The controversial natural history of oral herpes simplex virus type 1 infection

The natural history of oral herpes simplex virus type 1 (HSV-1) infection in the immunocompetent host is complex and rich in controversial phenomena, namely the role of unapparent transmission in primary infection acquisition, the high frequency of asymptomatic primary and recurrent infections, the lack of immunogenicity of HSV-1 internalized in the soma (cell body) of the sensory neurons of the trigeminal ganglion, the lytic activity of HSV-1 in the soma of neurons that is inhibited in the sensory neurons of the trigeminal ganglion and often uncontrolled in the other neurons, the role of keratin in promoting the development of recurrence episodes in immunocompetent hosts, the virus–host Nash equilibrium, the paradoxical HSV-1-seronegative individuals who shed HSV-1 through saliva, the limited efficacy of anti-HSV vaccines, and why the oral route of infection is the least likely to produce severe complications. The natural history of oral HSV-1 infection is also a history of symbiosis between humans and virus that may switch from mutualism to parasitism and vice versa. This balance is typical of microorganisms that are highly coevolved with humans, and its knowledge is essential to oral healthcare providers to perform adequate diagnosis and provide proper individual-based HSV-1 infection therapy.