology
Infection can occur via close contact with an infected individual as the virus can enter through mucosal surfaces or breaks in the skin. It can infect neurones and travel via the axon to the nerve ganglion, where it can lay dormant for years. Over time, it can reactivate and spread peripherally across sensory nerves, leading to repeated symptoms in a dermatomal distribution (known as shingles).
Associations
Overview
HSV’s features depend on the infection site, its type, and the immunity of the host. In general, primary infections tend to be worse than subsequent infections, with more systemic upset (e.g. fever), longer symptoms, and an increased risk of complications.
It was previously thought that HSV-1 caused oral lesions and HSV-2 caused genital lesions, however, there is overlap. Its associations include:
- Mouth ulcers – cold sores
- Painful genital ulceration
- Encephalitis – >90% of cases are due to HSV-1
- Oesophagitis – if pharyngeal lesions spread to the oesophagus, causing painful swallowing and retrosternal pain
- Other: pneumonitis or disseminated disease – more common in immunocompromised or pregnant people
