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Herpes simplex virus
Medical expert of the article
Last reviewed: 06.07.2025
Infection caused by the herpes simplex virus may have several clinical forms, but is most often asymptomatic. Common clinical manifestations are vesicular rashes on the skin and mucous membranes. Sometimes there may be severe keratitis, meningoencephalitis or disseminated disease of the newborn. The herpes simplex virus is pathogenic for many species of animals - mice, rats, hamsters, guinea pigs, rabbits, dogs, monkeys, in which it usually causes fever and encephalitis (with intracerebral infection), and in rabbits also keratoconjunctivitis.
Since the virus has a dermoneurotropic effect, it can remain latent for a long time in the brain, epithelial cells, ganglia of the trigeminal and other nerves in the form of double-stranded circular forms of DNA in surviving animals and infected people.
The virus reproduces well in the chorion-allantoic membrane of chicken embryos, where 2-3 days after infection it forms convex white plaques visible to the naked eye. Giant cells with intranuclear inclusions are visible in print preparations from them. The virus easily reproduces in almost all widely used cell cultures, forming plaques in monolayers. Inclusion bodies are formed in infected cells, giant multinuclear cells appear, which then necrotize (cytopathic effect). Primary culture of rabbit kidney cells is especially suitable for infection.
[ Pathogenesis and symptoms of herpes simplex
When infected with the virus, its primary reproduction occurs in the epithelium of the mucous membrane of the mouth, pharynx or genitals. Then the virus penetrates the blood via the lymphatic route (generalized infection) and, having passed through the blood-brain barrier, can cause meningitis or encephalitis. In case of generalized herpes infection in newborns, death occurs, which is caused by multiple small-point necrosis and inflammatory foci in the internal organs. In case of recovery, a state of virus carriage is established, which changes throughout life and is manifested by transient herpes attacks, which can be provoked by various agents (solar radiation, fever, stress, spicy food, etc.).
Herpes virus type 1 can cause the development of the following clinical forms of the disease:
- acute herpetic (aphthous) stomatitis develops more often in primarily infected children, the incubation period is 3-5 days, damage to the mucous membrane heals in 2-3 weeks;
- herpetic eczema (Kaposi's rash, similar to chickenpox) is accompanied by fever and blistering lesions over most of the body surface, and is sometimes fatal;
- keratoconjunctivitis; with frequent relapses, irreversible corneal opacity and blindness may occur;
- meningoencephalitis; mortality is quite high, in case of recovery - persistent residual neurological changes;
- Herpes labialis - the most common form; clusters of merging blisters appear on the border of the mucous membrane and skin on the lips, turning into ulcers that heal without scars.
The herpes virus type 2 causes two main clinical forms of the disease: genital herpes (characterized by vesicular-ulcerative rashes on the skin and mucous membranes of the genitals, frequent relapses) and neonatal herpes (the child is infected during childbirth from a sick mother, the manifestations range from latent forms to generalization with a fatal outcome). Other localization of rashes is possible (wounds, fingers at dentists, etc.). Transplacental infection of the fetus with the herpes simplex virus is rare and causes the development of congenital deformities.
Immunity in herpes simplex
A child in the first 6 months of life usually has antibodies to the virus, acquired passively from the mother. Then they are lost, the child is most susceptible to herpes infection at the age of 6 months to 2 years. In the blood of those who have had the disease, antibodies are found that neutralize the virus, as well as specific IgA on the mucous membranes, but they do not prevent the persistence of the virus and the development of latent infection.
Epidemiology of viruses types 1 and 2
There is evidence that up to 70-90% of people are infected with the herpes virus type 1 and that it is present in the human body more constantly than any other virus. Primary infection occurs early in life. After the disappearance of maternal antibodies, the infection occurs as vesicular or aphthous stomatitis. The virus is no longer eliminated from the body, since it is not accessible to the action of antibodies. The herpes virus type 1 is transmitted by direct contact through saliva or through dishes contaminated with the saliva of the carrier. The source of infection for children is usually one of the parents with an active form of herpes.
The herpes simplex virus type 2 is transmitted sexually or during childbirth from a sick mother. It is spread as a typical venereal disease. The source of infection is only a person.
Laboratory diagnostics of herpes simplex
Diagnostics of herpes simplex can use virusoscopic, virological and serological methods. The material for the study is scrapings from the cornea, the contents of the vesicles, saliva, etc. Scrapings and smears taken from the base of fresh herpetic eruptions and stained according to Romanovsky-Eimse after immediate fixation in absolute alcohol contain giant multinucleated cells with intranuclear inclusions (Cowdry bodies).
To isolate the virus, cell cultures, chicken embryos, and laboratory animals are used. In infected cell cultures, plaques and a characteristic cytopathic effect are found; in chicken embryos, when infecting the chorionic-allantoic membrane, plaques are found, and the plaques formed by the herpes virus type 2 are larger than the plaques formed by the virus type 1. When infecting newborn mice in the brain, symptoms of encephalitis develop on the 2nd-6th day. Infection of the scarified cornea of a rabbit is very sensitive and specific for the herpes virus. Final identification is performed in a neutralization reaction on mice, chicken embryos, or cell cultures using standard antiherpetic immune sera of animals, as well as in an immunofluorescence reaction (IF).
In serodiagnostics, it is important to decide whether this is a primary disease or an exacerbation of a chronic infection. Therefore, paired sera are used, which are examined using RSK, RIF and IFM.
Treatment of herpes simplex
Specific treatment of herpes simplex is based on the use of chemotherapeutic agents - modified nucleosides that suppress viral replication, but are toxic and contribute to the emergence of virus strains resistant to them (adenine arabinoside, 5-iodo-2-deoxyuridine, acyclovir, etc.). Interferon inducers are effective, especially in the case of an acute course of the disease.