Alphaherpesviruses

Alphaherpesviruses are a subfamily of the Herpesviridae family, collectively known as Alphaherpesvirinae. They are characterized by relatively short replication cycles and a tropism for mucosal epithelium and neurons, with the ability to establish latent infections in sensory ganglia. The subfamily includes several genera, notably Simplexvirus and Varicellovirus, which encompass many viruses that infect humans and other mammals; additional genera exist in other animal hosts.

Genomes and biology of Alphaherpesviruses are defined by linear double-stranded DNA genomes, typically ranging in size from roughly 125 to 235 kilobases and encoding a substantial set of core replication and envelope proteins. The replication cycle is rapid in permissive cells, often causing pronounced cytopathic effects. A defining feature is the ability to establish latency in sensory neurons, such as the trigeminal or other ganglia, with periodic reactivation leading to recurrent disease.

In humans, the two primary genera are Simplexvirus, which includes herpes simplex viruses 1 and 2 (HSV-1 and HSV-2), and Varicellovirus, which includes varicella-zoster virus (VZV). HSV-1 commonly causes orolabial herpes and can contribute to conjunctival and other infections; HSV-2 is a common cause of genital herpes. VZV causes varicella (chickenpox) as a primary infection and can reactivate later in life to produce herpes zoster (shingles). Other Alphaherpesviruses infect animals, such as bovine herpesviruses and infectious laryngotracheitis virus in birds.

Transmission typically occurs through close contact or respiratory droplets. After mucosal entry, viruses replicate at the site of infection, cause local lesions, and may spread via the bloodstream before establishing latent infection in sensory ganglia. Antiviral therapies are available for several infections, and vaccines exist for VZV, while vaccines against HSV have not been widely adopted.